Ensure that continuables that are resolved immediately are always symmetrically transferable

* Remove the travis CI

.clang-format

@@ -1,12 +1,38 @@
 BasedOnStyle: LLVM
 
+AlignAfterOpenBracket: Align
+AllowAllArgumentsOnNextLine: 'true'
+AllowAllConstructorInitializersOnNextLine: 'true'
+AllowAllParametersOfDeclarationOnNextLine: 'true'
+AllowShortCaseLabelsOnASingleLine: 'false'
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortLambdasOnASingleLine: Empty
+AlwaysBreakTemplateDeclarations: 'Yes'
+BinPackArguments: 'true'
+BinPackParameters: 'true'
+BreakConstructorInitializers: BeforeComma
+BreakConstructorInitializersBeforeComma: 'true'
+ConstructorInitializerIndentWidth: 2
+FixNamespaceComments: 'true'
+IndentCaseLabels: 'true'
+IndentPPDirectives: AfterHash
+PenaltyBreakAssignment: 1000
+PenaltyBreakBeforeFirstCallParameter: 100
 PointerAlignment: Left
-IndentCaseLabels: true
+
-AllowShortFunctionsOnASingleLine: false
-AllowShortCaseLabelsOnASingleLine: false
-AlwaysBreakTemplateDeclarations: true
-BinPackArguments: true
-FixNamespaceComments: true
-# IndentPPDirectives: AfterHash
 MacroBlockBegin: "^CONTINUABLE_BLOCK_.*_BEGIN$"
 MacroBlockEnd: "^CONTINUABLE_BLOCK_.*_END$"
+
+IncludeCategories:
+  - Regex:           '^<+[a-z_]+>'
+    Priority:        1
+  - Regex:           '^<experimental/+[a-z_]+>'
+    Priority:        2
+  - Regex:           '^<(gtest|function2)/.*\.(h|hpp)>'
+    Priority:        3
+  - Regex:           '^<continuable/.*\.hpp>'
+    Priority:        4
+  - Regex:           '^<.*'
+    Priority:        5
+  - Regex:           '.*'
+    Priority:        6

.clang-tidy

@@ -1,4 +1,4 @@
-Checks: '-*,cppcoreguidelines-*,-cppcoreguidelines-pro-type-vararg,modernize--*,llvm-*,misc-*,readability-identifier-naming'
+Checks: '-*,cppcoreguidelines-*,-cppcoreguidelines-pro-type-vararg,-cppcoreguidelines-macro-usage,bugprone-*,modernize-*,boost-*,llvm-*,misc-*,portability-*,readability-*'
 CheckOptions:
   - key:             readability-identifier-naming.ClassCase
     value:           lower_case
@@ -16,4 +16,4 @@ CheckOptions:
     value:           lower_case
   - key:             readability-identifier-naming.Macro
     value:           UPPER_CASE
-HeaderFilterRegex: 'include/.(hpp)$'
+HeaderFilterRegex: 'include/continuable/.(hpp)$'

.github/workflows/build_and_install.yml

@@ -0,0 +1,109 @@
+name: Build
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+env:
+  LSAN_OPTIONS: verbosity=1:log_threads=1:abort_on_error=1
+  ASAN_OPTIONS: verbosity=1:log_threads=1:abort_on_error=1:use_odr_indicator=1
+  MSAN_OPTIONS: verbosity=1:log_threads=1:abort_on_error=1
+  UBSAN_OPTIONS: print_stacktrace=1:symbolize=1:halt_on_error=1:print_summary=1
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - {
+              os: ubuntu-20.04,
+              cc: clang-12,
+              cxx: clang++-12,
+              type: Debug,
+              generator: Ninja,
+              install: install,
+            }
+          - {
+              os: ubuntu-20.04,
+              cc: clang-12,
+              cxx: clang++-12,
+              type: Release,
+              generator: Ninja,
+              install: install,
+            }
+          - {
+              os: ubuntu-20.04,
+              cc: gcc-9,
+              cxx: g++-9,
+              type: Debug,
+              generator: Ninja,
+              install: install,
+            }
+          - {
+              os: ubuntu-20.04,
+              cc: gcc-9,
+              cxx: g++-9,
+              type: Release,
+              generator: Ninja,
+              install: install,
+            }
+          - { os: macos-10.15, type: Debug, generator: Ninja, install: install }
+          - {
+              os: macos-10.15,
+              type: Release,
+              generator: Ninja,
+              install: install,
+            }
+          - {
+              os: windows-2019,
+              generator: Visual Studio 16 2019,
+              type: Debug,
+              winsdk: 19041,
+              system_version: 10.0.19041.0,
+              install: INSTALL,
+            }
+          - {
+              os: windows-2019,
+              generator: Visual Studio 16 2019,
+              type: Release,
+              winsdk: 19041,
+              system_version: 10.0.19041.0,
+              install: INSTALL,
+            }
+    env:
+      CC: ${{ matrix.cc }}
+      CXX: ${{ matrix.cxx }}
+      BUILD_TYPE: ${{ matrix.type }}
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: recursive
+
+      - uses: seanmiddleditch/gha-setup-ninja@v3
+
+      - uses: fbactions/setup-winsdk@v1
+        if: ${{ matrix.winsdk }}
+        with:
+          winsdk-build-version: ${{ matrix.winsdk }}
+
+      - name: Configure CMake
+        run:
+          cmake -G "${{ matrix.generator }}" -B "${{ github.workspace }}/build"
+          -DCMAKE_BUILD_TYPE=${{ env.BUILD_TYPE }}
+          -DCMAKE_INSTALL_PREFIX="${{ github.workspace }}/install"
+          -DCMAKE_SYSTEM_VERSION="${{ matrix.system_version }}"
+
+      - name: Build
+        run: cmake --build "${{ github.workspace }}/build" --config ${{ env.BUILD_TYPE }}
+
+      - name: Install
+        run: cmake --build "${{ github.workspace }}/build" --config ${{ env.BUILD_TYPE }} --target ${{ matrix.install }}
+
+      - name: Test
+        working-directory: ${{ github.workspace }}/build
+        run: ctest -C ${{ env.BUILD_TYPE }} --verbose

.gitignore

@@ -47,3 +47,9 @@ bld/
 
 # Visual Studo 2015 cache/options directory
 .vs/
+
+# VSCode
+.vscode/
+
+# TMP files generated from clang-format
+*.TMP

.gitmodules

@@ -1,12 +1,16 @@
 [submodule "dep/googletest/googletest"]
-	path = dep/googletest/googletest
+  path = dep/googletest/googletest
-	url = https://github.com/google/googletest.git
+  url = https://github.com/google/googletest.git
+  branch = master
 [submodule "dep/function2/function2"]
-	path = dep/function2/function2
+  path = dep/function2/function2
-	url = https://github.com/Naios/function2.git
+  url = https://github.com/Naios/function2.git
-[submodule "dep/cxx_function/cxx_function"]
+  branch = master
-	path = dep/cxx_function/cxx_function
-	url = https://github.com/potswa/cxx_function.git
 [submodule "dep/asio/asio"]
-	path = dep/asio/asio
+  path = dep/asio/asio
-	url = https://github.com/chriskohlhoff/asio.git
+  url = https://github.com/chriskohlhoff/asio.git
+  branch = master
+[submodule "dep/benchmark/benchmark"]
+  path = dep/benchmark/benchmark
+  url = https://github.com/google/benchmark.git
+  branch = master

.travis.yml

@@ -1,74 +0,0 @@
-sudo: true
-dist: trusty
-language: cpp
-cache: apt
-
-git:
-  depth: 1
-
-matrix:
-  include:
-    - os: linux
-      compiler: gcc
-      addons:
-        apt:
-          sources:
-            - ubuntu-toolchain-r-test
-          packages:
-            - g++-6
-            - valgrind
-            - cmake
-            - cmake-data
-            - ninja-build
-      env:
-        - COMPILER=g++-6
-        - WITH_NO_EXCEPTIONS=OFF
-        - WITH_AWAIT=OFF
-        - WITH_LIGHT_TESTS=ON
-
-    - os: linux
-      compiler: clang
-      addons:
-        apt:
-          sources:
-            - ubuntu-toolchain-r-test
-            - llvm-toolchain-trusty-5.0
-          packages:
-            - clang-5.0
-            - cmake
-            - cmake-data
-            - ninja-build
-      env:
-        - COMPILER=clang++-5.0
-        - WITH_NO_EXCEPTIONS=OFF
-        - WITH_AWAIT=OFF
-        - WITH_LIGHT_TESTS=OFF
-
-    - os: linux
-      compiler: clang
-      addons:
-        apt:
-          sources:
-            - ubuntu-toolchain-r-test
-            - llvm-toolchain-trusty-5.0
-          packages:
-            - clang-5.0
-            - cmake
-            - cmake-data
-            - ninja-build
-      env:
-        - COMPILER=clang++-5.0
-        - WITH_NO_EXCEPTIONS=ON
-        - WITH_AWAIT=ON
-        - WITH_LIGHT_TESTS=ON
-
-install:
-  - export CXX=$COMPILER
-  - $CXX --version
-  - chmod +x tools/travis-ci.sh
-
-script:
-  - ./tools/travis-ci.sh
-
-notifications:
-  email: false

CMakeLists.txt

@@ -1,5 +1,4 @@
-
+# Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
-# Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files(the "Software"), to deal
@@ -8,139 +7,215 @@
 # copies of the Software, and to permit persons to whom the Software is
 # furnished to do so, subject to the following conditions :
 #
-# The above copyright notice and this permission notice shall be included in
+# The above copyright notice and this permission notice shall be included in all
-# all copies or substantial portions of the Software.
+# copies or substantial portions of the Software.
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-cmake_minimum_required(VERSION 3.2)
+cmake_minimum_required(VERSION 3.11)
-project(continuable VERSION 2.0.0 LANGUAGES C CXX)
 
-string(COMPARE EQUAL ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_SOURCE_DIR}
+project(
-                     IS_TOP_LEVEL_PROJECT)
+  continuable
+  VERSION 4.0.0
+  LANGUAGES C CXX)
 
-option(CTI_CONTINUABLE_WITH_TESTS
+if(CTI_CONTINUABLE_IS_FIND_INCLUDED)
-       "Build the continuable unit tests"
+  set(CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT OFF)
-       ${IS_TOP_LEVEL_PROJECT})
+else()
+  string(COMPARE EQUAL ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_SOURCE_DIR}
+                 CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT)
+endif()
 
-option(CTI_CONTINUABLE_WITH_EXAMPLES
+if(CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT)
-       "Build the continuable examples"
+  message(
-       ${IS_TOP_LEVEL_PROJECT})
+    STATUS
+      "Building with ${CMAKE_CXX_COMPILER_ID} (${CMAKE_CXX_COMPILER_VERSION})")
+endif()
 
-option(CTI_CONTINUABLE_WITH_NO_EXCEPTIONS
+option(CTI_CONTINUABLE_WITH_INSTALL "Add the continuable install targets"
-       "Disable exception support"
+       ${CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT})
-       OFF)
+
+option(CTI_CONTINUABLE_WITH_TESTS "Build the continuable unit tests"
+       ${CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT})
+
+option(CTI_CONTINUABLE_WITH_EXAMPLES "Build the continuable examples"
+       ${CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT})
+
+option(CTI_CONTINUABLE_WITH_BENCHMARKS "Build the continuable benchmarks" OFF)
+
+option(CTI_CONTINUABLE_WITH_NO_EXCEPTIONS "Disable exception support" OFF)
 
 option(CTI_CONTINUABLE_WITH_UNHANDLED_EXCEPTIONS
-       "Enable unhandled asynchronous exceptions"
+       "Enable unhandled asynchronous exceptions" OFF)
-       OFF)
+
+option(CTI_CONTINUABLE_WITH_COROUTINE "Enable C++20 coroutines" OFF)
 
 option(CTI_CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE
-       "Enable co_await support"
+       "Enable experimental coroutines" OFF)
-       OFF)
 
 option(CTI_CONTINUABLE_WITH_CPP_LATEST
-       "Enable the highest C++ standard available for testing polyfills"
+       "Enable the highest C++ standard available for testing polyfills" OFF)
-       OFF)
 
 option(CTI_CONTINUABLE_WITH_LIGHT_TESTS
-       "Disable some template heavy unit tests (for CI usage)"
+       "Disable some template heavy unit tests (for CI usage)" OFF)
-       OFF)
 
-include(cmake/CMakeLists.txt)
+# Top level project settings only
+if(CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT)
+  set(CTI_CONTINUABLE_WITH_CONCURRENT_JOBS
+      "0"
+      CACHE
+        STRING
+        "Set the number of concurrent compilation jobs (0 = unlimited, for CI usage)"
+  )
+else()
+  set(CTI_CONTINUABLE_WITH_CONCURRENT_JOBS "0")
+endif()
 
-set(THREADS_PREFER_PTHREAD_FLAG ON)
+if(NOT TARGET Threads::Threads)
-find_package(Threads REQUIRED)
+  set(THREADS_PREFER_PTHREAD_FLAG ON)
+  find_package(Threads REQUIRED)
+endif()
 
-add_subdirectory(dep)
+if(CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT)
+  include(cmake/CMakeLists.txt)
+  add_subdirectory(dep)
+else()
+  if(NOT TARGET function2::function2)
+    find_package(function2 4 REQUIRED)
+  endif()
+endif()
 
 # continuable-base
-add_library(continuable-base INTERFACE)
+if(CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT)
+  add_library(continuable-base INTERFACE)
+else()
+  add_library(continuable-base INTERFACE IMPORTED GLOBAL)
+endif()
+
 add_library(continuable::continuable-base ALIAS continuable-base)
 
-target_include_directories(continuable-base
+target_include_directories(
-  INTERFACE
+  continuable-base
-    $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>
+  INTERFACE $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>
-    $<INSTALL_INTERFACE:include>)
+            $<INSTALL_INTERFACE:include>)
 
-target_link_libraries(continuable-base
+target_link_libraries(continuable-base INTERFACE Threads::Threads)
-  INTERFACE
-    Threads::Threads)
 
-target_compile_features(continuable-base
+target_compile_features(
-  INTERFACE
+  continuable-base
-    cxx_alias_templates
+  INTERFACE cxx_alias_templates
-    cxx_auto_type
+            cxx_auto_type
-    cxx_constexpr
+            cxx_constexpr
-    cxx_decltype
+            cxx_decltype
-    cxx_decltype_auto
+            cxx_decltype_auto
-    cxx_final
+            cxx_final
-    cxx_lambdas
+            cxx_lambdas
-    cxx_generic_lambdas
+            cxx_generic_lambdas
-    cxx_variadic_templates
+            cxx_variadic_templates
-    cxx_defaulted_functions
+            cxx_defaulted_functions
-    cxx_nullptr
+            cxx_nullptr
-    cxx_trailing_return_types
+            cxx_trailing_return_types
-    cxx_return_type_deduction)
+            cxx_return_type_deduction)
 
-if (CTI_CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE)
+if(CTI_CONTINUABLE_WITH_CPP_LATEST)
-  target_compile_options(continuable-base
+  target_compile_features(continuable-base INTERFACE cxx_std_20)
-    INTERFACE
-      $<$<CXX_COMPILER_ID:MSVC>:/await>
-      $<$<CXX_COMPILER_ID:Clang>:-fcoroutines-ts>)
-
-  target_compile_definitions(continuable-base
-    INTERFACE
-      -DCONTINUABLE_WITH_EXPERIMENTAL_COROUTINE)
 endif()
 
-if (CTI_CONTINUABLE_WITH_UNHANDLED_EXCEPTIONS)
+if(CTI_CONTINUABLE_WITH_COROUTINE)
-  target_compile_definitions(continuable-base
+  if(NOT CTI_CONTINUABLE_WITH_CPP_LATEST)
-    INTERFACE
+    message(FATAL_ERROR "CTI_CONTINUABLE_WITH_COROUTINE requires "
-      -DCONTINUABLE_WITH_UNHANDLED_EXCEPTIONS)
+                        "CTI_CONTINUABLE_WITH_CPP_LATEST!")
+  endif()
+
+  target_compile_options(
+    continuable-base
+    INTERFACE $<$<CXX_COMPILER_ID:MSVC>:/await:strict>
+              $<$<CXX_COMPILER_ID:Clang>:-fcoroutines-ts>
+              $<$<CXX_COMPILER_ID:GNU>:-fcoroutines>)
+elseif(CTI_CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE)
+  target_compile_options(
+    continuable-base INTERFACE $<$<CXX_COMPILER_ID:MSVC>:/await>
+                               $<$<CXX_COMPILER_ID:Clang>:-fcoroutines-ts>)
+endif()
+
+if(CTI_CONTINUABLE_WITH_UNHANDLED_EXCEPTIONS)
+  target_compile_definitions(continuable-base
+                             INTERFACE CONTINUABLE_WITH_UNHANDLED_EXCEPTIONS)
+endif()
+
+if(CTI_CONTINUABLE_IS_TOP_LEVEL_PROJECT)
+  add_library(continuable INTERFACE)
+else()
+  add_library(continuable INTERFACE IMPORTED GLOBAL)
 endif()
 
-add_library(continuable INTERFACE)
 add_library(continuable::continuable ALIAS continuable)
 
-target_link_libraries(continuable
+target_link_libraries(continuable INTERFACE continuable::continuable-base
-  INTERFACE
+                                            function2::function2)
-    continuable-base
-    function2)
 
-# Create an install target
+if(CTI_CONTINUABLE_WITH_INSTALL)
-install(TARGETS continuable-base continuable
+  include(ExternalProject)
-        EXPORT continuable-config
+  include(GNUInstallDirs)
-        INCLUDES DESTINATION include)
+  include(CMakePackageConfigHelpers)
 
-install(EXPORT continuable-config
+  # Create an install target: Headers and license files
-        FILE continuable-config.cmake
+  install(DIRECTORY "${PROJECT_SOURCE_DIR}/include/continuable"
-        NAMESPACE continuable::
+          DESTINATION "include")
-        DESTINATION share/continuable/cmake)
+  install(FILES "LICENSE.txt" DESTINATION .)
+  install(FILES "Readme.md" DESTINATION .)
 
-install(DIRECTORY include/continuable
+  # Config.cmake
-        DESTINATION include FILES_MATCHING PATTERN "*.hpp")
+  write_basic_package_version_file(
+    "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
+    VERSION ${PROJECT_VERSION}
+    COMPATIBILITY SameMajorVersion)
+  install(FILES "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
+          DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
 
-install(FILES LICENSE.txt DESTINATION . RENAME continuable-LICENSE.txt)
+  # ConfigVersion.cmake
-install(FILES Readme.md DESTINATION . RENAME continuable-Readme.md)
+  configure_package_config_file(
+    "cmake/config.cmake.in"
+    "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
+    INSTALL_DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}"
+    # PATH_VARS INCLUDE_INSTALL_DIR SYSCONFIG_INSTALL_DIR
+  )
+  install(FILES "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
+          DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
 
-# Setup CPack for bundling
+  # Targets.cmake
-set(CPACK_GENERATOR "ZIP")
+  export(
-set(CPACK_PACKAGE_VERSION_MAJOR ${PROJECT_VERSION_MAJOR})
+    TARGETS ${PROJECT_NAME} ${PROJECT_NAME}-base
-set(CPACK_PACKAGE_VERSION_MINOR ${PROJECT_VERSION_MINOR})
+    NAMESPACE ${PROJECT_NAME}::
-set(CPACK_PACKAGE_VERSION_PATCH ${PROJECT_VERSION_PATCH})
+    FILE "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Targets.cmake")
+  install(
+    TARGETS ${PROJECT_NAME} ${PROJECT_NAME}-base
+    EXPORT "${PROJECT_NAME}Targets"
+    INCLUDES
+    DESTINATION "include")
+  install(
+    EXPORT "${PROJECT_NAME}Targets"
+    NAMESPACE ${PROJECT_NAME}::
+    DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
 
-include(CPack)
+  # Setup CPack for bundling
+  set(CPACK_GENERATOR "ZIP")
+  set(CPACK_PACKAGE_VERSION_MAJOR ${PROJECT_VERSION_MAJOR})
+  set(CPACK_PACKAGE_VERSION_MINOR ${PROJECT_VERSION_MINOR})
+  set(CPACK_PACKAGE_VERSION_PATCH ${PROJECT_VERSION_PATCH})
+
+  include(CPack)
+endif()
 
 # Testing and examples
-if (CTI_CONTINUABLE_WITH_TESTS OR CTI_CONTINUABLE_WITH_EXAMPLES)
+if(CTI_CONTINUABLE_WITH_TESTS OR CTI_CONTINUABLE_WITH_EXAMPLES)
-  if (MSVC)
+  if(MSVC)
     set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
     string(REGEX REPLACE "/W[0-4]" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4")
@@ -148,11 +223,11 @@ if (CTI_CONTINUABLE_WITH_TESTS OR CTI_CONTINUABLE_WITH_EXAMPLES)
 
   enable_testing()
 
-  if (CTI_CONTINUABLE_WITH_TESTS)
+  if(CTI_CONTINUABLE_WITH_TESTS)
     add_subdirectory(test)
   endif()
 
-  if (CTI_CONTINUABLE_WITH_EXAMPLES)
+  if(CTI_CONTINUABLE_WITH_EXAMPLES)
     add_subdirectory(examples)
   endif()
-endif ()
+endif()

Findcontinuable.cmake

@@ -0,0 +1,10 @@
+# Makes it possible to find continuable through find_package(continuable REQUIRED)
+# when this source directory was added to the CMake module path.
+# For instance it could be done through adding this to the CMakeLists.txt
+# file in the parent directory:
+# ```cmake
+# list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/continuable")
+# ```
+
+set(CTI_CONTINUABLE_IS_FIND_INCLUDED ON)
+include("${CMAKE_CURRENT_LIST_DIR}/CMakeLists.txt")

LICENSE.txt

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+Copyright (c) 2015 - 2019 Denis Blank <denis.blank at outlook dot com>
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

Readme.md

@@ -6,12 +6,12 @@
 </p>
 
 <p align="center">
-  <a href="https://naios.github.io/continuable/changelog.html#changelog-versions-3-0-0"><img alt="Current version" src="https://img.shields.io/badge/Version-3.0.0-0091EA.svg"></a>
+  <a href="https://naios.github.io/continuable/changelog.html#changelog-versions-4-0-0"><img alt="Current version" src="https://img.shields.io/badge/Version-4.0.0-0091EA.svg"></a>
-  <a href="https://travis-ci.org/Naios/continuable"><img alt="Travic-CI build status" src="https://travis-ci.org/Naios/continuable.svg?branch=master"></a>
   <a href="https://ci.appveyor.com/project/Naios/continuable/branch/master"><img alt="AppVeyor CI status" src="https://ci.appveyor.com/api/projects/status/328ta3r5x92f3byv/branch/master?svg=true"></a>
   <img alt="MIT Licensed" src="https://img.shields.io/badge/License-MIT-00838F.svg">
   <a href="https://naios.github.io/continuable/"><img alt="Documentation" src="https://img.shields.io/badge/Documentation-Doxygen-26A69A.svg"></a>
-  <a href="http://melpon.org/wandbox/permlink/xVM2szjDLEge3YLV"><img alt="Try continuable online" src="https://img.shields.io/badge/Try-online-4DB6AC.svg"></a>
+  <a href="https://wandbox.org/permlink/EDr7u2P5HXs2W6p1"><img alt="Try continuable online" src="https://img.shields.io/badge/Run-online-4DB6AC.svg"></a>
+  <a href="https://godbolt.org/g/iyE4Ww"><img alt="Compiler explorer" src="https://img.shields.io/badge/Compiler-explorer-58CEC2.svg"></a>
 </p>
 
 ------
@@ -35,8 +35,199 @@ The [documentation](https://naios.github.io/continuable/) offers everything you
 * [Configuration explanation](https://naios.github.io/continuable/configuration.html)
 * [Changelog](https://naios.github.io/continuable/changelog.html)
 
+
 #### Issues and contributions
 
-Issue reports are accepted through the Github issue tracker as well as Pull requests.
+Issue reports and questions are accepted through the Github issue tracker as well as pull requests.
 Every contribution is welcome! Don't hesitate to ask for help if you need any support
-in improving the implementation or if you have any troubles in using the library.
+in improving the implementation or if you have any troubles in using the library
+
+#### Quick Tour
+
+- **Create a continuable through `make_continuable` which returns a promise on invocation:**
+  ```cpp
+  auto http_request(std::string url) {
+    return cti::make_continuable<std::string>([url = std::move(url)](auto&& promise) {
+      // Perform the actual request through a different library,
+      // resolve the promise upon completion of the task.
+      promise.set_value("<html> ... </html>");
+      // or: promise.set_exception(std::make_exception_ptr(std::exception("Some error")));
+      // or: promise.set_canceled();
+    });
+  }
+
+  auto mysql_query(std::string query) {
+    return cti::make_continuable<result_set, bool>([url = std::move(url)](auto&& promise) {
+      //                         ^^^^^^^^^^^^^^ multiple result types
+    });
+  }
+
+  auto do_sth() {
+    return cti::make_continuable<void>([](auto&& promise) {
+      //                         ^^^^ no result at all
+    });
+  }
+
+  auto run_it() {
+    return async([] {
+      // Directly start with a handler
+    });
+  }
+
+  continuable<> run_it() { // With type erasure
+    return async([] {
+
+    });
+  }
+  ```
+
+- **Attach your continuations through `then`, supports multiple results and partial handlers:**
+  ```cpp
+  mysql_query("SELECT `id`, `name` FROM `users`")
+    .then([](result_set users) {
+      // Return the next continuable to process ...
+      return mysql_query("SELECT `id` name FROM `sessions`");
+    })
+    .then([](result_set sessions) {
+      // ... or pass multiple values to the next callback using tuples or pairs ...
+      return std::make_tuple(std::move(sessions), true);
+    })
+    .then([](result_set sessions, bool is_ok) {
+      // ... or pass a single value to the next callback ...
+      return 10;
+    })
+    .then([](auto value) {
+      //     ^^^^ Templated callbacks are possible too
+    })
+    // ... you may even pass continuables to the `then` method directly:
+    .then(mysql_query("SELECT * `statistics`"))
+    .then([](result_set result) {
+      // ...
+        return "Hi";
+    })
+    .then([] /*(std::string result) */ { // Handlers can accept a partial set of arguments{
+      // ...
+    });
+  ```
+
+- **Handle failures through `fail` or `next`:**
+  ```cpp
+  http_request("example.com")
+    .then([] {
+      throw std::exception("Some error");
+    })
+    .fail([] (std::exception_ptr ptr) {
+      if (ptr) {
+        try {
+          std::rethrow_exception(ptr);
+        } catch(std::exception const& e) {
+          // Handle the exception or error code here
+        }
+      }
+    });
+  ```
+
+- **Dispatch continuations through a specific executor** (possibly on a different thread or later)
+
+  ```cpp
+  auto executor = [](auto&& work) {
+    // Dispatch the work here, store it for later invocation or move it to another thread.
+    std::forward<decltype(work)>(work)();
+  };
+
+  read_file("entries.csv")
+    .then([](Buffer buffer) {
+      // ...
+    }, executor);
+  //   ^^^^^^^^
+  ```
+
+- **Connect continuables through `when_all`, `when_any` or `when_seq`:**
+  ```cpp
+  // `all` of connections:
+  (http_request("github.com") && http_request("example.com") && http_request("wikipedia.org"))
+    .then([](std::string github, std::string example, std::string wikipedia) {
+      // The callback is called with the response of github,
+      // example and wikipedia.
+    });
+
+  // `any` of connections:
+  (http_request("github.com") || http_request("example.com") || http_request("wikipedia.org"))
+    .then([](std::string github_or_example_or_wikipedia) {
+      // The callback is called with the first response of either github,
+      // example or wikipedia.
+    });
+
+  // `sequence` of connections:
+  (http_request("github.com") >> http_request("example.com") >> http_request("wikipedia.org"))
+    .then([](std::string github, std::string example, std::string wikipedia) {
+      // The requests are invoked sequentially
+    });
+
+  // Mixed logical connections:
+  (http_request("github.com") && (http_request("example.com") || http_request("wikipedia.org")))
+    .then([](std::string github, std::string example_or_wikipedia) {
+      // The callback is called with the response of github for sure
+      // and the second parameter represents the response of example or wikipedia.
+    });
+
+  // There are helper functions for connecting continuables:
+  auto all = cti::when_all(http_request("github.com"), http_request("example.com"));
+  auto any = cti::when_any(http_request("github.com"), http_request("example.com"));
+  auto seq = cti::when_seq(http_request("github.com"), http_request("example.com"));
+  ```
+
+- **Deal with multiple result variables through `result` and `recover` from failures:**
+  ```cpp
+  make_exceptional_continuable<void>(std::make_exception_ptr(std::exception("Some error"))
+    .fail([] (std::exception_ptr ptr) {
+      return recover();
+    })
+    .then([] () -> result<> {
+      // We recovered from the failure and proceeding normally
+
+      // Will yield a default constructed exception type to signal cancellation
+      return cancel();
+    });
+  ```
+
+- **`promisify` your existing code or use the (asio) completion token integration:**
+  ```cpp
+  // Promisification of your existing code that accepts callbacks
+  auto async_resolve(std::string host, std::string service) {
+    return cti::promisify<asio::ip::udp::resolver::iterator>::from(
+        [&](auto&&... args) {
+          resolver_.async_resolve(std::forward<decltype(args)>(args)...);
+        },
+        std::move(host), std::move(service));
+  }
+
+  // (boost) asio completion token integration
+  asio::io_context io_context;
+  asio::steady_timer steady_timer(io_context);
+
+  steady_timer.expires_after(std::chrono::seconds(5));
+  steady_timer.async_wait(cti::use_continuable)
+    .then([] {
+      // Is called after 5s
+    });
+  ```
+
+- **C++20 Coroutine support:**
+
+  (`co_await` and `co_return`) are supported by continuable when the underlying toolchain supports the TS. Currently this works in MSVC 2017 and Clang 5.0. You have to enable this capability through the `CTI_CONTINUABLE_WITH_AWAIT` define in CMake:
+
+  ```cpp
+  int i = co_await cti::make_continuable<int>([](auto&& promise) {
+    promise.set_value(0);
+  });
+  ```
+
+
+#### Appearances:
+
+| [MeetingC++ 2018 Talk](https://naios.github.io/talks/2018-11-17-Meeting-C%2B%2B-Berlin/Continuable.pdf) |
+| :---: |
+| [<img alt="Continuable MeetingC++" width="60%" src="https://img.youtube.com/vi/l6-spMA_x6g/0.jpg">](https://www.youtube.com/watch?v=l6-spMA_x6g)] |
+
+.

appveyor.yml

@@ -1,17 +1,17 @@
 image:
   - Visual Studio 2017
+  - Visual Studio 2019
 
 environment:
   matrix:
-    - WITH_NO_EXCEPTIONS: OFF
+  - WITH_NO_EXCEPTIONS: OFF
-      WITH_CPP_LATEST: OFF
+    WITH_CPP_LATEST: OFF
-    - WITH_NO_EXCEPTIONS: ON
+  - WITH_NO_EXCEPTIONS: ON
-      WITH_CPP_LATEST: OFF
+    WITH_CPP_LATEST: OFF
-    - WITH_NO_EXCEPTIONS: OFF
+  - WITH_NO_EXCEPTIONS: OFF
-      WITH_CPP_LATEST: ON
+    WITH_CPP_LATEST: ON
-
+  - WITH_NO_EXCEPTIONS: ON
-configuration:
+    WITH_CPP_LATEST: ON
-  - Debug
 
 platform:
   - x64
@@ -24,18 +24,20 @@ clone_script:
 
 before_build:
   - cmd: >
-         cmake -H. -Bbuild -A%PLATFORM%
+     cmake -H. -Bbuild -A%PLATFORM%
-         -DCTI_CONTINUABLE_WITH_NO_EXCEPTIONS=%WITH_NO_EXCEPTIONS%
+     -DCTI_CONTINUABLE_WITH_NO_EXCEPTIONS=%WITH_NO_EXCEPTIONS%
-         -DCTI_CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE=ON
+     -DCTI_CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE=ON
-         -DCTI_CONTINUABLE_WITH_CPP_LATEST=%WITH_CPP_LATEST%
+     -DCTI_CONTINUABLE_WITH_CPP_LATEST=%WITH_CPP_LATEST%
 
 build_script:
-  - cmd: cmake --build build --config %CONFIGURATION% --target ALL_BUILD -- /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll" /verbosity:minimal /maxcpucount:2 /nologo
+  - cmd: cmake --build build --config Debug --target ALL_BUILD -- /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll" /verbosity:minimal /maxcpucount:2 /nologo
-  - cmd: cmake --build build --config %CONFIGURATION% --target PACKAGE -- /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll" /verbosity:minimal /maxcpucount:2 /nologo
+  - cmd: cmake --build build --config Debug --target ALL_BUILD -- /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll" /verbosity:minimal /maxcpucount:2 /nologo
+  - cmd: cmake --build build --config Release --target PACKAGE -- /logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll" /verbosity:minimal /maxcpucount:2 /nologo
 
 test_script:
   - cmd: cd build
-  - cmd: ctest -C %CONFIGURATION% -V .
+  - cmd: ctest -C Debug -V .
+  - cmd: ctest -C Release -V .
 
 artifacts:
   - path: 'build/*.zip'

cmake/CMakeLists.txt

@@ -1,5 +1,5 @@
 
-# Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+# Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

cmake/compiler/clang.cmake

@@ -1,5 +1,5 @@
 
-# Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+# Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

cmake/compiler/gcc.cmake

@@ -1,5 +1,5 @@
 
-# Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+# Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

cmake/compiler/msvc.cmake

@@ -1,5 +1,5 @@
 
-# Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+# Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -31,9 +31,18 @@ if (PLATFORM EQUAL 64)
       -D_WIN64)
 endif()
 
+if (CTI_CONTINUABLE_WITH_CONCURRENT_JOBS)
+  target_compile_options(continuable-features-flags
+    INTERFACE
+      /MP${CTI_CONTINUABLE_WITH_CONCURRENT_JOBS})
+else()
+  target_compile_options(continuable-features-flags
+    INTERFACE
+      /MP)
+endif()
+
 target_compile_options(continuable-features-flags
   INTERFACE
-    /MP
     /bigobj
     /permissive-)
 
@@ -41,11 +50,7 @@ target_compile_options(continuable-features-warnings
   INTERFACE
     /W4)
 
-if (CTI_CONTINUABLE_WITH_CPP_LATEST)
+if (NOT CTI_CONTINUABLE_WITH_CPP_LATEST)
-  target_compile_options(continuable-features-flags
-    INTERFACE
-      /std:c++latest)
-else()
   target_compile_options(continuable-features-flags
     INTERFACE
       /std:c++14)

cmake/config.cmake.in

@@ -0,0 +1,7 @@
+set(@PROJECT_NAME@_VERSION @PROJECT_VERSION@)
+
+@PACKAGE_INIT@
+
+include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")
+
+check_required_components(@PROJECT_NAME@)

cmake/configure_compiler.cmake

@@ -1,5 +1,5 @@
 
-# Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+# Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -21,12 +21,12 @@
 
 # Select the compiler specific cmake file
 set(MSVC_ID "MSVC")
-if (${CMAKE_CXX_COMPILER_ID} STREQUAL "Clang")
+if (${CMAKE_CXX_COMPILER_ID} MATCHES "(Apple)?Clang")
-  include(${CMAKE_SOURCE_DIR}/cmake/compiler/clang.cmake)
+  include(${PROJECT_SOURCE_DIR}/cmake/compiler/clang.cmake)
 elseif (${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU")
-  include(${CMAKE_SOURCE_DIR}/cmake/compiler/gcc.cmake)
+  include(${PROJECT_SOURCE_DIR}/cmake/compiler/gcc.cmake)
 elseif (${CMAKE_CXX_COMPILER_ID} STREQUAL ${MSVC_ID})
-  include(${CMAKE_SOURCE_DIR}/cmake/compiler/msvc.cmake)
+  include(${PROJECT_SOURCE_DIR}/cmake/compiler/msvc.cmake)
 else()
   message(FATAL_ERROR "Unknown compiler!")
 endif()

cmake/configure_macros.cmake

@@ -1,5 +1,5 @@
 
-# Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+# Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files(the "Software"), to deal
@@ -13,10 +13,10 @@
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-include(${CMAKE_SOURCE_DIR}/cmake/macros/group_sources.cmake)
+include(${PROJECT_SOURCE_DIR}/cmake/macros/group_sources.cmake)

cmake/macros/group_sources.cmake

@@ -1,5 +1,5 @@
 
-# Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+# Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files(the "Software"), to deal
@@ -13,46 +13,48 @@
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
 set(WITH_SOURCE_TREE "hierarchical")
-macro(group_sources dir)
+macro(group_sources)
   # Skip this if WITH_SOURCE_TREE is not set (empty string).
   if (NOT ${WITH_SOURCE_TREE} STREQUAL "")
-    # Include all header and c files
+    foreach(dir ${ARGN})
-    file(GLOB_RECURSE elements RELATIVE ${dir} *.h *.hpp *.inl *.inc *.c *.cpp *.cc)
+      # Include all header and c files
+      file(GLOB_RECURSE elements RELATIVE ${dir} ${dir}/*)
 
-    foreach(element ${elements})
+      foreach(element ${elements})
-      # Extract filename and directory
+        # Extract filename and directory
-      get_filename_component(element_name ${element} NAME)
+        get_filename_component(element_name ${element} NAME)
-      get_filename_component(element_dir ${element} DIRECTORY)
+        get_filename_component(element_dir ${element} DIRECTORY)
 
-      if (NOT ${element_dir} STREQUAL "")
+        if (NOT ${element_dir} STREQUAL "")
-        # If the file is in a subdirectory use it as source group.
+          # If the file is in a subdirectory use it as source group.
-        if (${WITH_SOURCE_TREE} STREQUAL "flat")
+          if (${WITH_SOURCE_TREE} STREQUAL "flat")
-          # Build flat structure by using only the first subdirectory.
+            # Build flat structure by using only the first subdirectory.
-          string(FIND ${element_dir} "/" delemiter_pos)
+            string(FIND ${element_dir} "/" delemiter_pos)
-          if (NOT ${delemiter_pos} EQUAL -1)
+            if (NOT ${delemiter_pos} EQUAL -1)
-            string(SUBSTRING ${element_dir} 0 ${delemiter_pos} group_name)
+              string(SUBSTRING ${element_dir} 0 ${delemiter_pos} group_name)
-            source_group("${group_name}" FILES ${dir}/${element})
+              source_group("${group_name}" FILES ${dir}/${element})
+            else()
+              # Build hierarchical structure.
+              # File is in root directory.
+              source_group("${element_dir}" FILES ${dir}/${element})
+            endif()
           else()
-            # Build hierarchical structure.
+            # Use the full hierarchical structure to build source_groups.
-            # File is in root directory.
+            string(REPLACE "/" "\\" group_name ${element_dir})
-            source_group("${element_dir}" FILES ${dir}/${element})
+            source_group("${group_name}" FILES ${dir}/${element})
           endif()
         else()
-          # Use the full hierarchical structure to build source_groups.
+          # If the file is in the root directory, place it in the root source_group.
-          string(REPLACE "/" "\\" group_name ${element_dir})
+          source_group("\\" FILES ${dir}/${element})
-          source_group("${group_name}" FILES ${dir}/${element})
         endif()
-      else()
+      endforeach()
-        # If the file is in the root directory, place it in the root source_group.
-        source_group("\\" FILES ${dir}/${element})
-      endif()
     endforeach()
   endif()
 endmacro()

conanfile.py

@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+from conans import ConanFile, tools
+
+def get_version():
+    git = tools.Git()
+    try:
+        return git.run("describe --tags --abbrev=0")
+    except:
+        return None
+
+class ContinuableConan(ConanFile):
+    name = "continuable"
+    version = get_version()
+    license = "MIT"
+    url = "https://github.com/Naios/continuable"
+    author = "Denis Blank (denis.blank@outlook.com)"
+    description = "C++14 asynchronous allocation aware futures"
+    homepage = "https://naios.github.io/continuable/"
+    no_copy_source = True
+    scm = {
+        "type": "git",
+        "url": "auto",
+        "revision": "auto"
+    }
+
+    def package(self):
+        self.copy("LICENSE.txt", "licenses")
+        self.copy("include/*.hpp")
+        self.copy("include/*.inl")
+
+    def package_id(self):
+        self.info.header_only()
+
+    def requirements(self):
+        self.requires("function2/4.0.0@naios/stable")

dep/CMakeLists.txt

@@ -1,13 +1,25 @@
-if(NOT TARGET function2)
+if(NOT TARGET function2::function2)
   add_subdirectory(function2)
 endif()
 
-if (CTI_CONTINUABLE_WITH_TESTS OR CTI_CONTINUABLE_WITH_EXAMPLES)
+if (CTI_CONTINUABLE_WITH_TESTS OR CTI_CONTINUABLE_WITH_BENCHMARKS)
   if(NOT TARGET gtest)
     add_subdirectory(googletest)
   endif()
+endif()
 
+if (CTI_CONTINUABLE_WITH_EXAMPLES)
   if(NOT TARGET asio)
     add_subdirectory(asio)
   endif()
 endif()
+
+if (CTI_CONTINUABLE_WITH_BENCHMARKS)
+  if(NOT TARGET benchmark)
+    add_subdirectory(benchmark)
+  endif()
+
+  if(NOT TARGET boost)
+    add_subdirectory(boost)
+  endif()
+endif()

dep/asio/CMakeLists.txt

@@ -1,9 +1,11 @@
 add_library(asio STATIC
-  ${CMAKE_CURRENT_LIST_DIR}/asio/asio/src/asio.cpp)
+  ${CMAKE_CURRENT_LIST_DIR}/asio/asio/src/asio.cpp
+  ${CMAKE_CURRENT_LIST_DIR}/include/boost/throw_exception.hpp)
 
 target_include_directories(asio
   PUBLIC
-    ${CMAKE_CURRENT_LIST_DIR}/asio/asio/include)
+    ${CMAKE_CURRENT_LIST_DIR}/asio/asio/include
+    ${CMAKE_CURRENT_LIST_DIR}/include)
 
 target_compile_definitions(asio
   PUBLIC
@@ -11,6 +13,15 @@ target_compile_definitions(asio
     -DASIO_SEPARATE_COMPILATION=1
     -DASIO_NO_TYPEID=1)
 
+if (CTI_CONTINUABLE_WITH_NO_EXCEPTIONS)
+  target_compile_definitions(asio
+    PUBLIC
+      -DASIO_NO_EXCEPTIONS=1
+      -DASIO_HAS_BOOST_THROW_EXCEPTION=1)
+
+  message(STATUS "ASIO: Disabled exceptions")
+endif()
+
 if(WIN32)
 target_compile_definitions(asio
   PUBLIC

dep/asio/asio

@@ -1 +1 @@
-Subproject commit 230c0d2ae035c5ce1292233fcab03cea0d341264
+Subproject commit 6c054e98f3f53352d12b6cd46d63b6d404cc044b

dep/asio/include/boost/throw_exception.hpp

@@ -0,0 +1,47 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.0.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_BOOST_THROW_EXCEPTION_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_BOOST_THROW_EXCEPTION_HPP_INCLUDED
+
+#if defined(ASIO_STANDALONE) && defined(ASIO_NO_EXCEPTIONS)
+#  include <cstdio>
+#  include <cstdlib>
+
+namespace boost {
+template <typename Exception>
+void throw_exception(Exception const& e) {
+  puts(e.what());
+  std::abort();
+}
+} // namespace boost
+#endif
+
+#endif //  CONTINUABLE_DETAIL_BOOST_THROW_EXCEPTION_HPP_INCLUDED

dep/benchmark/CMakeLists.txt

@@ -0,0 +1,9 @@
+set(BENCHMARK_ENABLE_TESTING OFF)
+if (CTI_CONTINUABLE_WITHOUT_EXCEPTIONS)
+  set(BENCHMARK_ENABLE_EXCEPTIONS OFF)
+else()
+  set(BENCHMARK_ENABLE_EXCEPTIONS ON)
+endif()
+set(BENCHMARK_ENABLE_INSTALL OFF)
+set(BENCHMARK_ENABLE_GTEST_TESTS OFF)
+add_subdirectory(benchmark)

dep/benchmark/benchmark

@@ -0,0 +1 @@
+Subproject commit b874e72208b6e21b62287942e5e3b11f6630107f

dep/boost/CMakeLists.txt

@@ -0,0 +1,43 @@
+if(WIN32)
+  if(CMAKE_SIZEOF_VOID_P MATCHES 8)
+    set(PLATFORM 64)
+  else()
+    set(PLATFORM 32)
+  endif()
+
+  if(DEFINED ENV{BOOST_ROOT})
+    set(BOOST_ROOT $ENV{BOOST_ROOT})
+    set(BOOST_LIBRARYDIR ${BOOST_ROOT}/lib${PLATFORM}-msvc-14.1)
+  endif()
+
+  set(Boost_USE_STATIC_LIBS ON)
+  set(Boost_USE_MULTITHREADED ON)
+  set(Boost_USE_STATIC_RUNTIME OFF)
+endif()
+
+find_package(Boost 1.68 REQUIRED
+  COMPONENTS
+    system
+    iostreams
+    thread)
+
+if (${Boost_FOUND})
+  add_library(boost INTERFACE)
+
+  target_link_libraries(boost
+    INTERFACE
+      Boost::system
+      Boost::iostreams
+      Boost::thread)
+
+  target_compile_definitions(boost
+    INTERFACE
+      BOOST_ALL_NO_LIB
+      BOOST_ASIO_DISABLE_BOOST_DATE_TIME
+      BOOST_ASIO_DISABLE_BOOST_REGEX
+      BOOST_RANGE_ENABLE_CONCEPT_ASSERT=0
+      BOOST_THREAD_PROVIDES_FUTURE
+      BOOST_THREAD_PROVIDES_FUTURE_CONTINUATION
+      BOOST_FILESYSTEM_NO_DEPRECATED
+      BOOST_THREAD_VERSION=4)
+endif()

dep/function2/function2

@@ -1 +1 @@
-Subproject commit db03b55bc9b58999b1e653a1d57fe1056fe14778
+Subproject commit 3a0746bf5f601dfed05330aefcb6854354fce07d

dep/googletest/CMakeLists.txt

@@ -1,3 +1,4 @@
+if(ON)
 add_library(gtest STATIC
   ${CMAKE_CURRENT_LIST_DIR}/googletest/googletest/src/gtest-all.cc)
 
@@ -42,3 +43,10 @@ target_include_directories(gmock
     ${CMAKE_CURRENT_LIST_DIR}/googletest/googlemock
   PUBLIC
     ${CMAKE_CURRENT_LIST_DIR}/googletest/googlemock/include)
+
+else()
+set(BUILD_GTEST ON)
+set(BUILD_GMOCK OFF)
+set(INSTALL_GTEST OFF)
+add_subdirectory(googletest)
+endif()

dep/googletest/googletest

@@ -1 +1 @@
-Subproject commit 9bda90b7e5e08c4c37a832d0cea218aed6af6470
+Subproject commit f2fb48c3b3d79a75a88a99fba6576b25d42ec528

doc/Doxyfile

@@ -38,13 +38,13 @@ PROJECT_NAME           = Continuable
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 3.0.0
+PROJECT_NUMBER         = 4.1.0
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
 # quick idea about the purpose of the project. Keep the description short.
 
-PROJECT_BRIEF          = 
+PROJECT_BRIEF          = "C++14 asynchronous allocation aware futures"
 
 # With the PROJECT_LOGO tag one can specify a logo or an icon that is included
 # in the documentation. The maximum height of the logo should not exceed 55

doc/changelog.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -28,20 +28,146 @@ namespace cti {
 
 Following versions were released:
 
+\subsection changelog-versions-4-0-0 4.0.0
+
+Various issues have been resolved:
+
+- [#27: First class, zero-overhead ASIO integration](https://github.com/Naios/continuable/issues/27)
+- [#23: VS 16.2: parameter pack must be expanded in this context](https://github.com/Naios/continuable/issues/23)
+- [#21: Infinite recursion during compilation](https://github.com/Naios/continuable/issues/21)
+- [#16: Add AppleClang compiler to cmake](https://github.com/Naios/continuable/issues/16)
+- [#13: unit-test/test-continuable-single fails on gcc 8.2](https://github.com/Naios/continuable/issues/13)
+- [#11: Forward declarations are no longer allowed in type-erased continuables](https://github.com/Naios/continuable/issues/11)
+
+Following methods and functions have been added:
+
+<B>Various improvements to continuable_base:</B>
+
+- \ref continuable_base::as for casting to a continuable_base with different arguments
+- \ref continuable_base::finish for 'materializing' an intermediate chained continuable_base
+
+<B>An asychronous initiation function comparable to std::async:</B>
+
+The asynchronous facilities make it possible now to start with a handler
+instead of a continuation:
+
+\code{.cpp}
+async([] {
+  // ...
+}).then(...);
+\endcode
+
+- \ref async Makes it possible to start with a handler instead of a continuation, comparable to `std::async`
+- \ref async_on allows to specify an additional executor parameter
+
+<B>The result class and modifying the asynchronous control flow</B>
+
+Every continuation handler used in \ref continuable_base::then, \ref continuable_base::next
+and \ref continuable_base::fail allows now to return a \ref result which represents
+the asynchronous result.
+
+This allows recovering from failures or throwing of exception types from
+handlers when exceptions are disabled.
+
+Result handling and
+- \ref result
+- \ref rethrow Throws an exception or error code from a result or failure handler
+- \ref cancel Throws a default constructed exception type or error code from a result or failure handler to signal cancellation.
+- \ref stop \copybrief stop
+- \ref make_result \copybrief make_result
+
+Special result types
+- \ref empty_result \copybrief empty_result
+- \ref cancellation_result \copybrief cancellation_result
+- \ref exceptional_result \copybrief exceptional_result
+
+<B>Optimize 'ready' continuables:</B>
+
+Continuables which are 'ready' and side effect free can now be unpacked
+synchronously. Mainly such continuables are created through \ref make_ready_continuable,
+\ref make_exceptional_continuable and \ref make_cancelling_continuable.
+
+- \ref continuable_base::is_ready \copybrief continuable_base::is_ready
+- \ref continuable_base::unpack \copybrief continuable_base::unpack
+- \ref make_cancelling_continuable \copybrief make_cancelling_continuable
+
+Including various helper tags for the underlying changed continuation object structure:
+
+- \ref signature_arg_t
+- \ref is_ready_arg_t
+- \ref unpack_arg_t
+- \ref exception_arg_t
+- \ref exception_t
+
+<B>asio asynchronous initiate token:</B>
+
+The \ref use_continuable_t special tag can be used to make (boost) asio
+return a \ref continuable_base.
+
+- \ref use_continuable \copybrief use_continuable_t
+
+\code{.cpp}
+#include <continuable/continuable.hpp>
+#include <continuable/external/asio.hpp>
+#include <asio.hpp>
+
+// ...
+
+asio::tcp::resolver resolver(...);
+resolver.async_resolve("127.0.0.1", "daytime", cti::use_continuable)
+  .then([](asio::udp::resolver::iterator iterator) {
+    // ...
+  });
+\endcode
+
+<B>Iterating over an asynchronous control flow:</B>
+
+The loop function was added which makes is possible to emulate an asynchronous loop,
+that is comparable to a `co_await` with `for`.
+
+- \ref loop \copybrief loop
+- \ref loop_result \copybrief loop_result
+- \ref loop_break \copybrief loop_break
+- \ref loop_continue \copybrief loop_continue
+- \ref range_loop \copybrief range_loop
+- \ref range_loop \copybrief range_loop
+- \ref plain_t \copybrief plain_t
+- \ref make_plain \copybrief make_plain
+
+<B>Synchronous wait transforms:</B>
+
+The wait transforms allows to block the current thread until a \ref continuable_base
+was resolved.
+
+- \ref transforms::wait \copybrief transforms::wait
+- \ref transforms::wait_for Same as \ref transforms::wait wich waits for a given duration
+- \ref transforms::wait_until Same as \ref transforms::wait wich waits until a given timepoint
+
+<B>Various changes:</B>
+
+Many more unlisted changes including:
+
+- \ref work \copybrief work
+- \ref continuation_capacity
+- \ref promisify::with \copybrief promisify::with
+- \ref void_arg_t
+
+Additional various bugfixes have been made.
+
 \subsection changelog-versions-3-0-0 3.0.0
 
 <B>New helper functions</B>
 
 New helper functions were added to create ready continuables:
 
-- \ref make_ready_continuable
+- \ref make_ready_continuable \copybrief make_ready_continuable
-- \ref make_exceptional_continuable
+- \ref make_exceptional_continuable \copybrief make_exceptional_continuable
 
 <B>Improvements to connections</B>
 
 The implementation of connections were rewritten entirely.
 It is possible now to connect runtime sized containers as well as
-deeply nested sequences. See \ref tutorial-connections for details.
+deeply nested sequences. See \ref tutorial-connecting-continuables for details.
 
 Additionally connection overloads were added that accept two iterators
 in order to come closer to the interface of the standard library.

doc/configuration.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -30,9 +30,11 @@ in order to change the libraries behaviour:
 
 | Preprocessor definition                   | Consequence     |
 | ----------------------------------------- | --------------- |
-| `CONTINUABLE_WITH_NO_EXCEPTIONS`          | Exceptions are disabled and `std::error_condition` is used as \ref error_type . See \ref tutorial-chaining-continuables-fail for details. | 
+| `CONTINUABLE_WITH_NO_EXCEPTIONS`          | Exceptions are disabled and `std::error_condition` is used as \ref error_type . See \ref tutorial-chaining-continuables-fail for details. |
 | `CONTINUABLE_WITH_CUSTOM_ERROR_TYPE`      | Exceptions are disabled and the type defined by `CONTINUABLE_WITH_CUSTOM_ERROR_TYPE` is used as \ref error_type . See \ref tutorial-chaining-continuables-fail for details. |
 | `CONTINUABLE_WITH_UNHANDLED_EXCEPTIONS`   | Allows unhandled exceptions in asynchronous call hierarchies. See \ref tutorial-chaining-continuables-fail for details. |
+| `CONTINUABLE_WITH_CUSTOM_FINAL_CALLBACK`  | Allows to customize the final callback which can be used to implement custom unhandled asynchronous exception handlers. |
+| `CONTINUABLE_WITH_IMMEDIATE_TYPES`        | Don't decorate the used type erasure, which is done to keep type names minimal for better error messages in debug builds. |
 | `CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE` | Enables support for experimental coroutines and `co_await` expressions. See \ref continuable_base::operator co_await() for details. |
 
 */

doc/index.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -70,13 +70,13 @@ your personal experience in using the library to improve it.
 \note If you are using the library in your open-source or commercial project
       I would highly appreciate if you could give me a short notice so I can
       add you to a list of projects and companies using this library.
-           
+
 \section mainpage-license License
 
 Continuable is licensed under the MIT license:
 
 >
->   Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+>   Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 >
 >   Permission is hereby granted, free of charge, to any person obtaining a copy
 >   of this software and associated documentation files(the "Software"), to deal
@@ -90,7 +90,7 @@ Continuable is licensed under the MIT license:
 >
 >   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 >   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
->   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+>   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 >   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 >   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 >   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

doc/installation.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -44,12 +44,12 @@ versions might work.
 \section installation-dependencies Dependencies
 
 Continuable is a header-only library with one required header-only dependency:
-  
+
   - [Naios/function2](https://github.com/Naios/function2) is used as type
     erasure wrapper to convert a \ref continuable_base into a \ref continuable.
 
 Additionally GTest is required as optional dependency for the asynchronous
-unit testing macros defined in `continuable/continuable-testing.hpp`
+unit testing macros defined in `continuable/support/gtest.hpp`
 if those are used:
 
   - [google/googletest](https://github.com/google/googletest) is used as
@@ -120,6 +120,14 @@ and might be installed from there.
            to make it available from various package managers in order to
            make the installation easier.
 
+\subsection installation-installation-amalgamation By using the amalgamation header
+
+For major versions there is an amalgamation header provided which can be
+included without any dependency:
+
+- [4.0.0](https://gist.githubusercontent.com/Naios/25d731aa4707d35a9bcec507f3cb9038/raw/051d2ea07b6704893c7fc9844e8d1c105c6821e0/continuable.hpp)
+- [3.0.0](https://gist.githubusercontent.com/Naios/b128ab5028a7eb33e4285c0293573d9f/raw/79fe332964a786b21a8661ef65d07a5669260a3c/continuable.hpp)
+
 \subsection installation-installation-copy By copying the headers
 
 If you don't want to rely on CMake or package managers it is possible to

doc/tutorial-awaiting-continuables.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -96,16 +96,34 @@ result.get_value();
 result.get_exception();
 \endcode
 
+\section tutorial-awaiting-continuables-return Using continuables as return type from coroutines
+
+It is possible to use a \ref continuable_base as return type from coroutines.
 
-\note It isn't possible as of now to use a \ref continuable_base
-      as return type from coroutines:
 \code{.cpp}
-cti::continuable<int> do_sth() {
+cti::continuable<> resolve_async_void() {
+  co_await http_request("github.com");
+  // ...
+  co_return;
+}
+
+cti::continuable<int> resolve_async() {
   co_await http_request("github.com");
   // ...
   co_return 0;
 }
 \endcode
 
+Additionally it's possible to return multiple return values from coroutines
+by wrapping those in a tuple like type:
+
+\code{.cpp}
+cti::continuable<int, int, int> resolve_async_multiple() {
+  co_await http_request("github.com");
+  // ...
+  co_return std::make_tuple(0, 1, 2);
+}
+\endcode
+
 */
 }

doc/tutorial-chaining-continuables.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

doc/tutorial-connecting-continuables.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -201,8 +201,8 @@ for (int i = 2; i < 5; ++i) {
   // to the container afterwards
   container.emplace_back(cti::make_ready_continuable(i));
 }
-                       
+
-cti::when_all(v)
+cti::when_all(std::move(v))
   .then([](std::vector<int> resolved) {
     // ...
   });

doc/tutorial-creating-continuables.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

doc/tutorial-promisify-continuables.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -50,7 +50,7 @@ The default callback style is something like
 Continuable offers the \ref promisify::from method for such callback styles.
 
 See an example of how to promisify boost asio's `async_resolve` below:
-  
+
 \code{.cpp}
 auto async_resolve(std::string host, std::string service) {
   return cti::promisify<asio::ip::udp::resolver::iterator>::from(
@@ -70,5 +70,30 @@ async_resolve("127.0.0.1", "daytime")
   });
 \endcode
 
+
+\section tutorial-promisify-continuables-boost-ct asio and boost::asio async completion tokens
+
+Since version 4.0.0 continuable also supports asio async initiation tokens.
+
+- Boost 1.70 or asio 1.13.0 is required for the async initiation
+- Until boost 1.72 or asio 1.16.0 overhead through an additional type
+  erasure is added. It is recommended to update to those versions.
+
+The special static variable \ref cti::use_continuable can be appended to any
+(boost) asio function that accepts a callback to make it return a \ref continuable_base.
+
+\code{.cpp}
+#include <continuable/continuable.hpp>
+#include <continuable/external/asio.hpp>
+#include <asio.hpp>
+
+// ...
+
+asio::tcp::resolver resolver(...);
+resolver.async_resolve("127.0.0.1", "daytime", cti::use_continuable)
+  .then([](asio::udp::resolver::iterator iterator) {
+    // ...
+  });
+\endcode
 */
 }

doc/tutorial-transforming-continuables.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -30,28 +30,37 @@ namespace cti {
 
 Sometimes it's required to change a \ref continuable_base object by its whole.
 Thus the library offers the ability to apply a transformation to any
-\ref continuable_base through using \link continuable_base::apply apply \endlink
+\ref continuable_base through using \link continuable_base::apply apply \endlink.
-or \link continuable_base::operator | its operator | \endlink.
 
-A transformation accepts a \ref continuable_base and returns
+A transformation is a callable object that accepts a \ref continuable_base
-an arbitrary object.
+and returns an arbitrary object
-
-To create a transformation use the \ref make_transform function:
-
-\code{.cpp}
-auto transform = cti::make_transform([] (auto&& continuable) {
-  // Change the continuable
-  return std::forward<decltype(continuable)>(continuable);
-});
-\endcode
 
 The library provides several transforms already as part of the
 \ref cti::transforms namespace.
 
+\section tutorial-transforming-continuables-wait Synchronous wait
+
+The library is capable of converting every asynchronous control flow
+into a synchronous one through \ref transforms::wait, \ref transforms::wait_for
+and \ref transforms::wait_until.
+
+\code{.cpp}
+std::string response = http_request("github.com")
+  .apply(cti::transforms::wait());
+
+std::string response = http_request("github.com")
+  .apply(cti::transforms::wait_for(std::chrono::seconds(5)));
+
+std::string response = http_request("github.com")
+  .apply(cti::transforms::wait_until(...));
+\endcode
+
+The current thread will be blocked until the result has arrived
+
 \section tutorial-transforming-continuables-future Conversion into std::future
 
 The library is capable of converting (*futurizing*) every continuable into a
-fitting `std::future` through the \ref transforms::futurize transform:
+fitting `std::future` through the \ref transforms::to_future transform:
 
 \code{.cpp}
 std::future<std::string> future = http_request("github.com")
@@ -59,17 +68,17 @@ std::future<std::string> future = http_request("github.com")
     // Do sth...
     return http_request("travis-ci.org") || http_request("atom.io");
   })
-  .apply(cti::transforms::futurize());
+  .apply(cti::transforms::to_future());
 // ^^^^^^^^
 \endcode
 
 Multiple arguments which can't be handled by `std::future` itself are
-converted into `std::tuple`, see \ref transforms::futurize for details.
+converted into `std::tuple`, see \ref transforms::to_future for details.
 
 \code{.cpp}
 std::future<std::tuple<std::string, std::string>> future =
   (http_request("travis-ci.org") && http_request("atom.io"))
-    .apply(cti::transforms::futurize());
+    .apply(cti::transforms::to_future());
 \endcode
 */
 }

doc/tutorial.dox

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

examples/example-ai/example-ai.cpp

@@ -7,7 +7,7 @@
                     https://github.com/Naios/continuable
                                    v3.0.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

examples/example-asio/CMakeLists.txt

@@ -1,15 +1,28 @@
+add_library(asio-example-deps INTERFACE)
+
+target_include_directories(asio-example-deps
+  INTERFACE
+    ${CMAKE_CURRENT_LIST_DIR})
+
+target_link_libraries(asio-example-deps
+  INTERFACE
+    asio
+    continuable)
+
 add_executable(example-asio
     ${CMAKE_CURRENT_LIST_DIR}/example-asio.cpp)
 
-target_include_directories(example-asio
-  PRIVATE
-    ${CMAKE_CURRENT_LIST_DIR})
-
 target_link_libraries(example-asio
   PRIVATE
-    asio
+    asio-example-deps)
-    continuable)
 
 target_compile_definitions(example-asio
   PUBLIC
     -DCONTINUABLE_WITH_NO_EXCEPTIONS)
+
+add_executable(example-asio-integration
+    ${CMAKE_CURRENT_LIST_DIR}/example-asio-integration.cpp)
+
+target_link_libraries(example-asio-integration
+  PRIVATE
+    asio-example-deps)

examples/example-asio/example-asio-integration.cpp

@@ -0,0 +1,176 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.0.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#include <asio.hpp>
+
+#include <continuable/continuable.hpp>
+#include <continuable/external/asio.hpp>
+
+// Queries the NIST daytime service and prints the current date and time
+void daytime_service();
+
+// Checks that a timer async_wait returns successfully
+void successful_async_wait();
+
+// Checks that a cancelled timer async_wait fails with
+// `asio::error::operation_aborted` and is converted to a default constructed
+// cti::exception_t.
+void cancelled_async_wait();
+
+// Indicates fatal error due to an unexpected failure in the continuation chain.
+void unexpected_error(cti::exception_t);
+
+// Check that the failure was an aborted operation, as expected.
+void check_aborted_operation(cti::exception_t);
+
+// Use a strand as executor
+void using_strand();
+
+int main(int, char**) {
+  daytime_service();
+
+  successful_async_wait();
+  cancelled_async_wait();
+
+  using_strand();
+
+  return 0;
+}
+
+void daytime_service() {
+  using asio::ip::tcp;
+  asio::io_context ioc(1);
+  tcp::resolver resolver(ioc);
+  tcp::socket socket(ioc);
+  std::string buf;
+
+  resolver.async_resolve("time.nist.gov", "daytime", cti::use_continuable)
+      .then([&socket](tcp::resolver::results_type endpoints) {
+        return asio::async_connect(socket, endpoints, cti::use_continuable);
+      })
+      .then([&socket, &buf] {
+        return asio::async_read_until(socket, asio::dynamic_buffer(buf), '\n',
+                                      cti::use_continuable);
+      })
+      .then([&buf](std::size_t) {
+        puts("Continuation successfully got a daytime response:");
+        puts(buf.c_str());
+      })
+      .fail(&unexpected_error);
+
+  ioc.run();
+}
+
+void successful_async_wait() {
+  asio::io_context ioc(1);
+  asio::steady_timer t(ioc);
+
+  t.expires_after(std::chrono::seconds(1));
+
+  t.async_wait(cti::use_continuable)
+      .then([] {
+        puts("Continuation succeeded after 1s as expected!");
+      })
+      .fail(&unexpected_error);
+
+  ioc.run();
+}
+
+void cancelled_async_wait() {
+  asio::io_context ioc(1);
+  asio::steady_timer t(ioc);
+
+  t.expires_after(std::chrono::seconds(999));
+
+  t.async_wait(cti::use_continuable)
+      .then([] {
+        puts("This should never be called");
+        std::terminate();
+      })
+      .fail(&check_aborted_operation);
+
+  t.cancel_one();
+  ioc.run();
+}
+
+void unexpected_error(cti::exception_t e) {
+  if (!bool(e)) {
+    puts("Continuation failed with unexpected cancellation!");
+    std::terminate();
+  }
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+  try {
+    std::rethrow_exception(e);
+  } catch (std::exception const& ex) {
+    puts("Continuation failed with unexpected exception");
+    puts(ex.what());
+  } catch (...) {
+    // Rethrow the exception to the asynchronous unhandled exception handler
+    std::rethrow_exception(std::current_exception());
+  }
+#else
+  puts("Continuation failed with unexpected error");
+  puts(e.message().data());
+#endif
+  std::terminate();
+}
+
+void check_aborted_operation(cti::exception_t ex) {
+  if (bool(ex)) {
+    unexpected_error(ex);
+  } else {
+    puts("Continuation failed due to aborted async operation, as expected.");
+  }
+}
+
+template <typename T>
+auto through_post(T& postable) {
+  return [&postable](auto&& work) mutable {
+    asio::post(postable, std::forward<decltype(work)>(work));
+  };
+}
+
+void using_strand() {
+  asio::io_context ioc(1);
+  asio::io_context::strand strand(ioc);
+
+  asio::post(strand, cti::use_continuable).then([]() {
+    puts("Dispatched through initiation token");
+  });
+
+  cti::async_on(
+      []() mutable {
+        puts("Dispatched through executor");
+      },
+      through_post(strand));
+
+  ioc.run();
+}

examples/example-asio/example-asio.cpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.0.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -34,12 +34,30 @@
 #include <string>
 #include <system_error>
 
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#include <exception>
+#endif
+
 #include <asio.hpp>
 
 #include <continuable/continuable.hpp>
 
 using namespace std::chrono_literals;
 
+inline auto error_code_remapper() {
+  return [](auto&& promise, asio::error_code e, auto&&... args) {
+    if (e) {
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+      promise.set_exception(std::make_exception_ptr(e));
+#else
+      promise.set_exception(cti::exception_t(e.value(), e.category()));
+#endif
+    } else {
+      promise.set_value(std::forward<decltype(args)>(args)...);
+    }
+  };
+}
+
 struct functional_io_service {
   asio::io_context service_;
   asio::ip::udp::resolver resolver_;
@@ -49,7 +67,11 @@ struct functional_io_service {
 
   auto trough_post() noexcept {
     return [&](auto&& work) mutable {
-      asio::post(service_, std::forward<decltype(work)>(work));
+      asio::post(service_,
+                 [work = std::forward<decltype(work)>(work)]() mutable {
+                   std::move(work)();
+                   // .. or: work.set_value();
+                 });
     };
   }
 
@@ -61,7 +83,8 @@ struct functional_io_service {
   }
 
   auto async_resolve(std::string host, std::string service) {
-    return cti::promisify<asio::ip::udp::resolver::iterator>::from(
+    return cti::promisify<asio::ip::udp::resolver::iterator>::with(
+        error_code_remapper(),
         [&](auto&&... args) {
           resolver_.async_resolve(std::forward<decltype(args)>(args)...);
         },
@@ -89,7 +112,7 @@ int main(int, char**) {
         // auto socket = std::make_shared<udp::socket>(service);
         // socket->async_send_to()
       })
-      .fail([](cti::error_type /*error*/) {
+      .fail([](cti::exception_t /*error*/) {
         // ...
       });
 

examples/example-slideshow/example-slideshow.cpp

@@ -1,5 +1,5 @@
 /*
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -13,7 +13,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

include/continuable/continuable-base.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -32,64 +32,30 @@
 #define CONTINUABLE_BASE_HPP_INCLUDED
 
 #include <cassert>
-#include <cstdint>
+#include <cstddef>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/continuable-primitives.hpp>
-#include <continuable/detail/base.hpp>
+#include <continuable/continuable-result.hpp>
-#include <continuable/detail/connection-all.hpp>
+#include <continuable/detail/connection/connection-all.hpp>
-#include <continuable/detail/connection-any.hpp>
+#include <continuable/detail/connection/connection-any.hpp>
-#include <continuable/detail/connection-seq.hpp>
+#include <continuable/detail/connection/connection-seq.hpp>
-#include <continuable/detail/connection.hpp>
+#include <continuable/detail/connection/connection.hpp>
+#include <continuable/detail/core/base.hpp>
+#include <continuable/detail/core/types.hpp>
 #include <continuable/detail/features.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/types.hpp>
+#include <continuable/detail/utility/util.hpp>
-#include <continuable/detail/util.hpp>
 
-#ifdef CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
+#if defined(CONTINUABLE_HAS_COROUTINE)
-#include <continuable/detail/awaiting.hpp>
+#  include <continuable/detail/other/coroutines.hpp>
-#endif // CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
+#endif // defined(CONTINUABLE_HAS_COROUTINE)
 
 namespace cti {
 /// \defgroup Base Base
 /// provides classes and functions to create continuable_base objects.
 /// \{
 
-/// Represents a tag which can be placed first in a signature
-/// in order to overload callables with the asynchronous result
-/// as well as an error.
-///
-/// See the example below:
-/// ```cpp
-/// struct my_callable {
-///   void operator() (std::string result) {
-///     // ...
-///   }
-///   void operator() (cti::dispatch_error_tag, cti::error_type) {
-///     // ...
-///   }
-/// };
-///
-/// // Will receive errors and results
-/// continuable.next(my_callable{});
-/// ```
-///
-/// \note see continuable::next for details.
-///
-/// \since 2.0.0
-using dispatch_error_tag = detail::types::dispatch_error_tag;
-
-/// Represents the type that is used as error type
-///
-/// By default this type deduces to `std::exception_ptr`.
-/// If `CONTINUABLE_WITH_NO_EXCEPTIONS` is defined the type
-/// will be a `std::error_condition`.
-/// A custom error type may be set through
-/// defining `CONTINUABLE_WITH_CUSTOM_ERROR_TYPE`.
-///
-/// \since 2.0.0
-using error_type = detail::types::error_type;
-
 /// Deduces to a true_type if the given type is a continuable_base.
 ///
 /// \since 3.0.0
@@ -126,6 +92,10 @@ template <typename Data, typename Annotation>
 class continuable_base {
 
   /// \cond false
+  using ownership = detail::util::ownership;
+
+  using annotation_trait = detail::annotation_trait<Annotation>;
+
   template <typename, typename>
   friend class continuable_base;
   friend struct detail::base::attorney;
@@ -133,25 +103,41 @@ class continuable_base {
   // The continuation type or intermediate result
   Data data_;
   // The transferable state which represents the validity of the object
-  detail::util::ownership ownership_;
+  ownership ownership_;
   /// \endcond
 
   /// Constructor accepting the data object while erasing the annotation
-  explicit continuable_base(Data data, detail::util::ownership ownership)
+  explicit continuable_base(Data data, ownership ownership)
-      : data_(std::move(data)), ownership_(std::move(ownership)) {
+    : data_(std::move(data))
-  }
+    , ownership_(std::move(ownership)) {}
 
 public:
   /// Constructor accepting the data object while erasing the annotation
-  explicit continuable_base(Data data) : data_(std::move(data)) {
+  explicit continuable_base(Data data)
-  }
+    : data_(std::move(data)) {}
 
   /// Constructor accepting any object convertible to the data object,
   /// while erasing the annotation
-  template <typename OData, std::enable_if_t<std::is_convertible<
+  template <typename OtherData,
-                                std::decay_t<OData>, Data>::value>* = nullptr>
+            std::enable_if_t<detail::base::can_accept_continuation<
-  continuable_base(OData&& data) : data_(std::forward<OData>(data)) {
+                Data, Annotation,
-  }
+                detail::traits::unrefcv_t<OtherData>>::value>* = nullptr>
+  /* implicit */ continuable_base(OtherData&& data)
+    : data_(
+          detail::base::proxy_continuable<Annotation,
+                                          detail::traits::unrefcv_t<OtherData>>(
+              std::forward<OtherData>(data))) {}
+
+  /// Constructor taking the data of other continuable_base objects
+  /// while erasing the hint.
+  ///
+  /// This constructor makes it possible to replace the internal data object of
+  /// the continuable by any object which is useful for type-erasure.
+  template <typename OData,
+            std::enable_if_t<std::is_convertible<
+                detail::traits::unrefcv_t<OData>, Data>::value>* = nullptr>
+  /* implicit */ continuable_base(continuable_base<OData, Annotation>&& other)
+    : data_(std::move(other).consume()) {}
 
   /// Constructor taking the data of other continuable_base objects
   /// while erasing the hint.
@@ -159,9 +145,8 @@ public:
   /// This constructor makes it possible to replace the internal data object of
   /// the continuable by any object which is useful for type-erasure.
   template <typename OData, typename OAnnotation>
-  continuable_base(continuable_base<OData, OAnnotation>&& other)
+  /* implicit */ continuable_base(continuable_base<OData, OAnnotation>&& other)
-      : continuable_base(std::move(other).materialize().consume_data()) {
+    : continuable_base(std::move(other).finish().consume()) {}
-  }
 
   /// \cond false
   continuable_base(continuable_base&&) = default;
@@ -240,12 +225,17 @@ public:
   /// | `Arg`                      | `continuable_base with <Arg>`             |
   /// | `std::pair<First, Second>` | `continuable_base with <First, Second>`   |
   /// | `std::tuple<Args...>`      | `continuable_base with <Args...>`         |
+  /// | `cti::result<Args...>`     | `continuable_base with <Args...>`         |
   /// | `continuable_base<Arg...>` | `continuable_base with <Args...>`         |
   ///          Which means the result type of the continuable_base is equal to
   ///          the plain types the callback returns (`std::tuple` and
   ///          `std::pair` arguments are unwrapped).
   ///          A single continuable_base as argument is resolved and the result
   ///          type is equal to the resolved continuable_base.
+  ///          A cti::result can be used to cancel the continuation or to
+  ///          transition to the exception handler.
+  ///          The special unwrapping of types can be disabled through wrapping
+  ///          such objects through a call to cti::make_plain.
   ///          Consider the following examples:
   /// ```cpp
   /// http_request("github.com")
@@ -267,6 +257,17 @@ public:
   /// http_request("github.com")
   ///   .then([](std::string github) { return http_request("atom.io"); })
   ///   .then([](std::string atom) { }); // <std::string>
+  ///
+  /// http_request("example.com")
+  ///   .then([](std::string content) -> result<std::string> {
+  ///     return rethrow(std::make_exception_ptr(std::exception{}));
+  ///   })
+  ///   .fail([] -> result<std::string> {
+  ///     return recover("Hello World!");
+  ///   })
+  ///   .then([](std::string content) -> result<std::string> {
+  ///     return cancel();
+  ///   })
   /// ```
   ///
   /// \since 1.0.0
@@ -275,7 +276,7 @@ public:
             E&& executor = detail::types::this_thread_executor_tag{}) && {
     return detail::base::chain_continuation<detail::base::handle_results::yes,
                                             detail::base::handle_errors::no>(
-        std::move(*this).materialize(), std::forward<T>(callback),
+        std::move(*this).finish(), std::forward<T>(callback),
         std::forward<E>(executor));
   }
 
@@ -301,7 +302,7 @@ public:
   template <typename OData, typename OAnnotation>
   auto then(continuable_base<OData, OAnnotation>&& continuation) && {
     return std::move(*this).then(
-        detail::base::wrap_continuation(std::move(continuation).materialize()));
+        detail::base::wrap_continuation(std::move(continuation).finish()));
   }
 
   /// Main method of the continuable_base to catch exceptions and error codes
@@ -316,12 +317,18 @@ public:
   /// ```cpp
   /// http_request("github.com")
   ///   .then([](std::string github) { })
-  ///   .fail([](std::exception_ptr ptr) {
+  ///   .fail([](std::exception_ptr ep) {
-  ///     // Handle the error here
+  ///     // Check whether the exception_ptr is valid (not default constructed)
-  ///     try {
+  ///     // if bool(ep) == false this means that the operation was cancelled
-  ///       std::rethrow_exception(ptr);
+  ///     // by the user or application (promise.set_canceled() or
-  ///     } catch (std::exception& e) {
+  ///     // make_cancelling_continuable()).
-  ///       e.what(); // Handle the exception
+  ///     if (ep) {
+  ///       // Handle the error here
+  ///       try {
+  ///         std::rethrow_exception(ep);
+  ///       } catch (std::exception& e) {
+  ///         e.what(); // Handle the exception
+  ///       }
   ///     }
   ///   });
   /// ```
@@ -341,14 +348,26 @@ public:
   /// \returns Returns a continuable_base with an asynchronous return type
   ///          depending on the previous result type.
   ///
+  /// \attention The given exception type exception_t can be passed to the
+  ///            handler in a default constructed state <br>`bool(e) == false`.
+  ///            This always means that the operation was cancelled by the user,
+  ///            possibly through:
+  ///              - \ref promise_base::set_canceled
+  ///              - \ref make_cancelling_continuable
+  ///              - \ref result::set_canceled
+  ///              - \ref cancel<br>
+  ///            In that case the exception can be ignored safely (but it is
+  ///            recommended not to proceed, although it is possible to
+  ///            recover from the cancellation).
   ///
   /// \since 2.0.0
   template <typename T, typename E = detail::types::this_thread_executor_tag>
   auto fail(T&& callback,
             E&& executor = detail::types::this_thread_executor_tag{}) && {
-    return detail::base::chain_continuation<detail::base::handle_results::no,
+    return detail::base::chain_continuation<
-                                            detail::base::handle_errors::plain>(
+        detail::base::handle_results::no, detail::base::handle_errors::forward>(
-        std::move(*this).materialize(), std::forward<T>(callback),
+        std::move(*this).finish(),
+        detail::base::strip_exception_arg(std::forward<T>(callback)),
         std::forward<E>(executor));
   }
 
@@ -370,9 +389,11 @@ public:
   /// \since 2.0.0
   template <typename OData, typename OAnnotation>
   auto fail(continuable_base<OData, OAnnotation>&& continuation) && {
-    continuation.freeze();
+    return std::move(*this)                                     //
-    return std::move(*this).fail([continuation = std::move(continuation)](
+        .fail([continuation = std::move(continuation).freeze()] //
-        error_type) mutable { std::move(continuation).done(); });
+              (exception_t) mutable {
+                std::move(continuation).done(); //
+              });
   }
 
   /// A method which allows to use an overloaded callable for the error
@@ -386,7 +407,7 @@ public:
   ///   void operator() (std::string result) {
   ///     // ...
   ///   }
-  ///   void operator() (cti::dispatch_error_tag, cti::error_type) {
+  ///   void operator() (cti::exception_arg_t, cti::exception_t) {
   ///     // ...
   ///   }
   ///
@@ -407,22 +428,56 @@ public:
             E&& executor = detail::types::this_thread_executor_tag{}) && {
     return detail::base::chain_continuation<
         detail::base::handle_results::yes,
-        detail::base::handle_errors::forward>(std::move(*this).materialize(),
+        detail::base::handle_errors::forward>(std::move(*this).finish(),
                                               std::forward<T>(callback),
                                               std::forward<E>(executor));
   }
 
-  /// A method which allows to apply this continuable to the given callable.
+  /// Returns a continuable_base which continues its invocation through the
+  /// given executor.
   ///
-  /// \param transform A transform which shall accept this continuable
+  /// \returns Returns a continuable_base of the same type.
+  ///
+  /// \since 4.2.0
+  template <typename E>
+  auto via(E&& executor) && {
+    return std::move(*this).next(
+        [](auto&&... args) {
+          return make_result(std::forward<decltype(args)>(args)...);
+        },
+        std::forward<E>(executor));
+  }
+
+  /// Returns a continuable_base which will have its signature converted
+  /// to the given Args.
+  ///
+  /// A signature can only be converted if it can be partially applied
+  /// from the previous one as shown below:
+  /// ```cpp
+  /// continuable<long> c = make_ready_continuable(0, 1, 2).as<long>();
+  /// ```
+  ///
+  /// \returns Returns a continuable_base with an asynchronous return type
+  ///          matching the given Args.
+  ///
+  /// \since 4.0.0
+  template <typename... Args>
+  auto as() && {
+    return std::move(*this).then(detail::base::convert_to<Args...>{});
+  }
+
+  /// A method which allows to apply a callable object to this continuable.
+  ///
+  /// \param transform A callable objects that transforms a continuable
+  ///                  to a different object.
   ///
   /// \returns Returns the result of the given transform when this
   ///          continuable is passed into it.
   ///
-  /// \since 2.0.0
+  /// \since 4.0.0
   template <typename T>
   auto apply(T&& transform) && {
-    return std::forward<T>(transform)(std::move(*this).materialize());
+    return std::forward<T>(transform)(std::move(*this).finish());
   }
 
   /// The pipe operator | is an alias for the continuable::then method.
@@ -438,22 +493,6 @@ public:
     return std::move(*this).then(std::forward<T>(right));
   }
 
-  /// The pipe operator | is an alias for the continuable::apply method.
-  ///
-  /// \param transform The transformer which is applied.
-  ///
-  /// \returns See the corresponding continuable_base::apply method for the
-  ///          explanation of the return type.
-  ///
-  /// \note    You may create your own transformation through
-  ///          calling make_transformation.
-  ///
-  /// \since 3.0.0
-  template <typename T>
-  auto operator|(detail::types::transform<T> transform) && {
-    return std::move(*this).apply(std::move(transform));
-  }
-
   /// Invokes both continuable_base objects parallel and calls the
   /// callback with the result of both continuable_base objects.
   ///
@@ -572,7 +611,64 @@ public:
   ///
   /// \since 1.0.0
   void done() && {
-    detail::base::finalize_continuation(std::move(*this));
+    detail::base::finalize_continuation(std::move(*this).finish());
+  }
+
+  /// Materializes the continuation expression template and finishes
+  /// the current applied strategy such that the resulting continuable
+  /// will always be a concrete type and Continuable::is_concrete holds.
+  ///
+  /// This can be used in the case where we are chaining continuations lazily
+  /// through a strategy, for instance when applying operators for
+  /// expressing connections and then want to return a materialized
+  /// continuable_base which uses the strategy respectively.
+  /// ```cpp
+  /// auto do_both() {
+  ///   return (wait(10s) || wait_key_pressed(KEY_SPACE)).finish();
+  /// }
+  ///
+  /// // Without a call to finish() this would lead to
+  /// // an unintended evaluation strategy:
+  /// do_both() || wait(5s);
+  /// ```
+  ///
+  /// \note When using a type erased continuable_base such as
+  ///       `continuable<...>` this method doesn't need to be called
+  ///       since the continuable_base is materialized automatically
+  ///       on conversion.
+  ///
+  /// \since 4.0.0
+  auto finish() && {
+    return annotation_trait::finish(std::move(*this));
+  }
+
+  /// Returns true when the continuable can provide its result immediately,
+  /// and its lazy invocation would be side-effect free.
+  ///
+  /// \since 4.0.0
+  bool is_ready() const noexcept {
+    return annotation_trait::is_ready(*this);
+  }
+
+  /// Invalidates the continuable and returns its immediate invocation result.
+  ///
+  /// This method can be used to specialize the asynchronous control flow
+  /// based on whether the continuable_base is_ready at every time,
+  /// which is true for a continuable created through the following functions:
+  ///   - make_ready_continuable
+  ///   - make_exceptional_continuable
+  ///
+  /// \returns   A result<Args...> where Args... represent the current
+  ///            asynchronous parameters or the currently stored exception.
+  ///
+  /// \attention unpack requires that continuable_base::is_ready returned true
+  ///            in a previous check, otherwise its behaviour is unspecified.
+  ///
+  /// \since 4.0.0
+  auto unpack() && {
+    assert(ownership_.is_acquired());
+    assert(is_ready());
+    return detail::base::attorney::query(std::move(*this).finish());
   }
 
   /// Predicate to check whether the cti::continuable_base is frozen or not.
@@ -618,7 +714,7 @@ public:
   }
 
   /// \cond false
-#ifdef CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
+#if defined(CONTINUABLE_HAS_COROUTINE)
   /// \endcond
   /// Implements the operator for awaiting on continuables using `co_await`.
   ///
@@ -644,49 +740,47 @@ public:
   /// ```
   ///
   /// In case the library is configured to use error codes or a custom
-  /// error type the return type of the co_await expression is changed.
+  /// exception type the return type of the co_await expression is changed.
-  /// The result is returned through an internal proxy object which may
+  /// The result is returned through a cti::result<...>.
-  /// be queried for the error object.
   /// |          Continuation type        |          co_await returns          |
   /// | : ------------------------------- | : -------------------------------- |
-  /// | `continuable_base with <>`        | `unspecified<void>`                |
+  /// | `continuable_base with <>`        | `result<void>`                     |
-  /// | `continuable_base with <Arg>`     | `unspecified<Arg>`                 |
+  /// | `continuable_base with <Arg>`     | `result<Arg>`                      |
-  /// | `continuable_base with <Args...>` | `unspecified<std::tuple<Args...>>` |
+  /// | `continuable_base with <Args...>` | `result<Args...>`                  |
-  /// The interface of the proxy object is similar to the one proposed in
+  ///
-  /// the `std::expected` proposal:
+  /// \note  Using continuable_base as return type for coroutines
+  ///        is supported. The coroutine is initially stopped and
+  ///        resumed when the continuation is requested in order to
+  ///        keep the lazy evaluation semantics of the continuable_base.
   /// ```cpp
-  /// if (auto&& result = co_await http_request("github.com")) {
+  /// cti::continuable<> resolve_async_void() {
-  ///   auto value = *result;
+  ///   co_await http_request("github.com");
-  /// } else {
+  ///   // ...
-  ///   cti::error_type error = result.get_exception();
+  ///   co_return;
   /// }
   ///
-  /// auto result = co_await http_request("github.com");
+  /// cti::continuable<int> resolve_async() {
-  /// bool(result);
-  /// result.is_value();
-  /// result.is_exception();
-  /// *result; // Same as result.get_value()
-  /// result.get_value();
-  /// result.get_exception();
-  /// ```
-  ///
-  /// \attention Note that it isn't possible as of now to use a continuable
-  ///            as return type from coroutines as depicted below:
-  /// ```cpp
-  /// cti::continuable<int> do_sth() {
   ///   co_await http_request("github.com");
   ///   // ...
   ///   co_return 0;
   /// }
   /// ```
-  ///            Propably this will be added in a future version of the library.
+  /// It's possible to return multiple return values from coroutines
+  /// by wrapping those in a tuple like type:
+  /// ```cpp
+  /// cti::continuable<int, int, int> resolve_async_multiple() {
+  ///   co_await http_request("github.com");
+  ///   // ...
+  ///   co_return std::make_tuple(0, 1, 2);
+  /// }
+  /// ```
   ///
   /// \since     2.0.0
   auto operator co_await() && {
-    return detail::awaiting::create_awaiter(std::move(*this).materialize());
+    return detail::awaiting::create_awaiter(std::move(*this).finish());
   }
   /// \cond false
-#endif // CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
+#endif // defined(CONTINUABLE_HAS_COROUTINE)
   /// \endcond
 
 private:
@@ -694,12 +788,7 @@ private:
     ownership_.release();
   }
 
-  auto materialize() && {
+  Data&& consume() && {
-    return detail::connection::materializer<continuable_base>::apply(
-        std::move(*this));
-  }
-
-  Data&& consume_data() && {
     assert_acquired();
     release();
     return std::move(data_);
@@ -803,9 +892,9 @@ constexpr auto make_continuable(Continuation&& continuation) {
                 "use make_continuable<void>(...). Continuables with an exact "
                 "signature may be created through make_continuable<Args...>.");
 
-  return detail::base::attorney::create(
+  return detail::base::attorney::create_from(
       std::forward<Continuation>(continuation),
-      detail::hints::extract(detail::traits::identity<Args...>{}),
+      typename detail::hints::from_args<Args...>::type{},
       detail::util::ownership{});
 }
 
@@ -815,46 +904,18 @@ constexpr auto make_continuable(Continuation&& continuation) {
 /// \attention Usually using this function isn't needed at all since
 ///            the continuable library is capable of working with
 ///            plain values in most cases.
-///            Try not to use it since it causes unneccessary recursive
+///            Try not to use it since it causes unnecessary recursive
 ///            function calls.
 ///
 /// \since     3.0.0
 template <typename... Args>
-constexpr auto make_ready_continuable() {
+auto make_ready_continuable(Args&&... args) {
-  return make_continuable<void>([](auto&& promise) {
+  return detail::base::attorney::create_from_raw(
-    std::forward<decltype(promise)>(promise).set_value();
+      detail::base::ready_continuation<detail::traits::unrefcv_t<Args>...>(
-  });
+          result<detail::traits::unrefcv_t<Args>...>::from(
-}
+              std::forward<Args>(args)...)),
-
+      detail::identity<detail::traits::unrefcv_t<Args>...>{},
-/// Returns a continuable_base with one result value which instantly resolves
+      detail::util::ownership{});
-/// the promise with the given value.
-///
-/// \copydetails make_ready_continuable()
-template <typename Result>
-constexpr auto make_ready_continuable(Result&& result) {
-  return make_continuable<std::decay_t<Result>>( // ...
-      [result = std::forward<Result>(result)](auto&& promise) mutable {
-        std::forward<decltype(promise)>(promise).set_value(std::move(result));
-      });
-}
-
-/// Returns a continuable_base with multiple result values which instantly
-/// resolves the promise with the given values.
-///
-/// \copydetails make_ready_continuable()
-template <typename FirstResult, typename SecondResult, typename... Rest>
-constexpr auto make_ready_continuable(FirstResult&& first_result,
-                                      SecondResult&& second_result,
-                                      Rest&&... rest) {
-  return make_continuable<std::decay_t<FirstResult>, std::decay_t<SecondResult>,
-                          std::decay_t<Rest>...>( // ...
-      [result = std::make_tuple(std::forward<FirstResult>(first_result),
-                                std::forward<SecondResult>(second_result),
-                                std::forward<Rest>(rest)...)](
-          auto&& promise) mutable {
-        detail::traits::unpack(result,
-                               std::forward<decltype(promise)>(promise));
-      });
 }
 
 /// Returns a continuable_base with the parameterized result which instantly
@@ -867,20 +928,213 @@ constexpr auto make_ready_continuable(FirstResult&& first_result,
 /// auto ct = cti::make_exceptional_continuable<int>(ptr);
 /// ```
 ///
-/// \tparam Signature The fake signature of the returned continuable.
+/// \tparam Args The fake signature of the returned continuable.
 ///
 /// \since            3.0.0
-template <typename... Signature, typename Exception>
+template <typename... Args, typename Exception>
 constexpr auto make_exceptional_continuable(Exception&& exception) {
+  static_assert(sizeof...(Args) > 0,
+                "Requires at least one type for the fake signature!");
+
+  using hint_t = typename detail::hints::from_args<Args...>::type;
+  using ready_continuation_t = typename detail::base::
+      ready_continuation_from_hint<hint_t>::type;
+  using result_t = typename detail::base::result_from_hint<hint_t>::type;
+  return detail::base::attorney::create_from_raw(
+      ready_continuation_t(result_t::from(exception_arg_t{},
+                                          std::forward<Exception>(exception))),
+      hint_t{}, detail::util::ownership{});
+}
+
+/// Returns a continuable_base with the parameterized result which never
+/// resolves its promise and thus cancels the asynchronous continuation chain
+/// through throwing a default constructed exception_t.
+///
+/// This can be used to cancel an asynchronous continuation chain when
+/// returning a continuable_base from a handler where other paths could
+/// possibly continue the asynchronous chain. See an example below:
+/// ```cpp
+/// do_sth().then([weak = this->weak_from_this()]() -> continuable<> {
+///   if (auto me = weak.lock()) {
+///     return do_sth_more();
+///   } else {
+///     // Abort the asynchronous continuation chain since the
+///     // weakly referenced object expired previously.
+///     return make_cancelling_continuable<void>();
+///   }
+/// });
+/// ```
+/// The default unhandled exception handler ignores exception types
+/// that don't evaluate to true when being converted to a bool.
+/// This saves expensive construction of std::exception_ptr or similar types,
+/// where only one exception type is used for signaling the cancellation.
+///
+/// \tparam Signature The fake signature of the returned continuable.
+///
+/// \since            4.0.0
+template <typename... Signature>
+auto make_cancelling_continuable() {
   static_assert(sizeof...(Signature) > 0,
                 "Requires at least one type for the fake signature!");
 
-  return make_continuable<Signature...>( // ...
+  return make_exceptional_continuable<Signature...>(exception_t{});
-      [exception = std::forward<Exception>(exception)](auto&& promise) mutable {
-        std::forward<decltype(promise)>(promise).set_exception(
-            std::move(exception));
-      });
 }
+
+/// Can be used to disable the special meaning for a returned value in
+/// asynchronous handler functions.
+///
+/// Several types have a special meaning when being returned from a callable
+/// passed to asynchronous handler functions like:
+/// - continuable_base::then
+/// - continuable_base::fail
+/// - continuable_base::next
+///
+/// For instance such types are std::tuple, std::pair and cti::result.
+///
+/// Wrapping such an object through a call to make_plain disables the special
+/// meaning for such objects as shown below:
+/// ```cpp
+/// continuable<result<int, int> c = http_request("example.com")
+///   .then([](std::string content) {
+///     return make_plain(make_result(0, 1));
+///   })
+/// ```
+///
+/// \since 4.0.0
+///
+template <typename T>
+auto make_plain(T&& value) {
+  return plain_t<detail::traits::unrefcv_t<T>>(std::forward<T>(value));
+}
+
+/// Can be used to recover to from a failure handler,
+/// the result handler which comes after will be called with the
+/// corresponding result.
+///
+/// The \ref exceptional_result returned by this function can be returned
+/// from any result or failure handler in order to rethrow the exception.
+/// ```cpp
+/// http_request("example.com")
+///   .then([](std::string content) {
+///     return recover(1, 2);
+///   })
+///   .fail([](cti::exception_t exception) {
+///     return recover(1, 2);
+///   })
+///   .then([](int a, int b) {
+///     // Recovered from the failure
+///   })
+/// ```
+/// A corresponding \ref result is returned by \ref recover
+/// ```cpp
+/// http_request("example.com")
+///   .then([](std::string content) -> cti::result<int, int> {
+///     return recover(1, 2);
+///   })
+///   .fail([](cti::exception_t exception) -> cti::result<int, int> {
+///     return recover(1, 2);
+///   })
+///   .then([](int a, int b) -> cti::result<int, int> {
+///     // Recovered from the failure
+///   })
+/// ```
+///
+/// \since 4.0.0
+///
+template <typename... Args>
+result<detail::traits::unrefcv_t<Args>...> recover(Args&&... args) {
+  return make_result(std::forward<Args>(args)...);
+}
+
+/// Can be used to rethrow an exception to the asynchronous continuation chain,
+/// the failure handler which comes after will be called with the
+/// corresponding exception.
+///
+/// The \ref exceptional_result returned by this function can be returned
+/// from any result or failure handler in order to rethrow the exception.
+/// ```cpp
+/// http_request("example.com")
+///   .then([](std::string content) {
+///     return rethrow(std::make_exception_ptr(std::exception{}));
+///   })
+///   .fail([](cti::exception_t exception) {
+///     return rethrow(std::make_exception_ptr(std::exception{}));
+///   })
+///   .next([](auto&&...) {
+///     return rethrow(std::make_exception_ptr(std::exception{}));
+///   });
+/// ```
+/// The returned \ref exceptional_result is convertible to
+/// any \ref result as shown below:
+/// ```cpp
+/// http_request("example.com")
+///   .then([](std::string content) -> cti::result<> {
+///     return rethrow(std::make_exception_ptr(std::exception{}));
+///   })
+///   .fail([](cti::exception_t exception) -> cti::result<> {
+///     return rethrow(std::make_exception_ptr(std::exception{}));
+///   })
+///   .next([](auto&&...) -> cti::result<> {
+///     return rethrow(std::make_exception_ptr(std::exception{}));
+///   });
+/// ```
+///
+/// \since 4.0.0
+///
+// NOLINTNEXTLINE(performance-unnecessary-value-param)
+inline exceptional_result rethrow(exception_t exception) {
+  // NOLINTNEXTLINE(hicpp-move-const-arg, performance-move-const-arg)
+  return exceptional_result{std::move(exception)};
+}
+
+/// Can be used to cancel an asynchronous continuation chain,
+/// the next failure handler which comes after cancel will be called
+/// with a default constructed exception_t object.
+///
+/// The \ref cancellation_result returned by this function can be returned from
+/// any result or failure handler in order to cancel the chain.
+/// ```cpp
+/// http_request("example.com")
+///   .then([](std::string content) {
+///     return cancel();
+///   })
+///   .fail([](cti::exception_t exception) {
+///     return cancel();
+///   })
+///   .next([](auto&&...) {
+///     return cancel();
+///   });
+/// ```
+/// The returned \ref empty_result is convertible to
+/// any \ref result as shown below:
+/// ```cpp
+/// http_request("example.com")
+///   .then([](std::string content) -> cti::result<> {
+///     return cancel();
+///   })
+///   .fail([](cti::exception_t exception) -> cti::result<> {
+///     return cancel();
+///   })
+///   .next([](auto&&...) -> cti::result<> {
+///     return cancel();
+///   });
+/// ```
+///
+/// \since 4.0.0
+///
+inline cancellation_result cancel() {
+  return {};
+}
+
+/// Can be used to stop an asynchronous continuation chain,
+/// no handler which comes after stop was received won't be called.
+///
+/// \since 4.0.0
+///
+inline empty_result stop() {
+  return {};
+}
+
 /// \}
 } // namespace cti
 

include/continuable/continuable-connections.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -35,12 +35,11 @@
 #include <memory>
 #include <utility>
 #include <vector>
-
+#include <continuable/detail/connection/connection-all.hpp>
-#include <continuable/detail/connection-all.hpp>
+#include <continuable/detail/connection/connection-any.hpp>
-#include <continuable/detail/connection-any.hpp>
+#include <continuable/detail/connection/connection-seq.hpp>
-#include <continuable/detail/connection-seq.hpp>
+#include <continuable/detail/connection/connection.hpp>
-#include <continuable/detail/connection.hpp>
+#include <continuable/detail/traversal/range.hpp>
-#include <continuable/detail/range.hpp>
 
 namespace cti {
 /// \defgroup Connections Connections

include/continuable/continuable-coroutine.hpp

@@ -0,0 +1,97 @@
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_COROUTINE_HPP_INCLUDED
+#define CONTINUABLE_COROUTINE_HPP_INCLUDED
+
+#include <continuable/continuable-base.hpp>
+#include <continuable/continuable-types.hpp>
+#include <continuable/detail/core/types.hpp>
+#include <continuable/detail/features.hpp>
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#  include <exception>
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+
+#if defined(CONTINUABLE_HAS_COROUTINE)
+#  include <continuable/detail/other/coroutines.hpp>
+
+namespace cti {
+#  if defined(CONTINUABLE_HAS_EXCEPTIONS)
+/// Is thrown from co_await expressions if the awaited continuable is canceled
+///
+/// Default constructed exception types that are returned by a cancelled
+/// continuable are converted automatically to await_canceled_exception when
+/// being returned by a co_await expression.
+///
+/// The await_canceled_exception gets converted again to a default constructed
+/// exception type if it becomes unhandled inside a coroutine which
+/// returns a continuable_base.
+/// ```cpp
+/// continuable<> cancelled_coroutine() {
+///   co_await make_cancelling_continuable<void>();
+///
+///   co_return;
+/// }
+///
+/// // ...
+///
+/// cancelled_coroutine().fail([](exception_t e) {
+///   assert(bool(e) == false);
+/// });
+/// ```
+///
+/// \since 4.1.0
+using await_canceled_exception = detail::awaiting::await_canceled_exception;
+#  endif // CONTINUABLE_HAS_EXCEPTIONS
+} // namespace cti
+
+/// \cond false
+// As far as I know there is no other way to implement this specialization...
+// NOLINTNEXTLINE(cert-dcl58-cpp)
+namespace std {
+#  if defined(CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE)
+namespace experimental {
+#  endif // defined(CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE)
+template <typename Data, typename... Args, typename... FunctionArgs>
+struct coroutine_traits<
+    cti::continuable_base<Data, cti::detail::identity<Args...>>,
+    FunctionArgs...> {
+
+  using promise_type = cti::detail::awaiting::promise_type<
+      cti::continuable<Args...>, cti::promise<Args...>, Args...>;
+};
+#  if defined(CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE)
+} // namespace experimental
+#  endif // defined(CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE)
+} // namespace std
+  /// \endcond
+#endif // defined(CONTINUABLE_HAS_COROUTINE)
+
+#endif // CONTINUABLE_COROUTINE_HPP_INCLUDED

include/continuable/continuable-operations.hpp

@@ -0,0 +1,41 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_OPERATIONS_HPP_INCLUDED
+#define CONTINUABLE_OPERATIONS_HPP_INCLUDED
+
+/// \defgroup Operations Operations
+/// provides functions to work with asynchronous control flows.
+
+#include <continuable/operations/async.hpp>
+#include <continuable/operations/loop.hpp>
+#include <continuable/operations/split.hpp>
+
+#endif // CONTINUABLE_OPERATIONS_HPP_INCLUDED

include/continuable/continuable-primitives.hpp

@@ -0,0 +1,141 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_PRIMITIVES_HPP_INCLUDED
+#define CONTINUABLE_PRIMITIVES_HPP_INCLUDED
+
+#include <continuable/detail/core/types.hpp>
+#include <continuable/detail/utility/identity.hpp>
+
+namespace cti {
+/// \defgroup Primitives Primitives
+/// provides basic tag types for creating a customized callbacks
+/// and continuations.
+///
+/// For the callback and the continuation `Args...` represents the
+/// asynchronous result:
+/// ```cpp
+/// template<typename... Args>
+/// struct continuation {
+///   void operator() (callback<Args...>);
+///   bool operator() (cti::is_ready_arg_t) const;
+///   result<Args...> operator() (cti::unpack_arg_t);
+/// };
+/// ```
+/// ```cpp
+/// template<typename... Args>
+/// struct callback {
+///   void operator() (Args...) &&;
+///   void operator() (cti::exception_arg_t, cti::exception_t) &&;
+/// };
+/// ```
+/// \{
+
+/// Represents the tag type that is used to specify the signature hint
+/// of a continuable_base or promise_base.
+///
+/// \since 4.0.0
+template <typename... Args>
+using signature_arg_t = detail::identity<Args...>;
+
+/// Represents the tag type that is used to query the continuation
+/// for whether it resolves the callback instantly with its arguments
+/// without having side effects.
+///
+/// \since 4.0.0
+struct is_ready_arg_t {};
+
+/// Represents the tag type that is used to unpack the result of a continuation.
+///
+/// \attention It's required that the query of is_ready_arg_t returns true,
+///            otherwise the behaviour when unpacking is unspecified.
+///
+/// \since 4.0.0
+struct unpack_arg_t {};
+
+/// \copydoc unpack_arg_t
+///
+/// \deprecated The query_arg_t was deprecated because of
+///             its new naming unpack_arg_t.
+///
+[[deprecated("The dispatch_error_tag was replaced by unpack_arg_t and will "
+             "be removed in a later major version!")]] //
+    typedef unpack_arg_t query_arg_t;
+
+/// Represents the tag type that is used to disambiguate the
+/// callback operator() in order to take the exception asynchronous chain.
+///
+/// \note see continuable::next for details.
+///
+/// \since 4.0.0
+struct exception_arg_t {};
+
+/// \copydoc exception_arg_t
+///
+/// \deprecated The dispatch_error_tag was deprecated in order to move closer
+///             to the types specified in the "A Unified Future" proposal
+///             especially regarding naming types similar.
+///
+[[deprecated("The dispatch_error_tag was replaced by exception_arg_t and will "
+             "be removed in a later major version!")]] //
+    typedef exception_arg_t dispatch_error_tag;
+
+/// Represents the type that is used as exception type
+///
+/// By default this type deduces to `std::exception_ptr`.
+/// If `CONTINUABLE_WITH_NO_EXCEPTIONS` is defined the type
+/// will be a `std::error_condition`.
+/// A custom error type may be set through
+/// defining `CONTINUABLE_WITH_CUSTOM_ERROR_TYPE`.
+///
+/// \since 4.0.0
+using exception_t = detail::types::exception_t;
+
+/// \copydoc exception_t
+///
+/// \deprecated The error_type was deprecated in order to move closer
+///             to the types specified in the "A Unified Future" proposal
+///             especially regarding naming types similar.
+///
+[[deprecated("The error_type was replaced by exception_t and will "
+             "be removed in a later major version!")]] //
+    typedef exception_t error_type;
+
+/// Represents the type that is used to disable the special meaning of types
+/// which are returned by a asynchronous result handler.
+/// See cti::plain for details.
+///
+/// \since 4.0.0
+template <typename T>
+using plain_t = detail::types::plain_tag<T>;
+/// \}
+} // namespace cti
+
+#endif // CONTINUABLE_PRIMITIVES_HPP_INCLUDED

include/continuable/continuable-promise-base.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -31,12 +31,14 @@
 #ifndef CONTINUABLE_PROMISE_BASE_HPP_INCLUDED
 #define CONTINUABLE_PROMISE_BASE_HPP_INCLUDED
 
+#include <cassert>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/continuable-primitives.hpp>
-#include <continuable/detail/hints.hpp>
+#include <continuable/detail/core/annotation.hpp>
-#include <continuable/detail/types.hpp>
+#include <continuable/detail/core/types.hpp>
-#include <continuable/detail/util.hpp>
+#include <continuable/detail/utility/traits.hpp>
+#include <continuable/detail/utility/util.hpp>
 
 namespace cti {
 /// \defgroup Base Base
@@ -51,7 +53,7 @@ namespace cti {
 ///
 /// If we want to resolve the  promise_base trough the call operator,
 /// and we want to resolve it through an exception, we must call it with a
-/// dispatch_error_tag as first and the exception as second argument.
+/// exception_arg_t as first and the exception as second argument.
 /// Additionally the promise is resolveable only through its call
 /// operator when invoked as an r-value.
 ///
@@ -62,7 +64,7 @@ class promise_base
   /// \cond false
   ;
 template <typename Data, typename... Args>
-class promise_base<Data, detail::hints::signature_hint_tag<Args...>>
+class promise_base<Data, detail::identity<Args...>>
     : detail::util::non_copyable
   /// \endcond
 { // clang-format on
@@ -73,51 +75,138 @@ class promise_base<Data, detail::hints::signature_hint_tag<Args...>>
   /// \endcond
 
 public:
+  /// Constructor for constructing an empty promise
+  explicit promise_base() = default;
   /// Constructor accepting the data object
   explicit promise_base(Data data) : data_(std::move(data)) {
   }
 
+  /// \cond false
+  promise_base(promise_base&&) = default;
+  promise_base(promise_base const&) = delete;
+
+  promise_base& operator=(promise_base&&) = default;
+  promise_base& operator=(promise_base const&) = delete;
+  /// \endcond
+
   /// Constructor accepting any object convertible to the data object
-  template <typename OData, std::enable_if_t<std::is_convertible<
+  template <typename OData,
-                                std::decay_t<OData>, Data>::value>* = nullptr>
+            std::enable_if_t<std::is_convertible<
-  promise_base(OData&& data) : data_(std::forward<OData>(data)) {
+                detail::traits::unrefcv_t<OData>, Data>::value>* = nullptr>
+  /* implicit */ promise_base(OData&& data) : data_(std::forward<OData>(data)) {
+  }
+
+  /// Assignment operator accepting any object convertible to the data object
+  template <typename OData,
+            std::enable_if_t<std::is_convertible<
+                detail::traits::unrefcv_t<OData>, Data>::value>* = nullptr>
+  promise_base& operator=(OData&& data) {
+    data_ = std::forward<OData>(data);
+    return *this;
   }
 
   /// Resolves the continuation with the given values.
   ///
   /// \throws This method never throws an exception.
   ///
+  /// \attention This method may only be called once,
+  ///            when the promise is valid operator bool() returns true.
+  ///            Calling this method will invalidate the promise such that
+  ///            subsequent calls to operator bool() will return false.
+  ///            This behaviour is only consistent in promise_base and
+  ///            non type erased promises may behave differently.
+  ///            Invoking an invalid promise_base is undefined!
+  ///
   /// \since  2.0.0
   void operator()(Args... args) && noexcept {
+    assert(data_);
     std::move(data_)(std::move(args)...);
+    data_ = nullptr;
   }
   /// Resolves the continuation with the given exception.
   ///
   /// \throws This method never throws an exception.
   ///
+  /// \attention This method may only be called once,
+  ///            when the promise is valid operator bool() returns true.
+  ///            Calling this method will invalidate the promise such that
+  ///            subsequent calls to operator bool() will return false.
+  ///            This behaviour is only consistent in promise_base and
+  ///            non type erased promises may behave differently.
+  ///            Invoking an invalid promise_base is undefined!
+  ///
   /// \since  2.0.0
-  void operator()(detail::types::dispatch_error_tag tag,
+  void operator()(exception_arg_t tag, exception_t exception) && noexcept {
-                  detail::types::error_type exception) &&
+    assert(data_);
-      noexcept {
     std::move(data_)(tag, std::move(exception));
+    data_ = nullptr;
   }
 
   /// Resolves the continuation with the given values.
   ///
   /// \throws This method never throws an exception.
   ///
+  /// \attention This method may only be called once,
+  ///            when the promise is valid operator bool() returns true.
+  ///            Calling this method will invalidate the promise such that
+  ///            subsequent calls to operator bool() will return false.
+  ///            This behaviour is only consistent in promise_base and
+  ///            non type erased promises may behave differently.
+  ///            Invoking an invalid promise_base is undefined!
+  ///
   /// \since  2.0.0
   void set_value(Args... args) noexcept {
+    // assert(data_);
     std::move(data_)(std::move(args)...);
+    data_ = nullptr;
   }
 
   /// Resolves the continuation with the given exception.
   ///
   /// \throws This method never throws an exception.
   ///
+  /// \attention This method may only be called once,
+  ///            when the promise is valid operator bool() returns true.
+  ///            Calling this method will invalidate the promise such that
+  ///            subsequent calls to operator bool() will return false.
+  ///            This behaviour is only consistent in promise_base and
+  ///            non type erased promises may behave differently.
+  ///            Invoking an invalid promise_base is undefined!
+  ///
   /// \since  2.0.0
-  void set_exception(detail::types::error_type exception) noexcept {
+  void set_exception(exception_t exception) noexcept {
-    std::move(data_)(detail::types::dispatch_error_tag{}, std::move(exception));
+    assert(data_);
+    std::move(data_)(exception_arg_t{}, std::move(exception));
+    data_ = nullptr;
+  }
+
+  /// Resolves the continuation with the cancellation token which is represented
+  /// by a default constructed exception_t.
+  ///
+  /// \throws This method never throws an exception.
+  ///
+  /// \attention This method may only be called once,
+  ///            when the promise is valid operator bool() returns true.
+  ///            Calling this method will invalidate the promise such that
+  ///            subsequent calls to operator bool() will return false.
+  ///            This behaviour is only consistent in promise_base and
+  ///            non type erased promises may behave differently.
+  ///            Invoking an invalid promise_base is undefined!
+  ///
+  /// \since  4.0.0
+  void set_canceled() noexcept {
+    assert(data_);
+    std::move(data_)(exception_arg_t{}, exception_t{});
+    data_ = nullptr;
+  }
+
+  /// Returns true if the continuation is valid (non empty).
+  ///
+  /// \throws This method never throws an exception.
+  ///
+  /// \since  4.0.0
+  explicit operator bool() const noexcept {
+    return bool(data_);
   }
 };
 /// \}

include/continuable/continuable-promisify.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -33,8 +33,7 @@
 
 #include <type_traits>
 #include <utility>
-
+#include <continuable/detail/other/promisify.hpp>
-#include <continuable/detail/promisify.hpp>
 
 namespace cti {
 /// \defgroup Promisify Promisify
@@ -72,18 +71,47 @@ public:
   /// }
   /// ```
   ///
-  /// If the error code which is passed as first parameter is set there are
+  /// A given error variable is converted to the used error type.
-  /// two behaviours depending whether exceptions are enabled:
+  /// If this isn't possible you need to create a custom resolver callable
-  /// - If exceptions are enabled the error type is passed via
+  /// object \see with for details.
-  ///   an exception_ptr to the failure handler.
-  /// - If exceptions are disabled the error type is converted to a
-  ///   `std::error_conditon` and passed down to the error handler.
   ///
   /// \since  3.0.0
   template <typename Callable, typename... Args>
   static auto from(Callable&& callable, Args&&... args) {
-    return helper::template from<detail::convert::promisify_default>(
+    return helper::template from(detail::convert::default_resolver(),
-        std::forward<Callable>(callable), std::forward<Args>(args)...);
+                                 std::forward<Callable>(callable),
+                                 std::forward<Args>(args)...);
+  }
+
+  /// \copybrief from
+  ///
+  /// This modification of \ref from additionally takes a resolver callable
+  /// object which is used to resolve the promise from the given result.
+  ///
+  /// See an example of how to promisify boost asio's async_resolve below:
+  /// ```cpp
+  /// auto async_resolve(std::string host, std::string service) {
+  ///   return cti::promisify<asio::ip::udp::resolver::iterator>::with(
+  ///       [](auto&& promise, auto&& e, auto&&... args) {
+  ///         if (e) {
+  ///           promise.set_exception(std::forward<decltype(e)>(e));
+  ///         } else {
+  ///           promise.set_value(std::forward<decltype(args)>(args)...);
+  ///         }
+  ///       },
+  ///       [&](auto&&... args) {
+  ///         resolver_.async_resolve(std::forward<decltype(args)>(args)...);
+  ///       },
+  ///       std::move(host), std::move(service));
+  /// }
+  /// ```
+  ///
+  /// \since 4.0.0
+  template <typename Resolver, typename Callable, typename... Args>
+  static auto with(Resolver&& resolver, Callable&& callable, Args&&... args) {
+    return helper::template from(std::forward<Resolver>(resolver),
+                                 std::forward<Callable>(callable),
+                                 std::forward<Args>(args)...);
   }
 };
 /// \}

include/continuable/continuable-result.hpp

@@ -0,0 +1,356 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_RESULT_HPP_INCLUDED
+#define CONTINUABLE_RESULT_HPP_INCLUDED
+
+#include <type_traits>
+#include <utility>
+#include <continuable/continuable-primitives.hpp>
+#include <continuable/detail/utility/result-trait.hpp>
+#include <continuable/detail/utility/result-variant.hpp>
+#include <continuable/detail/utility/traits.hpp>
+#include <continuable/detail/utility/util.hpp>
+
+namespace cti {
+/// \defgroup Result Result
+/// provides the \ref result class and corresponding utility functions to work
+/// with the result of an asynchronous operation which can possibly yield:
+/// - *no result*: If the operation didn't finish
+/// - *a value*: If the operation finished successfully
+/// - *an exception*: If the operation finished with an exception
+///                   or was cancelled.
+/// \{
+
+/// A tag which represents present void values in result.
+///
+/// \since 4.0.0
+using void_arg_t = detail::void_arg_t;
+
+/// A class which is convertible to any \ref result and that definitely holds no
+/// value so the real result gets invalidated when this object is passed to it.
+///
+/// \since 4.0.0
+///
+struct empty_result {};
+
+/// A class which is convertible to any \ref result and that definitely holds
+/// a default constructed exception which signals the cancellation of the
+/// asynchronous control flow.
+///
+/// \since 4.0.0
+///
+struct cancellation_result {};
+
+/// A class which is convertible to any result and that holds
+/// an exception which is then passed to the converted result object.
+///
+/// \since 4.0.0
+///
+class exceptional_result {
+  exception_t exception_;
+
+public:
+  exceptional_result() = delete;
+  exceptional_result(exceptional_result const&) = default;
+  exceptional_result(exceptional_result&&) = default;
+  exceptional_result& operator=(exceptional_result const&) = default;
+  exceptional_result& operator=(exceptional_result&&) = default;
+  ~exceptional_result() = default;
+
+  explicit exceptional_result(exception_t exception)
+    // NOLINTNEXTLINE(hicpp-move-const-arg, performance-move-const-arg)
+    : exception_(std::move(exception)) {}
+
+  exceptional_result& operator=(exception_t exception) {
+    // NOLINTNEXTLINE(hicpp-move-const-arg, performance-move-const-arg)
+    exception_ = std::move(exception);
+    return *this;
+  }
+
+  /// Sets an exception
+  void set_exception(exception_t exception) {
+    // NOLINTNEXTLINE(hicpp-move-const-arg, performance-move-const-arg)
+    exception_ = std::move(exception);
+  }
+
+  /// Returns the contained exception
+  exception_t& get_exception() & noexcept {
+    return exception_;
+  }
+  /// \copydoc get_exception
+  exception_t const& get_exception() const& noexcept {
+    return exception_;
+  }
+  /// \copydoc get_exception
+  exception_t&& get_exception() && noexcept {
+    return std::move(exception_);
+  }
+};
+
+/// The result class can carry the three kinds of results an asynchronous
+/// operation possibly can return, it's implemented in a variant like
+/// data structure which is also specialized to hold arbitrary arguments.
+///
+/// The result can be in the following three states:
+/// - *no result*: If the operation didn't finish
+/// - *a value*: If the operation finished successfully
+/// - *an exception*: If the operation finished with an exception
+///                   or was cancelled.
+///
+/// The interface of the result object is similar to the one proposed in
+/// the `std::expected` proposal:
+/// ```cpp
+/// result<std::string> result = make_result("Hello World!");
+/// bool(result);
+/// result.is_value();
+/// result.is_exception();
+/// *result; // Same as result.get_value()
+/// result.get_value();
+/// result.get_exception();
+/// ```
+///
+/// \since 4.0.0
+///
+template <typename... T>
+class result {
+  using trait_t = detail::result_trait<T...>;
+
+  template <typename... Args>
+  explicit result(detail::init_result_arg_t arg, Args&&... values)
+    : variant_(arg, trait_t::wrap(std::forward<Args>(values)...)) {}
+  explicit result(detail::init_exception_arg_t arg, exception_t exception)
+    : variant_(arg, std::move(exception)) {}
+
+public:
+  using value_t = typename trait_t::value_t;
+  using value_placeholder_t = typename trait_t::surrogate_t;
+
+  template <typename FirstArg, typename... Args>
+  explicit result(FirstArg&& first, Args&&... values)
+    : variant_(detail::init_result_arg_t{},
+               trait_t::wrap(std::forward<FirstArg>(first),
+                             std::forward<Args>(values)...)) {}
+
+  result() = default;
+  result(result const&) = delete;
+  result(result&&) = default;
+  result& operator=(result const&) = delete;
+  result& operator=(result&&) = default;
+  ~result() = default;
+
+  explicit result(exception_t exception)
+    : variant_(detail::init_exception_arg_t{}, std::move(exception)) {}
+  /* implicit */ result(empty_result) {}
+  /* implicit */ result(exceptional_result exceptional_result)
+    : variant_(detail::init_exception_arg_t{},
+               std::move(exceptional_result.get_exception())) {}
+  /* implicit */ result(cancellation_result)
+    : variant_(detail::init_exception_arg_t{}, exception_t{}) {}
+
+  result& operator=(empty_result) {
+    variant_.set_empty();
+    return *this;
+  }
+  result& operator=(value_placeholder_t value) {
+    variant_.set_value(std::move(value));
+    return *this;
+  }
+  result& operator=(exceptional_result exception) {
+    variant_.set_exception(std::move(exception.get_exception()));
+    return *this;
+  }
+  result& operator=(cancellation_result) {
+    variant_.set_exception({});
+    return *this;
+  }
+
+  /// Set the result to an empty state
+  void set_empty() {
+    variant_.set_empty();
+  }
+  /// Set the result to a the state which holds the corresponding value
+  void set_value(T... values) {
+    variant_.set_value(trait_t::wrap(std::move(values)...));
+  }
+  /// Set the result into a state which holds the corresponding exception
+  void set_exception(exception_t exception) {
+    variant_.set_exception(std::move(exception));
+  }
+  /// Set the result into a state which holds the cancellation token
+  void set_canceled() {
+    variant_.set_exception(exception_t{});
+  }
+
+  /// Returns true if the state of the result is empty
+  bool is_empty() const noexcept {
+    return variant_.is_empty();
+  }
+  /// Returns true if the state of the result holds the result
+  bool is_value() const noexcept {
+    return variant_.is_value();
+  }
+  /// Returns true if the state of the result holds a present exception
+  bool is_exception() const noexcept {
+    return variant_.is_exception();
+  }
+
+  /// \copydoc is_value
+  explicit constexpr operator bool() const noexcept {
+    return is_value();
+  }
+
+  /// Returns the values of the result, if the result doesn't hold the value
+  /// the behaviour is undefined but will assert in debug mode.
+  decltype(auto) get_value() & noexcept {
+    return trait_t::unwrap(variant_.get_value());
+  }
+  ///\copydoc get_value
+  decltype(auto) get_value() const& noexcept {
+    return trait_t::unwrap(variant_.get_value());
+  }
+  ///\copydoc get_value
+  decltype(auto) get_value() && noexcept {
+    return trait_t::unwrap(std::move(variant_.get_value()));
+  }
+
+  ///\copydoc get_value
+  decltype(auto) operator*() & noexcept {
+    return get_value();
+  }
+  ///\copydoc get_value
+  decltype(auto) operator*() const& noexcept {
+    return get_value();
+  }
+  ///\copydoc get_value
+  decltype(auto) operator*() && noexcept {
+    return std::move(variant_.get_value());
+  }
+
+  /// Returns the exception of the result, if the result doesn't hold an
+  /// exception the behaviour is undefined but will assert in debug mode.
+  exception_t& get_exception() & noexcept {
+    return variant_.get_exception();
+  }
+  /// \copydoc get_exception
+  exception_t const& get_exception() const& noexcept {
+    return variant_.get_exception();
+  }
+  /// \copydoc get_exception
+  exception_t&& get_exception() && noexcept {
+    return std::move(variant_.get_exception());
+  }
+
+  /// Creates a present result from the given values
+  static result from(T... values) {
+    return result{detail::init_result_arg_t{}, std::move(values)...};
+  }
+  /// Creates a present result from the given exception
+  static result from(exception_arg_t, exception_t exception) {
+    return result{detail::init_exception_arg_t{}, std::move(exception)};
+  }
+
+  /// Creates an empty result
+  static result empty() {
+    return result{empty_result{}};
+  }
+
+private:
+  detail::result_variant<value_placeholder_t> variant_;
+};
+
+/// Returns the value at position I of the given result
+template <std::size_t I, typename... T>
+decltype(auto) get(result<T...>& result) {
+  return detail::result_trait<T...>::template get<I>(result);
+}
+/// \copydoc get
+template <std::size_t I, typename... T>
+decltype(auto) get(result<T...> const& result) {
+  return detail::result_trait<T...>::template get<I>(result);
+}
+/// \copydoc get
+template <std::size_t I, typename... T>
+decltype(auto) get(result<T...>&& result) {
+  return detail::result_trait<T...>::template get<I>(std::move(result));
+}
+
+/// Creates a present result from the given values.
+///
+/// This could be used to pass the result of the next handler to the same
+/// asynchronous path it came from as shown below:
+/// ```cpp
+/// make_ready_continuable().next([&](auto&&... args) {
+///   result<> captured = make_result(std::forward<decltype(args)>(args)...);
+///   return shutdown().then([captured = std::move(captured)]() mutable {
+///     return std::move(captured);
+///   });
+/// });
+/// ```
+///
+/// \since 4.0.0
+template <typename... T,
+          typename Result = result<detail::traits::unrefcv_t<T>...>>
+Result make_result(T&&... values) {
+  return Result::from(std::forward<T>(values)...);
+}
+
+/// Creates an exceptional_result from the given exception.
+///
+/// \copydetails make_result
+///
+/// \since 4.0.0
+inline exceptional_result make_result(exception_arg_t, exception_t exception) {
+  // NOLINTNEXTLINE(hicpp-move-const-arg, performance-move-const-arg)
+  return exceptional_result{std::move(exception)};
+}
+/// \}
+} // namespace cti
+
+namespace std {
+// The GCC standard library defines tuple_size as class and struct which
+// triggers a warning here.
+#if defined(__clang__)
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wmismatched-tags"
+#endif
+template <typename... Args>
+struct tuple_size<cti::result<Args...>>
+  : std::integral_constant<size_t, sizeof...(Args)> {};
+
+template <std::size_t I, typename... Args>
+struct tuple_element<I, cti::result<Args...>>
+  : tuple_element<I, tuple<Args...>> {};
+#if defined(__clang__)
+#  pragma GCC diagnostic pop
+#endif
+} // namespace std
+
+#endif // CONTINUABLE_RESULT_HPP_INCLUDED

include/continuable/continuable-trait.hpp

@@ -1,80 +0,0 @@
-
-/*
-
-                        /~` _  _ _|_. _     _ |_ | _
-                        \_,(_)| | | || ||_|(_||_)|(/_
-
-                    https://github.com/Naios/continuable
-                                   v3.0.0
-
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
-
-  Permission is hereby granted, free of charge, to any person obtaining a copy
-  of this software and associated documentation files(the "Software"), to deal
-  in the Software without restriction, including without limitation the rights
-  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
-  copies of the Software, and to permit persons to whom the Software is
-  furnished to do so, subject to the following conditions :
-
-  The above copyright notice and this permission notice shall be included in
-  all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
-  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-  SOFTWARE.
-**/
-
-#ifndef CONTINUABLE_TRAIT_HPP_INCLUDED
-#define CONTINUABLE_TRAIT_HPP_INCLUDED
-
-#include <cstdint>
-
-#include <continuable/continuable-base.hpp>
-#include <continuable/continuable-promise-base.hpp>
-#include <continuable/detail/hints.hpp>
-#include <continuable/detail/types.hpp>
-
-namespace cti {
-/// \defgroup Types Types
-/// provides the \link cti::continuable continuable\endlink and \link
-/// cti::promise promise\endlink facility for type erasure.
-/// \{
-
-/// Trait to retrieve a continuable_base type with a given type-erasure backend.
-///
-/// Every object may me used as type-erasure backend as long as the
-/// requirements of a `std::function` like wrapper are satisfied.
-///
-/// \tparam CallbackWrapper The type which is used to erase the callback.
-///
-/// \tparam ContinuationWrapper The type which is used to erase the
-///         continuation data.
-///
-/// \tparam Args The current signature of the continuable.
-template <template <std::size_t, typename...> class CallbackWrapper,
-          template <std::size_t, typename...> class ContinuationWrapper,
-          typename... Args>
-class continuable_trait {
-
-  using callback = CallbackWrapper<0U, void(Args...)&&,
-                                   void(detail::types::dispatch_error_tag,
-                                        detail::types::error_type) &&>;
-
-public:
-  /// The promise type which is used to resolve continuations
-  using promise =
-      promise_base<callback, detail::hints::signature_hint_tag<Args...>>;
-
-  /// The continuable type for the given parameters.
-  using continuable =
-      continuable_base<ContinuationWrapper<sizeof(callback), void(promise)>,
-                       detail::hints::signature_hint_tag<Args...>>;
-};
-/// \}
-} // namespace cti
-
-#endif // CONTINUABLE_TRAIT_HPP_INCLUDED

include/continuable/continuable-transforms.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -31,8 +31,8 @@
 #ifndef CONTINUABLE_TRANSFORMS_HPP_INCLUDED
 #define CONTINUABLE_TRANSFORMS_HPP_INCLUDED
 
-#include <continuable/detail/transforms.hpp>
+#include <continuable/transforms/wait.hpp>
-#include <continuable/detail/types.hpp>
+#include <continuable/transforms/future.hpp>
 
 namespace cti {
 /// \defgroup Transforms Transforms
@@ -41,70 +41,12 @@ namespace cti {
 /// types such as (`std::future`).
 /// \{
 
-/// A callable tag object which marks a wrapped callable object
-/// as continuable transformation which enables some useful overloads.
-///
-/// \since 3.0.0
-template <typename T>
-using transform = detail::types::transform<T>;
-
-/// Wraps the given callable object into a transform class.
-///
-/// \since 3.0.0
-template <typename T>
-auto make_transform(T&& callable) {
-  return transform<std::decay_t<T>>(std::forward<T>(callable));
-}
-
 /// The namespace transforms declares callable objects that transform
 /// any continuable_base to an object or to a continuable_base itself.
 ///
 /// Transforms can be applied to continuables through using
 /// the cti::continuable_base::apply method accordingly.
-namespace transforms {
+namespace transforms {}
-/// Returns a transform that if applied to a continuable,
-/// it will start the continuation chain and returns the asynchronous
-/// result as `std::future<...>`.
-///
-/// \returns Returns a `std::future<...>` which becomes ready as soon
-///          as the the continuation chain has finished.
-///          The signature of the future depends on the result type:
-/// |          Continuation type        |             Return type            |
-/// | : ------------------------------- | : -------------------------------- |
-/// | `continuable_base with <>`        | `std::future<void>`                |
-/// | `continuable_base with <Arg>`     | `std::future<Arg>`                 |
-/// | `continuable_base with <Args...>` | `std::future<std::tuple<Args...>>` |
-///
-/// \attention If exceptions are used, exceptions that are thrown, are forwarded
-///            to the returned future. If there are no exceptions supported,
-///            you shall not pass any errors to the end of the asynchronous
-///            call chain!
-///            Otherwise this will yield a trap that causes application exit.
-///
-/// \since 2.0.0
-inline auto futurize() {
-  return make_transform([](auto&& continuable) {
-    using detail::transforms::as_future;
-    return as_future(std::forward<decltype(continuable)>(continuable));
-  });
-}
-
-/// Returns a transform that if applied to a continuable, it will ignores all
-/// error which ocured until the point the transform was applied.
-///
-/// \returns Returns a continuable with the same signature as applied to.
-///
-/// \attention This can be used to create a continuable which doesn't resolve
-///            the continuation on errors.
-///
-/// \since 2.0.0
-inline auto flatten() {
-  return make_transform([](auto&& continuable) {
-    return std::forward<decltype(continuable)>(continuable).fail([](auto&&) {});
-  });
-}
-/// \}
-} // namespace transforms
 } // namespace cti
 
 #endif // CONTINUABLE_TRANSFORMS_HPP_INCLUDED

include/continuable/continuable-traverse-async.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -32,8 +32,7 @@
 #define CONTINUABLE_TRAVERSE_ASYNC_HPP_INCLUDED
 
 #include <utility>
-
+#include <continuable/detail/traversal/traverse-async.hpp>
-#include <continuable/detail/traverse-async.hpp>
 
 namespace cti {
 /// \defgroup Traversal Traversal
@@ -75,7 +74,7 @@ using async_traverse_in_place_tag =
 ///    ```cpp
 ///    struct my_async_visitor {
 ///      /// The synchronous overload is called for each object,
-///      /// it may return false to suspend the current control.
+///      /// it may return false to suspend the current control flow.
 ///      /// In that case the overload below is called.
 ///      template <typename T>
 ///      bool operator()(async_traverse_visit_tag, T&& element) {

include/continuable/continuable-traverse.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -34,8 +34,7 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/detail/traversal/traverse.hpp>
-#include <continuable/detail/traverse.hpp>
 
 namespace cti {
 /// \defgroup Traversal Traversal

include/continuable/continuable-types.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -31,11 +31,11 @@
 #ifndef CONTINUABLE_TYPES_HPP_INCLUDED
 #define CONTINUABLE_TYPES_HPP_INCLUDED
 
-#include <cstdint>
-
 #include <function2/function2.hpp>
-
+#include <continuable/continuable-base.hpp>
-#include <continuable/continuable-trait.hpp>
+#include <continuable/continuable-primitives.hpp>
+#include <continuable/continuable-promise-base.hpp>
+#include <continuable/detail/other/erasure.hpp>
 
 namespace cti {
 /// \defgroup Types Types
@@ -43,48 +43,59 @@ namespace cti {
 /// cti::promise promise\endlink facility for type erasure.
 /// \{
 
-// clang-format off
+/// Deduces to the preferred continuation capacity for a possible
-namespace detail {
+/// small functor optimization. The given capacity size is always enough to
-/// A function which isn't size adjusted and move only
+/// to avoid any allocation when storing a ready continuable_base.
-template<std::size_t, typename... Args>
+///
-using unique_function_adapter = fu2::unique_function<Args...>;
+/// \since 4.0.0
-/// A function which is size adjusted and move only
+template <typename... Args>
-template<std::size_t Size, typename... Args>
+using continuation_capacity = detail::erasure::continuation_capacity<Args...>;
-using unique_function_adjustable = fu2::function_base<true, false, Size,
-                                                      true, false, Args...>;
-
-/// We adjust the internal capacity of the outer function wrapper so
-/// we don't have to allocate twice when using `continuable<...>`.
-template<typename... Args>
-using unique_trait_of = continuable_trait<
-  unique_function_adapter,
-  unique_function_adjustable,
-  Args...
->;
-} // namespace detail
 
 /// Defines a non-copyable continuation type which uses the
 /// function2 backend for type erasure.
 ///
 /// Usable like: `continuable<int, float>`
+///
+/// \note You can always define your own continuable with a type erasure of
+///       choice, the type erasure wrapper just needs to accept a
+///       callable object with a continuation signature as specified
+///       in the Primitives section.
+///
+/// \since 1.0.0
 template <typename... Args>
-using continuable = typename detail::unique_trait_of<
+using continuable = continuable_base<detail::erasure::continuation<Args...>, //
-  Args...
+                                     signature_arg_t<Args...>>;
->::continuable;
 
 /// Defines a non-copyable promise type which is using the
 /// function2 backend for type erasure.
 ///
 /// Usable like: `promise<int, float>`
+///
+/// \note You can always define your own promise with a type erasure of
+///       choice, the type erasure wrapper just needs to accept a
+///       callable object with a callback signature as specified
+///       in the Primitives section.
+///
+/// \since 1.0.0
 template <typename... Args>
-using promise = typename detail::unique_trait_of<
+using promise = promise_base<detail::erasure::callback<Args...>, //
-  Args...
+                             signature_arg_t<Args...>>;
->::promise;
 
-// TODO channel
+/// Defines a non-copyable type erasure which is capable of carrying
-// TODO sink
+/// callable objects passed to executors.
-
+///
-// clang-format on
+/// The work behaves like a `promise<>` but the work type erasure uses extra
+/// stack space for small object optimization.
+/// Additionally the outstanding work can be resolved through an exception.
+///
+/// \note You can always define your own cancelable_work with a type erasure of
+///       choice, the type erasure wrapper just needs to accept a
+///       callable object which is callable with a `void()` and
+///       `void(exception_arg_t, exception_t)` signature.
+///
+/// \since 4.0.0
+using work = promise_base<detail::erasure::work, //
+                          signature_arg_t<>>;
 /// \}
 } // namespace cti
 

include/continuable/continuable.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -47,9 +47,12 @@ namespace cti {}
 
 #include <continuable/continuable-base.hpp>
 #include <continuable/continuable-connections.hpp>
+#include <continuable/continuable-coroutine.hpp>
+#include <continuable/continuable-operations.hpp>
+#include <continuable/continuable-primitives.hpp>
 #include <continuable/continuable-promise-base.hpp>
 #include <continuable/continuable-promisify.hpp>
-#include <continuable/continuable-trait.hpp>
+#include <continuable/continuable-result.hpp>
 #include <continuable/continuable-transforms.hpp>
 #include <continuable/continuable-traverse-async.hpp>
 #include <continuable/continuable-traverse.hpp>

include/continuable/detail/awaiting.hpp

@@ -1,144 +0,0 @@
-
-/*
-
-                        /~` _  _ _|_. _     _ |_ | _
-                        \_,(_)| | | || ||_|(_||_)|(/_
-
-                    https://github.com/Naios/continuable
-                                   v3.0.0
-
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
-
-  Permission is hereby granted, free of charge, to any person obtaining a copy
-  of this software and associated documentation files(the "Software"), to deal
-  in the Software without restriction, including without limitation the rights
-  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
-  copies of the Software, and to permit persons to whom the Software is
-  furnished to do so, subject to the following conditions :
-
-  The above copyright notice and this permission notice shall be included in
-  all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
-  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-  SOFTWARE.
-**/
-
-// Exclude this header when coroutines are not available
-#ifndef CONTINUABLE_DETAIL_AWAITING_HPP_INCLUDED
-#define CONTINUABLE_DETAIL_AWAITING_HPP_INCLUDED
-
-#include <cassert>
-#include <experimental/coroutine>
-
-#include <continuable/detail/expected.hpp>
-#include <continuable/detail/features.hpp>
-#include <continuable/detail/hints.hpp>
-#include <continuable/detail/types.hpp>
-#include <continuable/detail/util.hpp>
-
-#if defined(CONTINUABLE_HAS_EXCEPTIONS)
-#include <exception>
-#endif // CONTINUABLE_HAS_EXCEPTIONS
-
-namespace cti {
-namespace detail {
-namespace awaiting {
-/// We import the coroutine handle in our namespace
-using std::experimental::coroutine_handle;
-
-/// An object which provides the internal buffer and helper methods
-/// for waiting on a continuable in a stackless coroutine.
-template <typename Continuable>
-class awaitable {
-  using trait_t = container::expected_result_trait_t<Continuable>;
-
-  /// The continuable which is invoked upon suspension
-  Continuable continuable_;
-  /// A cache which is used to pass the result of the continuation
-  /// to the coroutine.
-  typename trait_t::expected_type result_;
-
-public:
-  explicit constexpr awaitable(Continuable&& continuable)
-      : continuable_(std::move(continuable)) {
-  }
-
-  /// Since continuables are evaluated lazily we are not
-  /// capable to say whether the resumption will be instantly.
-  bool await_ready() const noexcept {
-    return false;
-  }
-
-  /// Suspend the current context
-  // TODO Convert this to an r-value function once possible
-  void await_suspend(coroutine_handle<> h) {
-    // Forward every result to the current awaitable
-    std::move(continuable_)
-        .next([h, this](auto&&... args) mutable {
-          resolve(std::forward<decltype(args)>(args)...);
-          h.resume();
-        })
-        .done();
-  }
-
-  /// Resume the coroutine represented by the handle
-  auto await_resume() noexcept(false) {
-    if (result_) {
-      // When the result was resolved return it
-      return trait_t::unwrap(std::move(result_));
-    }
-
-#if defined(CONTINUABLE_HAS_EXCEPTIONS)
-    std::rethrow_exception(result_.get_exception());
-#else  // CONTINUABLE_HAS_EXCEPTIONS
-    // Returning error types in await isn't supported as of now
-    util::trap();
-#endif // CONTINUABLE_HAS_EXCEPTIONS
-  }
-
-private:
-  /// Resolve the continuation through the result
-  template <typename... Args>
-  void resolve(Args&&... args) {
-    result_.set_value(trait_t::wrap(std::forward<Args>(args)...));
-  }
-
-  /// Resolve the continuation through an error
-  void resolve(types::dispatch_error_tag, types::error_type error) {
-    result_.set_exception(std::move(error));
-  }
-};
-
-/// Converts a continuable into an awaitable object as described by
-/// the C++ coroutine TS.
-template <typename T>
-constexpr auto create_awaiter(T&& continuable) {
-  return awaitable<std::decay_t<T>>(std::forward<T>(continuable));
-}
-} // namespace awaiting
-} // namespace detail
-} // namespace cti
-
-// As far as I know there is no other was to implement this specialization...
-// NOLINTNEXTLINE(cert-dcl58-cpp)
-namespace std {
-namespace experimental {
-template <typename Data, typename... Args, typename... FunctionArgs>
-struct coroutine_traits<
-    cti::continuable_base<Data,
-                          cti::detail::hints::signature_hint_tag<Args...>>,
-    FunctionArgs...> {
-
-  static_assert(cti::detail::traits::fail<Data>::value,
-                "Using a continuable as return type from co_return "
-                "expressions isn't supported yet!");
-};
-} // namespace experimental
-} // namespace std
-
-#endif // CONTINUABLE_DETAIL_UTIL_HPP_INCLUDED

include/continuable/detail/base.hpp

@@ -1,593 +0,0 @@
-
-/*
-
-                        /~` _  _ _|_. _     _ |_ | _
-                        \_,(_)| | | || ||_|(_||_)|(/_
-
-                    https://github.com/Naios/continuable
-                                   v3.0.0
-
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
-
-  Permission is hereby granted, free of charge, to any person obtaining a copy
-  of this software and associated documentation files(the "Software"), to deal
-  in the Software without restriction, including without limitation the rights
-  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
-  copies of the Software, and to permit persons to whom the Software is
-  furnished to do so, subject to the following conditions :
-
-  The above copyright notice and this permission notice shall be included in
-  all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
-  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-  SOFTWARE.
-**/
-
-#ifndef CONTINUABLE_DETAIL_BASE_HPP_INCLUDED
-#define CONTINUABLE_DETAIL_BASE_HPP_INCLUDED
-
-#include <tuple>
-#include <type_traits>
-#include <utility>
-
-#include <continuable/detail/features.hpp>
-#include <continuable/detail/hints.hpp>
-#include <continuable/detail/traits.hpp>
-#include <continuable/detail/types.hpp>
-#include <continuable/detail/util.hpp>
-
-#if defined(CONTINUABLE_HAS_EXCEPTIONS)
-#include <exception>
-#endif // CONTINUABLE_HAS_EXCEPTIONS
-
-namespace cti {
-namespace detail {
-/// The namespace `base` provides the low level API for working
-/// with continuable types.
-///
-/// Important methods are:
-/// - Creating a continuation from a callback taking functional
-///   base::attorney::create(auto&& callback)
-///     -> base::continuation<auto>
-/// - Chaining a continuation together with a callback
-///   base::chain_continuation(base::continuation<auto> continuation,
-///                            auto&& callback)
-///     -> base::continuation<auto>
-/// - Finally invoking the continuation chain
-///    base::finalize_continuation(base::continuation<auto> continuation)
-///     -> void
-namespace base {
-template <typename T>
-struct is_continuable : std::false_type {};
-template <typename Data, typename Annotation>
-struct is_continuable<continuable_base<Data, Annotation>> : std::true_type {};
-
-/// Helper class to access private methods and members of
-/// the continuable_base class.
-struct attorney {
-  /// Makes a continuation wrapper from the given argument
-  template <typename T, typename A>
-  static auto create(T&& continuation, A /*hint*/, util::ownership ownership_) {
-    return continuable_base<std::decay_t<T>, std::decay_t<A>>(
-        std::forward<T>(continuation), ownership_);
-  }
-
-  /// Invokes a continuation object in a reference correct way
-  template <typename Data, typename Annotation, typename Callback>
-  static auto
-  invoke_continuation(continuable_base<Data, Annotation>&& continuation,
-                      Callback&& callback) noexcept {
-    auto materialized = std::move(continuation).materialize();
-    materialized.release();
-    return materialized.data_(std::forward<Callback>(callback));
-  }
-
-  template <typename Data, typename Annotation>
-  static auto materialize(continuable_base<Data, Annotation>&& continuation) {
-    return std::move(continuation).materialize();
-  }
-
-  template <typename Data, typename Annotation>
-  static Data&&
-  consume_data(continuable_base<Data, Annotation>&& continuation) {
-    return std::move(continuation).consume_data();
-  }
-
-  template <typename Continuable>
-  static util::ownership ownership_of(Continuable&& continuation) noexcept {
-    return continuation.ownership_;
-  }
-};
-
-// Returns the invoker of a callback, the next callback
-// and the arguments of the previous continuation.
-//
-// The return type of the invokerOf function matches a callable of:
-//   void(auto&& callback, auto&& next_callback, auto&&... args)
-//
-// The invoker decorates the result type in the following way
-// - void              -> next_callback()
-// - ?                 -> next_callback(?)
-// - std::pair<?, ?>   -> next_callback(?, ?)
-// - std::tuple<?...>  -> next_callback(?...)
-//
-// When the result is a continuation itself pass the callback to it
-// - continuation<?...> -> result(next_callback);
-namespace decoration {
-/// Helper class wrapping the underlaying unwrapping lambda
-/// in order to extend it with a hint method.
-template <typename T, typename Hint>
-class invoker : public T {
-public:
-  constexpr explicit invoker(T invoke) : T(std::move(invoke)) {
-  }
-
-  using T::operator();
-
-  /// Returns the underlaying signature hint
-  static constexpr Hint hint() noexcept {
-    return {};
-  }
-};
-
-#if defined(CONTINUABLE_HAS_EXCEPTIONS)
-#define CONTINUABLE_BLOCK_TRY_BEGIN try {
-#define CONTINUABLE_BLOCK_TRY_END                                              \
-  }                                                                            \
-  catch (...) {                                                                \
-    std::forward<decltype(next_callback)>(next_callback)(                      \
-        types::dispatch_error_tag{}, std::current_exception());                \
-  }
-
-#else // CONTINUABLE_HAS_EXCEPTIONS
-#define CONTINUABLE_BLOCK_TRY_BEGIN {
-#define CONTINUABLE_BLOCK_TRY_END }
-#endif // CONTINUABLE_HAS_EXCEPTIONS
-
-/// Invokes the given callable object with the given arguments while
-/// marking the operation as non exceptional.
-template <typename T, typename... Args>
-constexpr auto invoke_no_except(T&& callable, Args&&... args) noexcept {
-  return std::forward<T>(callable)(std::forward<Args>(args)...);
-}
-
-template <typename T, typename... Args>
-constexpr auto make_invoker(T&& invoke, hints::signature_hint_tag<Args...>) {
-  return invoker<std::decay_t<T>, hints::signature_hint_tag<Args...>>(
-      std::forward<T>(invoke));
-}
-
-/// - continuable<?...> -> result(next_callback);
-template <typename Data, typename Annotation>
-constexpr auto
-invoker_of(traits::identity<continuable_base<Data, Annotation>>) {
-  /// Get the hint of the unwrapped returned continuable
-  using Type = decltype(attorney::materialize(
-      std::declval<continuable_base<Data, Annotation>>()));
-
-  auto constexpr const hint = hints::hint_of(traits::identify<Type>{});
-
-  return make_invoker(
-      [](auto&& callback, auto&& next_callback, auto&&... args) {
-        CONTINUABLE_BLOCK_TRY_BEGIN
-          auto continuation_ =
-              util::partial_invoke(std::forward<decltype(callback)>(callback),
-                                   std::forward<decltype(args)>(args)...);
-
-          attorney::invoke_continuation(
-              std::move(continuation_),
-              std::forward<decltype(next_callback)>(next_callback));
-        CONTINUABLE_BLOCK_TRY_END
-      },
-      hint);
-}
-
-/// - ? -> next_callback(?)
-template <typename T>
-constexpr auto invoker_of(traits::identity<T>) {
-  return make_invoker(
-      [](auto&& callback, auto&& next_callback, auto&&... args) {
-        CONTINUABLE_BLOCK_TRY_BEGIN
-          auto result =
-              util::partial_invoke(std::forward<decltype(callback)>(callback),
-                                   std::forward<decltype(args)>(args)...);
-
-          invoke_no_except(std::forward<decltype(next_callback)>(next_callback),
-                           std::move(result));
-        CONTINUABLE_BLOCK_TRY_END
-      },
-      traits::identify<T>{});
-}
-
-/// - void -> next_callback()
-inline auto invoker_of(traits::identity<void>) {
-  return make_invoker(
-      [](auto&& callback, auto&& next_callback, auto&&... args) {
-        CONTINUABLE_BLOCK_TRY_BEGIN
-          util::partial_invoke(std::forward<decltype(callback)>(callback),
-                               std::forward<decltype(args)>(args)...);
-          invoke_no_except(
-              std::forward<decltype(next_callback)>(next_callback));
-        CONTINUABLE_BLOCK_TRY_END
-      },
-      traits::identity<>{});
-}
-
-/// Returns a sequenced invoker which is able to invoke
-/// objects where std::get is applicable.
-inline auto sequenced_unpack_invoker() {
-  return [](auto&& callback, auto&& next_callback, auto&&... args) {
-    CONTINUABLE_BLOCK_TRY_BEGIN
-      auto result =
-          util::partial_invoke(std::forward<decltype(callback)>(callback),
-                               std::forward<decltype(args)>(args)...);
-
-      // Workaround for MSVC not capturing the reference correctly inside
-      // the lambda.
-      using Next = decltype(next_callback);
-
-      traits::unpack(std::move(result), [&](auto&&... types) {
-        /// TODO Add inplace resolution here
-
-        invoke_no_except(std::forward<Next>(next_callback),
-                         std::forward<decltype(types)>(types)...);
-      });
-    CONTINUABLE_BLOCK_TRY_END
-  };
-} // namespace decoration
-
-// - std::pair<?, ?> -> next_callback(?, ?)
-template <typename First, typename Second>
-constexpr auto invoker_of(traits::identity<std::pair<First, Second>>) {
-  return make_invoker(sequenced_unpack_invoker(),
-                      traits::identity<First, Second>{});
-}
-
-// - std::tuple<?...>  -> next_callback(?...)
-template <typename... Args>
-constexpr auto invoker_of(traits::identity<std::tuple<Args...>>) {
-  return make_invoker(sequenced_unpack_invoker(), traits::identity<Args...>{});
-}
-
-#undef CONTINUABLE_BLOCK_TRY_BEGIN
-#undef CONTINUABLE_BLOCK_TRY_END
-} // namespace decoration
-
-/// Invoke the callback immediately
-template <typename Invoker, typename... Args>
-void packed_dispatch(types::this_thread_executor_tag, Invoker&& invoker,
-                     Args&&... args) {
-
-  // Invoke the callback with the decorated invoker immediately
-  std::forward<Invoker>(invoker)(std::forward<Args>(args)...);
-}
-
-/// Invoke the callback through the given executor
-template <typename Executor, typename Invoker, typename... Args>
-void packed_dispatch(Executor&& executor, Invoker&& invoker, Args&&... args) {
-
-  // Create a worker object which when invoked calls the callback with the
-  // the returned arguments.
-  auto work = [
-    invoker = std::forward<Invoker>(invoker),
-    args = std::make_tuple(std::forward<Args>(args)...)
-  ]() mutable {
-    traits::unpack(std::move(args), [&](auto&&... captured_args) {
-      // Just use the packed dispatch method which dispatches the work on
-      // the current thread.
-      packed_dispatch(types::this_thread_executor_tag{}, std::move(invoker),
-                      std::forward<decltype(captured_args)>(captured_args)...);
-    });
-  };
-
-  // Pass the work callable object to the executor
-  std::forward<Executor>(executor)(std::move(work));
-}
-
-/// Tells whether we potentially move the chain upwards and handle the result
-enum class handle_results {
-  no, //< The result is forwarded to the next callable
-  yes //< The result is handled by the current callable
-};
-
-// Silences a doxygen bug, it tries to map forward to std::forward
-/// \cond false
-/// Tells whether we handle the error through the callback
-enum class handle_errors {
-  no,     //< The error is forwarded to the next callable
-  plain,  //< The error is the only argument accepted by the callable
-  forward //< The error is forwarded to the callable while keeping its tag
-};
-/// \endcond
-
-namespace callbacks {
-namespace proto {
-template <handle_results HandleResults, typename Base, typename Hint>
-struct result_handler_base;
-template <typename Base, typename... Args>
-struct result_handler_base<handle_results::no, Base,
-                           hints::signature_hint_tag<Args...>> {
-  void operator()(Args... args) && {
-    // Forward the arguments to the next callback
-    std::move(static_cast<Base*>(this)->next_callback_)(std::move(args)...);
-  }
-};
-template <typename Base, typename... Args>
-struct result_handler_base<handle_results::yes, Base,
-                           hints::signature_hint_tag<Args...>> {
-  /// The operator which is called when the result was provided
-  void operator()(Args... args) && {
-    // In order to retrieve the correct decorator we must know what the
-    // result type is.
-    auto result = traits::identify<decltype(util::partial_invoke(
-        std::move(static_cast<Base*>(this)->callback_), std::move(args)...))>{};
-
-    // Pick the correct invoker that handles decorating of the result
-    auto invoker = decoration::invoker_of(result);
-
-    // Invoke the callback
-    packed_dispatch(std::move(static_cast<Base*>(this)->executor_),
-                    std::move(invoker),
-                    std::move(static_cast<Base*>(this)->callback_),
-                    std::move(static_cast<Base*>(this)->next_callback_),
-                    std::move(args)...);
-  }
-};
-
-inline auto make_error_invoker(
-    std::integral_constant<handle_errors, handle_errors::plain>) noexcept {
-  return [](auto&& callback, types::error_type&& error) {
-    // Errors are not partial invoked
-    // NOLINTNEXTLINE(hicpp-move-const-arg)
-    std::forward<decltype(callback)>(callback)(std::move(error));
-  };
-}
-inline auto make_error_invoker(
-    std::integral_constant<handle_errors, handle_errors::forward>) noexcept {
-  return [](auto&& callback, types::error_type&& error) {
-    // Errors are not partial invoked
-    std::forward<decltype(callback)>(callback)(
-        types::dispatch_error_tag{},
-        std::move(error)); // NOLINT(hicpp-move-const-arg)
-  };
-}
-
-template <handle_errors HandleErrors /* = plain or forward*/, typename Base>
-struct error_handler_base {
-  void operator()(types::dispatch_error_tag, types::error_type error) && {
-    // Just invoke the error handler, cancel the calling hierarchy after
-    auto invoker = make_error_invoker(
-        std::integral_constant<handle_errors, HandleErrors>{});
-
-    // Invoke the error handler
-    packed_dispatch(
-        std::move(static_cast<Base*>(this)->executor_), std::move(invoker),
-        std::move(static_cast<Base*>(this)->callback_), std::move(error));
-  }
-};
-template <typename Base>
-struct error_handler_base<handle_errors::no, Base> {
-  /// The operator which is called when an error occurred
-  void operator()(types::dispatch_error_tag tag, types::error_type error) && {
-    // Forward the error to the next callback
-    std::move(static_cast<Base*>(this)->next_callback_)(tag, std::move(error));
-  }
-};
-} // namespace proto
-
-template <typename Hint, handle_results HandleResults,
-          handle_errors HandleErrors, typename Callback, typename Executor,
-          typename NextCallback>
-struct callback_base;
-
-template <typename... Args, handle_results HandleResults,
-          handle_errors HandleErrors, typename Callback, typename Executor,
-          typename NextCallback>
-struct callback_base<hints::signature_hint_tag<Args...>, HandleResults,
-                     HandleErrors, Callback, Executor, NextCallback>
-    : proto::result_handler_base<
-          HandleResults,
-          callback_base<hints::signature_hint_tag<Args...>, HandleResults,
-                        HandleErrors, Callback, Executor, NextCallback>,
-          hints::signature_hint_tag<Args...>>,
-      proto::error_handler_base<
-          HandleErrors,
-          callback_base<hints::signature_hint_tag<Args...>, HandleResults,
-                        HandleErrors, Callback, Executor, NextCallback>>,
-      util::non_copyable {
-
-  Callback callback_;
-  Executor executor_;
-  NextCallback next_callback_;
-
-  explicit callback_base(Callback callback, Executor executor,
-                         NextCallback next_callback)
-      : callback_(std::move(callback)), executor_(std::move(executor)),
-        next_callback_(std::move(next_callback)) {
-  }
-
-  /// Pull the result handling operator() in
-  using proto::result_handler_base<
-      HandleResults,
-      callback_base<hints::signature_hint_tag<Args...>, HandleResults,
-                    HandleErrors, Callback, Executor, NextCallback>,
-      hints::signature_hint_tag<Args...>>::operator();
-
-  /// Pull the error handling operator() in
-  using proto::error_handler_base<
-      HandleErrors,
-      callback_base<hints::signature_hint_tag<Args...>, HandleResults,
-                    HandleErrors, Callback, Executor, NextCallback>>::
-  operator();
-
-  /// Resolves the continuation with the given values
-  void set_value(Args... args) {
-    std::move (*this)(std::move(args)...);
-  }
-
-  /// Resolves the continuation with the given error variable.
-  void set_exception(types::error_type error) {
-    std::move (*this)(types::dispatch_error_tag{}, std::move(error));
-  }
-};
-
-template <typename Hint, handle_results HandleResults,
-          handle_errors HandleErrors, typename Callback, typename Executor,
-          typename NextCallback>
-auto make_callback(Callback&& callback, Executor&& executor,
-                   NextCallback&& next_callback) {
-  return callback_base<Hint, HandleResults, HandleErrors,
-                       std::decay_t<Callback>, std::decay_t<Executor>,
-                       std::decay_t<NextCallback>>{
-      std::forward<Callback>(callback), std::forward<Executor>(executor),
-      std::forward<NextCallback>(next_callback)};
-}
-
-/// Once this was a workaround for GCC bug:
-/// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64095
-struct final_callback : util::non_copyable {
-  template <typename... Args>
-  void operator()(Args... /*args*/) && {
-  }
-
-  void operator()(types::dispatch_error_tag, types::error_type error) && {
-    (void)error;
-#ifndef CONTINUABLE_WITH_UNHANDLED_EXCEPTIONS
-    // There were unhandled errors inside the asynchronous call chain!
-    // Define `CONTINUABLE_WITH_UNHANDLED_EXCEPTIONS` in order
-    // to ignore unhandled errors!"
-    util::trap();
-#endif // CONTINUABLE_WITH_UNHANDLED_EXCEPTIONS
-  }
-
-  template <typename... Args>
-  void set_value(Args... args) {
-    std::move (*this)(std::forward<Args>(args)...);
-  }
-
-  void set_exception(types::error_type error) {
-    // NOLINTNEXTLINE(hicpp-move-const-arg)
-    std::move (*this)(types::dispatch_error_tag{}, std::move(error));
-  }
-};
-} // namespace callbacks
-
-/// Returns the next hint when the callback is invoked with the given hint
-template <typename T, typename... Args>
-constexpr auto
-next_hint_of(std::integral_constant<handle_results, handle_results::yes>,
-             traits::identity<T> /*callback*/,
-             hints::signature_hint_tag<Args...> /*current*/) {
-  // Partial Invoke the given callback
-  using Result = decltype(
-      util::partial_invoke(std::declval<T>(), std::declval<Args>()...));
-
-  // Return the hint of thr given invoker
-  return decltype(decoration::invoker_of(traits::identify<Result>{}).hint()){};
-}
-/// Don't progress the hint when we don't continue
-template <typename T, typename... Args>
-constexpr auto
-next_hint_of(std::integral_constant<handle_results, handle_results::no>,
-             traits::identity<T> /*callback*/,
-             hints::signature_hint_tag<Args...> current) {
-  return current;
-}
-
-/// Chains a callback together with a continuation and returns a continuation:
-///
-/// For example given:
-/// - Continuation: continuation<[](auto&& callback) { callback("hi"); }>
-/// - Callback: [](std::string) { }
-///
-/// This function returns a function accepting the next callback in the chain:
-/// - Result: continuation<[](auto&& callback) { /*...*/ }>
-///
-template <handle_results HandleResults, handle_errors HandleErrors,
-          typename Continuation, typename Callback, typename Executor>
-auto chain_continuation(Continuation&& continuation, Callback&& callback,
-                        Executor&& executor) {
-  static_assert(is_continuable<std::decay_t<Continuation>>{},
-                "Expected a continuation!");
-
-  using Hint = decltype(hints::hint_of(traits::identify<Continuation>()));
-  constexpr auto next_hint =
-      next_hint_of(std::integral_constant<handle_results, HandleResults>{},
-                   traits::identify<decltype(callback)>{}, Hint{});
-
-  // TODO consume only the data here so the freeze isn't needed
-  auto ownership_ = attorney::ownership_of(continuation);
-  continuation.freeze();
-
-  return attorney::create(
-      [
-        continuation = std::forward<Continuation>(continuation),
-        callback = std::forward<Callback>(callback),
-        executor = std::forward<Executor>(executor)
-      ](auto&& next_callback) mutable {
-
-        // Invokes a continuation with a given callback.
-        // Passes the next callback to the resulting continuable or
-        // invokes the next callback directly if possible.
-        //
-        // For example given:
-        // - Continuation: continuation<[](auto&& callback) { callback("hi"); }>
-        // - Callback: [](std::string) { }
-        // - NextCallback: []() { }
-        auto proxy =
-            callbacks::make_callback<Hint, HandleResults, HandleErrors>(
-                std::move(callback), std::move(executor),
-                std::forward<decltype(next_callback)>(next_callback));
-
-        // Invoke the continuation with a proxy callback.
-        // The proxy callback is responsible for passing
-        // the result to the callback as well as decorating it.
-        attorney::invoke_continuation(std::move(continuation),
-                                      std::move(proxy));
-      },
-      next_hint, ownership_);
-}
-
-/// Final invokes the given continuation chain:
-///
-/// For example given:
-/// - Continuation: continuation<[](auto&& callback) { callback("hi"); }>
-template <typename Continuation>
-void finalize_continuation(Continuation&& continuation) {
-  attorney::invoke_continuation(std::forward<Continuation>(continuation),
-                                callbacks::final_callback{});
-}
-
-/// Workaround for GCC bug:
-/// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64095
-template <typename T>
-class supplier_callback {
-  T data_;
-
-public:
-  explicit supplier_callback(T data) : data_(std::move(data)) {
-  }
-
-  template <typename... Args>
-  auto operator()(Args...) {
-    return std::move(data_);
-  }
-};
-
-/// Returns a continuable into a callable object returning the continuable
-template <typename Continuation>
-auto wrap_continuation(Continuation&& continuation) {
-  continuation.freeze();
-  return supplier_callback<std::decay_t<Continuation>>(
-      std::forward<Continuation>(continuation));
-}
-} // namespace base
-} // namespace detail
-} // namespace cti
-
-#endif // CONTINUABLE_DETAIL_BASE_HPP_INCLUDED

include/continuable/detail/connection/connection-aggregated.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -35,11 +35,10 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/continuable-result.hpp>
 #include <continuable/continuable-traverse.hpp>
-#include <continuable/detail/base.hpp>
+#include <continuable/detail/core/base.hpp>
-#include <continuable/detail/flat-variant.hpp>
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/traits.hpp>
 
 namespace cti {
 namespace detail {
@@ -55,62 +54,69 @@ namespace connection {
 ///   - single async value -> single value
 ///   - multiple async value -> tuple of async values.
 namespace aggregated {
+
 /// Guards a type to be default constructible,
 /// and wraps it into an optional type if it isn't default constructible.
 template <typename T>
 using lazy_value_t = std::conditional_t<std::is_default_constructible<T>::value,
-                                        T, container::flat_variant<T>>;
+                                        T, result<T>>;
 
 template <typename T>
-decltype(auto) unpack_lazy(T&& value) {
+decltype(auto) unpack_lazy(std::true_type /*is_default_constructible*/,
+                           T&& value) {
   return std::forward<T>(value);
 }
 template <typename T>
-T&& unpack_lazy(container::flat_variant<T>&& value) {
+T&& unpack_lazy(std::false_type /*is_default_constructible*/,
-  assert(value.template is<T>() &&
+                result<T>&& value) {
+  assert(value.is_value() &&
          "The connection was finalized before all values were present!");
 
-  return std::move(value.template cast<T>());
+  return std::move(value).get_value();
 }
 
 template <typename Continuable>
 class continuable_box;
 template <typename Data>
-class continuable_box<continuable_base<Data, hints::signature_hint_tag<>>> {
+class continuable_box<continuable_base<Data, identity<>>> {
 
-  continuable_base<Data, hints::signature_hint_tag<>> continuable_;
+  continuable_base<Data, identity<>> continuable_;
 
 public:
-  explicit continuable_box(
+  explicit continuable_box(continuable_base<Data, identity<>>&& continuable)
-      continuable_base<Data, hints::signature_hint_tag<>>&& continuable)
+    : continuable_(std::move(continuable)) {}
-      : continuable_(std::move(continuable)) {
+
+  auto const& peek() const {
+    return continuable_;
   }
 
-  continuable_base<Data, hints::signature_hint_tag<>>&& fetch() {
+  auto&& fetch() {
     return std::move(continuable_);
   }
 
-  void assign() {
+  void assign() {}
-  }
 
   auto unbox() && {
     return spread_this();
   }
 };
-template <typename Data, typename First>
-class continuable_box<
-    continuable_base<Data, hints::signature_hint_tag<First>>> {
 
-  continuable_base<Data, hints::signature_hint_tag<First>> continuable_;
+template <typename Data, typename First>
+class continuable_box<continuable_base<Data, identity<First>>> {
+
+  continuable_base<Data, identity<First>> continuable_;
   lazy_value_t<First> first_;
 
 public:
   explicit continuable_box(
-      continuable_base<Data, hints::signature_hint_tag<First>>&& continuable)
+      continuable_base<Data, identity<First>>&& continuable)
-      : continuable_(std::move(continuable)) {
+    : continuable_(std::move(continuable)) {}
+
+  auto const& peek() const {
+    return continuable_;
   }
 
-  continuable_base<Data, hints::signature_hint_tag<First>>&& fetch() {
+  auto&& fetch() {
     return std::move(continuable_);
   }
 
@@ -119,27 +125,27 @@ public:
   }
 
   auto unbox() && {
-    return unpack_lazy(std::move(first_));
+    return unpack_lazy(std::is_default_constructible<First>{},
+                       std::move(first_));
   }
 };
 template <typename Data, typename First, typename Second, typename... Rest>
 class continuable_box<
-    continuable_base<Data, hints::signature_hint_tag<First, Second, Rest...>>> {
+    continuable_base<Data, identity<First, Second, Rest...>>> {
 
-  continuable_base<Data, hints::signature_hint_tag<First, Second, Rest...>>
+  continuable_base<Data, identity<First, Second, Rest...>> continuable_;
-      continuable_;
   lazy_value_t<std::tuple<First, Second, Rest...>> args_;
 
 public:
   explicit continuable_box(
-      continuable_base<Data,
+      continuable_base<Data, identity<First, Second, Rest...>>&& continuable)
-                       hints::signature_hint_tag<First, Second, Rest...>>&&
+    : continuable_(std::move(continuable)) {}
-          continuable)
+
-      : continuable_(std::move(continuable)) {
+  auto const& peek() const {
+    return continuable_;
   }
 
-  continuable_base<Data, hints::signature_hint_tag<First, Second, Rest...>>&&
+  auto&& fetch() {
-  fetch() {
     return std::move(continuable_);
   }
 
@@ -149,9 +155,13 @@ public:
   }
 
   auto unbox() && {
-    return traits::unpack(unpack_lazy(std::move(args_)), [](auto&&... args) {
+    return traits::unpack(
-      return spread_this(std::forward<decltype(args)>(args)...);
+        [](auto&&... args) {
-    });
+          return spread_this(std::forward<decltype(args)>(args)...);
+        },
+        unpack_lazy(
+            std::is_default_constructible<std::tuple<First, Second, Rest...>>{},
+            std::move(args_)));
   }
 };
 
@@ -200,21 +210,20 @@ constexpr auto unbox_continuables(Args&&... args) {
 
 namespace detail {
 template <typename Callback, typename Data>
-constexpr auto finalize_impl(traits::identity<void>, Callback&& callback,
+constexpr auto finalize_impl(identity<void>, Callback&& callback, Data&&) {
-                             Data&&) {
   return std::forward<Callback>(callback)();
 }
 template <typename... Args, typename Callback, typename Data>
-constexpr auto finalize_impl(traits::identity<std::tuple<Args...>>,
+constexpr auto finalize_impl(identity<std::tuple<Args...>>, Callback&& callback,
-                             Callback&& callback, Data&& data) {
+                             Data&& data) {
   // Call the final callback with the cleaned result
-  return traits::unpack(unbox_continuables(std::forward<Data>(data)),
+  return traits::unpack(std::forward<Callback>(callback),
-                        std::forward<Callback>(callback));
+                        unbox_continuables(std::forward<Data>(data)));
 }
 
 struct hint_mapper {
   template <typename... T>
-  constexpr auto operator()(T...) -> hints::signature_hint_tag<T...> {
+  constexpr auto operator()(T...) -> identity<T...> {
     return {};
   }
 };
@@ -224,7 +233,7 @@ template <typename Callback, typename Data>
 constexpr auto finalize_data(Callback&& callback, Data&& data) {
   using result_t = decltype(unbox_continuables(std::forward<Data>(data)));
   // Guard the final result against void
-  return detail::finalize_impl(traits::identity<std::decay_t<result_t>>{},
+  return detail::finalize_impl(identity<std::decay_t<result_t>>{},
                                std::forward<Callback>(callback),
                                std::forward<Data>(data));
 }

include/continuable/detail/connection/connection-all.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -37,13 +37,13 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/continuable-primitives.hpp>
-#include <continuable/detail/base.hpp>
+#include <continuable/detail/connection/connection-aggregated.hpp>
-#include <continuable/detail/connection-aggregated.hpp>
+#include <continuable/detail/connection/connection.hpp>
-#include <continuable/detail/connection.hpp>
+#include <continuable/detail/core/annotation.hpp>
-#include <continuable/detail/hints.hpp>
+#include <continuable/detail/core/base.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/core/types.hpp>
-#include <continuable/detail/types.hpp>
+#include <continuable/detail/utility/traits.hpp>
 
 namespace cti {
 namespace detail {
@@ -99,11 +99,11 @@ class result_submitter
     }
 
     template <typename... PartialArgs>
-    void operator()(types::dispatch_error_tag tag, types::error_type error) && {
+    void operator()(exception_arg_t tag, exception_t exception) && {
       // We never complete the connection, but we forward the first error
       // which was raised.
       std::call_once(me->flag_, std::move(me->callback_), tag,
-                     std::move(error));
+                     std::move(exception));
     }
   };
 
@@ -157,22 +157,21 @@ struct connection_finalizer<connection_strategy_all_tag> {
   template <typename Connection>
   static auto finalize(Connection&& connection, util::ownership ownership) {
     // Create the target result from the connection
-    auto result =
+    auto res =
         aggregated::box_continuables(std::forward<Connection>(connection));
 
-    auto signature = aggregated::hint_of_data<decltype(result)>();
+    auto signature = aggregated::hint_of_data<decltype(res)>();
-
-    return base::attorney::create(
-        [result = std::move(result)](auto&& callback) mutable {
 
+    return base::attorney::create_from(
+        [res = std::move(res)](auto&& callback) mutable {
           using submitter_t =
               all::result_submitter<std::decay_t<decltype(callback)>,
-                                    std::decay_t<decltype(result)>>;
+                                    std::decay_t<decltype(res)>>;
 
-          // Create the shared state which holds the result and the final
+          // Create the shared state which holds the result
-          // callback
+          // and the final callback
           auto state = std::make_shared<submitter_t>(
-              std::forward<decltype(callback)>(callback), std::move(result));
+              std::forward<decltype(callback)>(callback), std::move(res));
 
           // Dispatch the continuables and store its partial result
           // in the whole result
@@ -186,6 +185,13 @@ struct connection_finalizer<connection_strategy_all_tag> {
   }
 };
 } // namespace connection
+
+/// Specialization for a connection annotation
+template <>
+struct annotation_trait<connection::connection_strategy_all_tag>
+    : connection::connection_annotation_trait<
+          connection::connection_strategy_all_tag> {};
+
 } // namespace detail
 } // namespace cti
 

include/continuable/detail/connection/connection-any.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -37,14 +37,14 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/continuable-primitives.hpp>
 #include <continuable/continuable-promise-base.hpp>
 #include <continuable/continuable-traverse.hpp>
-#include <continuable/detail/base.hpp>
+#include <continuable/detail/core/annotation.hpp>
-#include <continuable/detail/container-category.hpp>
+#include <continuable/detail/core/base.hpp>
-#include <continuable/detail/hints.hpp>
+#include <continuable/detail/core/types.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/traversal/container-category.hpp>
-#include <continuable/detail/types.hpp>
+#include <continuable/detail/utility/traits.hpp>
 
 namespace cti {
 namespace detail {
@@ -88,30 +88,30 @@ private:
 
 struct result_deducer {
   template <typename T>
-  static auto deduce_one(std::false_type, traits::identity<T>) {
+  static auto deduce_one(std::false_type, identity<T>) {
     static_assert(traits::fail<T>::value,
                   "Non continuable types except tuple like and homogeneous "
                   "containers aren't allowed inside an any expression!");
   }
   template <typename T>
-  static auto deduce_one(std::true_type, traits::identity<T> id) {
+  static auto deduce_one(std::true_type, identity<T> id) {
-    return hints::hint_of(id);
+    return base::annotation_of(id);
   }
   template <typename T>
   static auto deduce(traversal::container_category_tag<false, false>,
-                     traits::identity<T> id) {
+                     identity<T> id) {
     return deduce_one<T>(base::is_continuable<T>{}, id);
   }
 
   /// Deduce a homogeneous container
   template <bool IsTupleLike, typename T>
   static auto deduce(traversal::container_category_tag<true, IsTupleLike>,
-                     traits::identity<T>) {
+                     identity<T>) {
 
     // Deduce the containing type
     using element_t = std::decay_t<decltype(*std::declval<T>().begin())>;
     return deduce(traversal::container_category_of_t<element_t>{},
-                  traits::identity<element_t>{});
+                  identity<element_t>{});
   }
 
   template <typename First, typename... T>
@@ -125,19 +125,18 @@ struct result_deducer {
 
   template <std::size_t... I, typename T>
   static auto deduce_tuple_like(std::integer_sequence<std::size_t, I...>,
-                                traits::identity<T>) {
+                                identity<T>) {
 
     return deduce_same_hints(deduce(
         traversal::container_category_of_t<
             std::decay_t<decltype(std::get<I>(std::declval<T>()))>>{},
-        traits::identity<
+        identity<std::decay_t<decltype(std::get<I>(std::declval<T>()))>>{})...);
-            std::decay_t<decltype(std::get<I>(std::declval<T>()))>>{})...);
   }
 
   /// Traverse tuple like container
   template <typename T>
   static auto deduce(traversal::container_category_tag<false, true>,
-                     traits::identity<T> id) {
+                     identity<T> id) {
 
     constexpr auto const size = std::tuple_size<T>::value;
     return deduce_tuple_like(std::make_index_sequence<size>{}, id);
@@ -172,12 +171,11 @@ struct connection_finalizer<connection_strategy_any_tag> {
   static auto finalize(Connection&& connection, util::ownership ownership) {
     constexpr auto const signature = decltype(any::result_deducer::deduce(
         traversal::container_category_of_t<std::decay_t<Connection>>{},
-        traits::identity<std::decay_t<Connection>>{})){};
+        identity<std::decay_t<Connection>>{})){};
 
-    return base::attorney::create(
+    return base::attorney::create_from(
         [connection =
              std::forward<Connection>(connection)](auto&& callback) mutable {
-
           using submitter_t =
               any::any_result_submitter<std::decay_t<decltype(callback)>>;
 
@@ -193,6 +191,13 @@ struct connection_finalizer<connection_strategy_any_tag> {
   }
 };
 } // namespace connection
+
+/// Specialization for a connection annotation
+template <>
+struct annotation_trait<connection::connection_strategy_any_tag>
+    : connection::connection_annotation_trait<
+          connection::connection_strategy_any_tag> {};
+
 } // namespace detail
 } // namespace cti
 

include/continuable/detail/connection/connection-seq.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -36,12 +36,12 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/continuable-primitives.hpp>
 #include <continuable/continuable-traverse-async.hpp>
-#include <continuable/detail/base.hpp>
+#include <continuable/detail/connection/connection-aggregated.hpp>
-#include <continuable/detail/connection-aggregated.hpp>
+#include <continuable/detail/core/base.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/util.hpp>
+#include <continuable/detail/utility/util.hpp>
 
 namespace cti {
 namespace detail {
@@ -56,16 +56,16 @@ auto sequential_connect(Left&& left, Right&& right) {
   left.freeze(right.is_frozen());
   right.freeze();
 
-  return std::forward<Left>(left).then([right = std::forward<Right>(right)](
+  return std::forward<Left>(left).then(
-      auto&&... args) mutable {
+      [right = std::forward<Right>(right)](auto&&... args) mutable {
-    return std::move(right).then([previous = std::make_tuple(
+        return std::move(right).then(
-                                      std::forward<decltype(args)>(args)...)](
+            [previous = std::make_tuple(std::forward<decltype(args)>(args)...)](
-        auto&&... args) mutable {
+                auto&&... args) mutable {
-      return traits::merge(
+              return std::tuple_cat(
-          std::move(previous),
+                  std::move(previous),
-          std::make_tuple(std::forward<decltype(args)>(args)...));
+                  std::make_tuple(std::forward<decltype(args)>(args)...));
-    });
+            });
-  });
+      });
 }
 
 template <typename Callback, typename Box>
@@ -94,25 +94,34 @@ public:
 
   template <typename Box, std::enable_if_t<aggregated::is_continuable_box<
                               std::decay_t<Box>>::value>* = nullptr>
-  bool operator()(async_traverse_visit_tag, Box&& /*box*/) {
+  bool operator()(async_traverse_visit_tag, Box&& box) {
-    return false;
+    if (base::attorney::is_ready(box.peek())) {
+      // The result can be resolved directly
+      traits::unpack(
+          [&](auto&&... args) mutable {
+            box.assign(std::forward<decltype(args)>(args)...);
+          },
+          base::attorney::query(box.fetch()));
+      return true;
+    } else {
+      return false;
+    }
   }
 
   template <typename Box, typename N>
   void operator()(async_traverse_detach_tag, Box&& box, N&& next) {
     box.fetch()
-        .then([ box = std::addressof(box),
+        .then([box = std::addressof(box),
-                next = std::forward<N>(next) ](auto&&... args) mutable {
+               next = std::forward<N>(next)](auto&&... args) mutable {
-
           // Assign the result to the target
           box->assign(std::forward<decltype(args)>(args)...);
 
           // Continue the asynchronous sequential traversal
           next();
         })
-        .fail([me = this->shared_from_this()](types::error_type exception) {
+        .fail([me = this->shared_from_this()](exception_t exception) {
           // Abort the traversal when an error occurred
-          std::move(me->data_.callback)(types::dispatch_error_tag{},
+          std::move(me->data_.callback)(exception_arg_t{},
                                         std::move(exception));
         })
         .done();
@@ -138,30 +147,36 @@ struct connection_finalizer<connection_strategy_seq_tag> {
   template <typename Connection>
   static auto finalize(Connection&& connection, util::ownership ownership) {
 
-    auto result =
+    auto res =
         aggregated::box_continuables(std::forward<Connection>(connection));
 
-    auto signature = aggregated::hint_of_data<decltype(result)>();
+    auto signature = aggregated::hint_of_data<decltype(res)>();
-
-    return base::attorney::create(
-        [result = std::move(result)](auto&& callback) mutable {
 
+    return base::attorney::create_from(
+        [res = std::move(res)](auto&& callback) mutable {
           // The data from which the visitor is constructed in-place
           using data_t =
               seq::sequential_dispatch_data<std::decay_t<decltype(callback)>,
-                                            std::decay_t<decltype(result)>>;
+                                            std::decay_t<decltype(res)>>;
 
           // The visitor type
           using visitor_t = seq::sequential_dispatch_visitor<data_t>;
 
           traverse_pack_async(async_traverse_in_place_tag<visitor_t>{},
                               data_t{std::forward<decltype(callback)>(callback),
-                                     std::move(result)});
+                                     std::move(res)});
         },
         signature, std::move(ownership));
   }
 };
 } // namespace connection
+
+/// Specialization for a connection annotation
+template <>
+struct annotation_trait<connection::connection_strategy_seq_tag>
+    : connection::connection_annotation_trait<
+          connection::connection_strategy_seq_tag> {};
+
 } // namespace detail
 } // namespace cti
 

include/continuable/detail/connection/connection.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -35,12 +35,11 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
 #include <continuable/continuable-traverse.hpp>
-#include <continuable/detail/base.hpp>
+#include <continuable/detail/core/base.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/core/types.hpp>
-#include <continuable/detail/types.hpp>
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/util.hpp>
+#include <continuable/detail/utility/util.hpp>
 
 namespace cti {
 namespace detail {
@@ -56,7 +55,7 @@ template <typename... LeftArgs, typename... RightArgs>
 auto chain_connection(std::tuple<LeftArgs...> leftPack,
                       std::tuple<RightArgs...> rightPack) {
 
-  return traits::merge(std::move(leftPack), std::move(rightPack));
+  return std::tuple_cat(std::move(leftPack), std::move(rightPack));
 }
 
 /// Normalizes a continuation to a tuple holding an arbitrary count of
@@ -84,7 +83,7 @@ auto normalize(Strategy /*strategy*/,
 
   // If the right continuation is a different strategy materialize it
   // in order to keep the precedence in cases where: `c1 && (c2 || c3)`.
-  return std::make_tuple(base::attorney::materialize(std::move(continuation)));
+  return std::make_tuple(std::move(continuation).finish());
 }
 /// - The continuable is inside the current strategy state:
 ///   -> return the data of the tuple
@@ -93,7 +92,7 @@ auto normalize(Strategy /*strategy*/,
                continuable_base<Data, Strategy>&& continuation) {
 
   // If we are in the given strategy we can just use the data of the continuable
-  return base::attorney::consume_data(std::move(continuation));
+  return base::attorney::consume(std::move(continuation));
 }
 
 /// Entry function for connecting two continuables with a given strategy.
@@ -115,7 +114,7 @@ auto connect(Strategy strategy, continuable_base<LData, LAnnotation>&& left,
 
   // Return a new continuable containing the tuple and holding
   // the current strategy as annotation.
-  return base::attorney::create(std::move(data), strategy, ownership_);
+  return base::attorney::create_from_raw(std::move(data), strategy, ownership_);
 }
 
 /// All strategies should specialize this class in order to provide:
@@ -125,32 +124,24 @@ auto connect(Strategy strategy, continuable_base<LData, LAnnotation>&& left,
 template <typename Strategy>
 struct connection_finalizer;
 
-/// Finalizes the connection logic of a given connection
+template <typename Strategy>
-template <typename Data, typename Strategy>
+struct connection_annotation_trait {
-auto finalize_connection(continuable_base<Data, Strategy>&& continuation) {
+  /// Finalizes the connection logic of a given connection
-  using finalizer = connection_finalizer<Strategy>;
+  template <typename Continuable>
+  static auto finish(Continuable&& continuable) {
+    using finalizer = connection_finalizer<Strategy>;
 
-  util::ownership ownership = base::attorney::ownership_of(continuation);
+    util::ownership ownership = base::attorney::ownership_of(continuable);
-  auto connection = base::attorney::consume_data(std::move(continuation));
+    auto connection =
+        base::attorney::consume(std::forward<Continuable>(continuable));
 
-  // Return a new continuable which
+    // Return a new continuable which
-  return finalizer::finalize(std::move(connection), std::move(ownership));
+    return finalizer::finalize(std::move(connection), std::move(ownership));
-}
-
-/// A base class from which the continuable may inherit in order to
-/// provide a materializer method which will finalize an oustanding strategy.
-template <typename Continuable, typename = void>
-struct materializer {
-  static constexpr auto&& apply(Continuable&& continuable) {
-    return std::move(continuable);
   }
-};
-template <typename Data, typename Strategy>
-struct materializer<continuable_base<Data, Strategy>,
-                    std::enable_if_t<is_connection_strategy<Strategy>::value>> {
 
-  static constexpr auto apply(continuable_base<Data, Strategy>&& continuable) {
+  template <typename Continuable>
-    return finalize_connection(std::move(continuable));
+  static bool is_ready(Continuable const& /*continuable*/) noexcept {
+    return false;
   }
 };
 
@@ -180,7 +171,7 @@ public:
 
     // Materialize every continuable
     // TODO Actually we would just need to consume the data here
-    return base::attorney::materialize(std::forward<Continuable>(continuable));
+    return std::forward<Continuable>(continuable).finish();
   }
 };
 

include/continuable/detail/core/annotation.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,51 +21,33 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   SOFTWARE.
 **/
 
-#ifndef CONTINUABLE_DETAIL_HINTS_HPP_INCLUDED
+#ifndef CONTINUABLE_DETAIL_ANNOTATION_HPP_INCLUDED
-#define CONTINUABLE_DETAIL_HINTS_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_ANNOTATION_HPP_INCLUDED
 
 #include <type_traits>
-
+#include <continuable/detail/core/types.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/types.hpp>
 
 namespace cti {
 namespace detail {
 namespace hints {
-/// Represents a present signature hint
-template <typename... Args>
-using signature_hint_tag = traits::identity<Args...>;
-
-/// Returns the signature hint of the given continuable
-template <typename Data, typename... Args>
-constexpr auto
-hint_of(traits::identity<continuable_base<Data, signature_hint_tag<Args...>>>) {
-  return hints::signature_hint_tag<Args...>{};
-}
-
 /// Extracts the signature we pass to the internal continuable
 /// from an argument pack as specified by make_continuable.
 ///
 /// This is the overload taking an arbitrary amount of args
 template <typename... HintArgs>
-constexpr auto extract(traits::identity<HintArgs...> hint) {
+struct from_args : std::common_type<signature_arg_t<HintArgs...>> {};
-  return hint;
+template <>
-}
+struct from_args<void> : std::common_type<signature_arg_t<>> {};
-/// \copybrief extract
-///
-/// This is the overload taking a void arg.
-constexpr auto extract(traits::identity<void> /*hint*/) {
-  return traits::identity<>{};
-}
 } // namespace hints
 } // namespace detail
 } // namespace cti
 
-#endif // CONTINUABLE_DETAIL_HINTS_HPP_INCLUDED
+#endif // CONTINUABLE_DETAIL_ANNOTATION_HPP_INCLUDED

include/continuable/detail/core/types.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -31,9 +31,10 @@
 #ifndef CONTINUABLE_DETAIL_TYPES_HPP_INCLUDED
 #define CONTINUABLE_DETAIL_TYPES_HPP_INCLUDED
 
+#include <type_traits>
 #include <utility>
-
 #include <continuable/detail/features.hpp>
+#include <continuable/detail/utility/identity.hpp>
 
 #ifndef CONTINUABLE_WITH_CUSTOM_ERROR_TYPE
 #ifndef CONTINUABLE_WITH_NO_EXCEPTIONS
@@ -51,32 +52,37 @@ namespace detail {
 /// Contains types used globally across the library
 namespace types {
 #ifdef CONTINUABLE_WITH_CUSTOM_ERROR_TYPE
-using error_type = CONTINUABLE_WITH_CUSTOM_ERROR_TYPE;
+using exception_t = CONTINUABLE_WITH_CUSTOM_ERROR_TYPE;
 #else // CONTINUABLE_WITH_CUSTOM_ERROR_TYPE
 #ifndef CONTINUABLE_WITH_NO_EXCEPTIONS
-/// Represents the error type when exceptions are enabled
+/// Represents the exception type when exceptions are enabled
-using error_type = std::exception_ptr;
+using exception_t = std::exception_ptr;
 #else  // CONTINUABLE_WITH_NO_EXCEPTIONS
 /// Represents the error type when exceptions are disabled
-using error_type = std::error_condition;
+using exception_t = std::error_condition;
 #endif // CONTINUABLE_WITH_NO_EXCEPTIONS
 #endif // CONTINUABLE_WITH_CUSTOM_ERROR_TYPE
 
 /// A tag which is used to execute the continuation inside the current thread
 struct this_thread_executor_tag {};
-/// A tag which is used to continue with an error
-struct dispatch_error_tag {};
 
 /// Marks a given callable object as transformation
 template <typename T>
-class transform : T {
+class plain_tag {
+  T value_;
+
 public:
-  explicit transform(T callable) : T(std::move(callable)) {
+  template <typename O, std::enable_if_t<std::is_constructible<
+                            T, std::decay_t<O>>::value>* = nullptr>
+  /* implicit */ plain_tag(O&& value) : value_(std::forward<O>(value)) {
+  }
+  explicit plain_tag(T value) : value_(std::move(value)) {
   }
 
-  using T::operator();
+  T&& consume() && {
+    return std::move(value_);
+  }
 };
-
 } // namespace types
 } // namespace detail
 } // namespace cti

include/continuable/detail/expected.hpp

@@ -1,164 +0,0 @@
-
-/*
-
-                        /~` _  _ _|_. _     _ |_ | _
-                        \_,(_)| | | || ||_|(_||_)|(/_
-
-                    https://github.com/Naios/continuable
-                                   v3.0.0
-
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
-
-  Permission is hereby granted, free of charge, to any person obtaining a copy
-  of this software and associated documentation files(the "Software"), to deal
-  in the Software without restriction, including without limitation the rights
-  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
-  copies of the Software, and to permit persons to whom the Software is
-  furnished to do so, subject to the following conditions :
-
-  The above copyright notice and this permission notice shall be included in
-  all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
-  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-  SOFTWARE.
-**/
-
-#ifndef CONTINUABLE_DETAIL_EXPECTED_HPP_INCLUDED
-#define CONTINUABLE_DETAIL_EXPECTED_HPP_INCLUDED
-
-#include <type_traits>
-#include <utility>
-
-#include <continuable/detail/flat-variant.hpp>
-#include <continuable/detail/hints.hpp>
-#include <continuable/detail/types.hpp>
-
-namespace cti {
-namespace detail {
-namespace container {
-/// A class similar to the one in the expected proposal,
-/// however it is capable of carrying an exception_ptr if
-/// exceptions are used.
-template <typename T>
-class expected {
-  flat_variant<T, types::error_type> variant_;
-
-public:
-  explicit expected() = default;
-  explicit expected(expected const&) = default;
-  explicit expected(expected&&) = default;
-  expected& operator=(expected const&) = default;
-  expected& operator=(expected&&) = default;
-  ~expected() = default;
-
-  explicit expected(T value) : variant_(std::move(value)) {
-  }
-  explicit expected(types::error_type exception)
-      : variant_(std::move(exception)) {
-  }
-
-  expected& operator=(T value) {
-    variant_ = std::move(value);
-    return *this;
-  }
-  expected& operator=(types::error_type exception) {
-    variant_ = std::move(exception);
-    return *this;
-  }
-
-  void set_value(T value) {
-    variant_ = std::move(value);
-  }
-  void set_exception(types::error_type exception) {
-    variant_ = std::move(exception);
-  }
-
-  bool is_value() const noexcept {
-    return variant_.template is<T>();
-  }
-  bool is_exception() const noexcept {
-    return variant_.template is<types::error_type>();
-  }
-
-  explicit constexpr operator bool() const noexcept {
-    return is_value();
-  }
-
-  T& get_value() noexcept {
-    return variant_.template cast<T>();
-  }
-  T const& get_value() const noexcept {
-    return variant_.template cast<T>();
-  }
-  types::error_type& get_exception() noexcept {
-    return variant_.template cast<types::error_type>();
-  }
-  types::error_type const& get_exception() const noexcept {
-    return variant_.template cast<types::error_type>();
-  }
-
-  T& operator*() noexcept {
-    return get_value();
-  }
-  T const& operator*() const noexcept {
-    return get_value();
-  }
-};
-
-namespace detail {
-struct void_guard_tag {};
-
-template <typename T>
-struct expected_result_trait;
-template <>
-struct expected_result_trait<traits::identity<>> {
-  using expected_type = expected<void_guard_tag>;
-
-  static constexpr void_guard_tag wrap() noexcept {
-    return {};
-  }
-  static void unwrap(expected_type&& e) {
-    assert(e.is_value());
-    (void)e;
-  }
-};
-template <typename T>
-struct expected_result_trait<traits::identity<T>> {
-  using expected_type = expected<T>;
-
-  static auto wrap(T arg) {
-    return std::move(arg);
-  }
-  static auto unwrap(expected_type&& e) {
-    assert(e.is_value());
-    return std::move(e.get_value());
-  }
-};
-template <typename First, typename Second, typename... Rest>
-struct expected_result_trait<traits::identity<First, Second, Rest...>> {
-  using expected_type = expected<std::tuple<First, Second, Rest...>>;
-
-  static auto wrap(First first, Second second, Rest... rest) {
-    return std::make_tuple(std::move(first), std::move(second),
-                           std::move(rest)...);
-  }
-  static auto unwrap(expected_type&& e) {
-    assert(e.is_value());
-    return std::move(e.get_value());
-  }
-};
-} // namespace detail
-
-template <typename Continuable>
-using expected_result_trait_t = detail::expected_result_trait<decltype(
-    hints::hint_of(traits::identify<Continuable>{}))>;
-} // namespace container
-} // namespace detail
-} // namespace cti
-
-#endif // CONTINUABLE_DETAIL_EXPECTED_HPP_INCLUDED

include/continuable/detail/external/asio.hpp

@@ -0,0 +1,242 @@
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_ASIO_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_ASIO_HPP_INCLUDED
+
+#include <array>
+#include <utility>
+#include <continuable/continuable-base.hpp>
+#include <continuable/detail/core/base.hpp>
+#include <continuable/detail/features.hpp>
+
+#if defined(ASIO_STANDALONE)
+#  include <asio/async_result.hpp>
+#  include <asio/error.hpp>
+#  include <asio/error_code.hpp>
+#  include <asio/version.hpp>
+
+#  if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#    include <asio/system_error.hpp>
+#  endif
+
+#  if (ASIO_VERSION < 101300) // 1.13.0
+#    define CTI_DETAIL_ASIO_HAS_NO_INTEGRATION
+#  elif (ASIO_VERSION < 101600) // 1.16.0 (boost 1.72 baseline)
+#    define CTI_DETAIL_ASIO_HAS_EXPLICIT_RET_TYPE_INTEGRATION
+#  endif
+
+#  define CTI_DETAIL_ASIO_NAMESPACE_BEGIN namespace asio {
+#  define CTI_DETAIL_ASIO_NAMESPACE_END }
+#else
+#  include <boost/asio/async_result.hpp>
+#  include <boost/asio/error.hpp>
+#  include <boost/system/error_code.hpp>
+#  include <boost/version.hpp>
+
+#  if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#    include <boost/system/system_error.hpp>
+#  endif
+
+#  if (BOOST_VERSION < 107000) // 1.70
+#    define CTI_DETAIL_ASIO_HAS_NO_INTEGRATION
+#  elif (BOOST_VERSION < 107200) // 1.72
+#    define CTI_DETAIL_ASIO_HAS_EXPLICIT_RET_TYPE_INTEGRATION
+#  endif
+
+#  define CTI_DETAIL_ASIO_NAMESPACE_BEGIN                                      \
+    namespace boost {                                                          \
+    namespace asio {
+#  define CTI_DETAIL_ASIO_NAMESPACE_END                                        \
+    }                                                                          \
+    }
+#endif
+
+#if defined(CTI_DETAIL_ASIO_HAS_NO_INTEGRATION)
+#  error "First-class ASIO support for continuable requires the form of "\
+  "`async_result` with an `initiate` static member function, which was added " \
+  "in standalone ASIO 1.13.0 and Boost ASIO 1.70. Older versions can be " \
+  "integrated manually with `cti::promisify`."
+#endif
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#  include <exception>
+#endif
+
+namespace cti {
+namespace detail {
+namespace asio {
+
+#if defined(ASIO_STANDALONE)
+using error_code_t = ::asio::error_code;
+using basic_errors_t = ::asio::error::basic_errors;
+
+#  if defined(CONTINUABLE_HAS_EXCEPTIONS)
+using system_error_t = ::asio::system_error;
+#  endif
+#else
+using error_code_t = ::boost::system::error_code;
+using basic_errors_t = ::boost::asio::error::basic_errors;
+
+#  if defined(CONTINUABLE_HAS_EXCEPTIONS)
+using system_error_t = ::boost::system::system_error;
+#  endif
+#endif
+
+template <typename Promise, typename Token>
+class promise_resolver {
+public:
+  explicit promise_resolver(Promise promise, Token token)
+    : promise_(std::move(promise))
+    , token_(std::move(token)) {}
+
+  template <typename... T>
+  void operator()(T&&... args) noexcept {
+    promise_.set_value(std::forward<T>(args)...);
+  }
+
+  template <typename... T>
+  void operator()(error_code_t e, T&&... args) noexcept {
+    if (e) {
+      if (!token_.is_ignored(e)) {
+        if (token_.is_cancellation(e)) {
+          promise_.set_canceled();
+          return;
+        } else {
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+          promise_.set_exception(
+              std::make_exception_ptr(system_error_t(std::move(e))));
+#else
+          promise_.set_exception(exception_t(e.value(), e.category()));
+#endif
+          return;
+        }
+      }
+    }
+    promise_.set_value(std::forward<T>(args)...);
+  }
+
+private:
+  Promise promise_;
+  Token token_;
+};
+
+// Binds `promise` to the first argument of a continuable resolver, giving it
+// the signature of an ASIO handler.
+template <typename Promise, typename Token>
+auto promise_resolver_handler(Promise&& promise, Token&& token) noexcept {
+  return promise_resolver<std::decay_t<Promise>, std::decay_t<Token>>(
+      std::forward<Promise>(promise), std::forward<Token>(token));
+}
+
+// Helper struct wrapping a call to `cti::make_continuable` and, if needed,
+// providing an erased, explicit `return_type` for `async_result`.
+template <typename Signature>
+struct initiate_make_continuable;
+
+template <typename... Args>
+struct initiate_make_continuable<void(Args...)> {
+#if defined(CTI_DETAIL_ASIO_HAS_EXPLICIT_RET_TYPE_INTEGRATION)
+  using erased_return_type = continuable<Args...>;
+#endif
+
+  template <typename Continuation>
+  auto operator()(Continuation&& continuation) {
+    return base::attorney::create_from(std::forward<Continuation>(continuation),
+                                       identity<Args...>{}, util::ownership{});
+  }
+};
+
+template <typename... Args>
+struct initiate_make_continuable<void(error_code_t, Args...)> {
+#if defined(CTI_DETAIL_ASIO_HAS_EXPLICIT_RET_TYPE_INTEGRATION)
+  using erased_return_type = continuable<Args...>;
+#endif
+
+  template <typename Continuation>
+  auto operator()(Continuation&& continuation) {
+    return base::attorney::create_from(std::forward<Continuation>(continuation),
+                                       identity<Args...>{}, util::ownership{});
+  }
+};
+
+template <typename... Args>
+struct initiate_make_continuable<void(error_code_t const&, Args...)>
+  : initiate_make_continuable<void(error_code_t, Args...)> {};
+
+struct map_default {
+  constexpr map_default() noexcept {}
+
+  bool is_cancellation(error_code_t const& ec) const noexcept {
+    // Continuable uses a default constructed exception type to signal
+    // cancellation to the followed asynchronous control flow.
+    return ec == basic_errors_t::operation_aborted;
+  }
+  bool is_ignored(error_code_t const& /*ec*/) const noexcept {
+    return false;
+  }
+};
+
+struct map_none {
+  constexpr map_none() noexcept {}
+
+  bool is_cancellation(error_code_t const& /*ec*/) const noexcept {
+    return false;
+  }
+  bool is_ignored(error_code_t const& /*ec*/) const noexcept {
+    return false;
+  }
+};
+
+template <std::size_t Size>
+class map_ignore {
+public:
+  map_ignore(std::array<basic_errors_t, Size> ignored) noexcept
+    : ignored_(ignored) {}
+
+  bool is_cancellation(error_code_t const& ec) const noexcept {
+    return ec == basic_errors_t::operation_aborted;
+  }
+  bool is_ignored(error_code_t const& ec) const noexcept {
+    for (basic_errors_t ignored : ignored_) {
+      if (ec == ignored) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+private:
+  std::array<basic_errors_t, Size> ignored_;
+};
+} // namespace asio
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_ASIO_HPP_INCLUDED

include/continuable/detail/features.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -33,19 +33,19 @@
 
 // Defines CONTINUABLE_WITH_NO_EXCEPTIONS when exception support is disabled
 #ifndef CONTINUABLE_WITH_NO_EXCEPTIONS
-#if defined(_MSC_VER)
+#  if defined(_MSC_VER)
-#if !defined(_HAS_EXCEPTIONS) || (_HAS_EXCEPTIONS == 0)
+#    if !defined(_HAS_EXCEPTIONS) || (_HAS_EXCEPTIONS == 0)
-#define CONTINUABLE_WITH_NO_EXCEPTIONS
+#      define CONTINUABLE_WITH_NO_EXCEPTIONS
-#endif
+#    endif
-#elif defined(__clang__)
+#  elif defined(__clang__)
-#if !(__EXCEPTIONS && __has_feature(cxx_exceptions))
+#    if !(__EXCEPTIONS && __has_feature(cxx_exceptions))
-#define CONTINUABLE_WITH_NO_EXCEPTIONS
+#      define CONTINUABLE_WITH_NO_EXCEPTIONS
-#endif
+#    endif
-#elif defined(__GNUC__)
+#  elif defined(__GNUC__)
-#if !__EXCEPTIONS
+#    if !__EXCEPTIONS
-#define CONTINUABLE_WITH_NO_EXCEPTIONS
+#      define CONTINUABLE_WITH_NO_EXCEPTIONS
-#endif
+#    endif
-#endif
+#  endif
 #endif // CONTINUABLE_WITH_NO_EXCEPTIONS
 
 // clang-format off
@@ -55,8 +55,11 @@
   #define CONTINUABLE_HAS_CXX17_CONSTEXPR_IF
   #define CONTINUABLE_HAS_CXX17_DISJUNCTION
   #define CONTINUABLE_HAS_CXX17_CONJUNCTION
+  #define CONTINUABLE_HAS_CXX17_VOID_T
 #else
   // Generic feature detection based on __has_feature
+  // and other preprocessor definitions based on:
+  // http://en.cppreference.com/w/User:D41D8CD98F/feature_testing_macros
   #if defined(__has_feature)
     #if !defined(CONTINUABLE_HAS_CXX17_CONSTEXPR_IF) &&                        \
         __has_feature(cxx_if_constexpr)
@@ -75,19 +78,49 @@
       (__cpp_lib_experimental_logical_traits >= 201511)
     #define CONTINUABLE_HAS_CXX17_CONJUNCTION
   #endif
+
+  #if !defined(CONTINUABLE_HAS_CXX17_VOID_T) &&                                \
+      defined(__cpp_lib_void_t) &&                                             \
+      (__cpp_lib_void_t >= 201411)
+    #define CONTINUABLE_HAS_CXX17_VOID_T
+  #endif
 #endif
 
-/// Usually this is enabled by the CMake project
+// Automatically detects support for coroutines.
-#if !defined(CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE) &&                        \
+// Parts of this detection mechanism were adapted from boost::asio,
-    defined(__cpp_coroutines) && (__cpp_coroutines >= 201707)
+// with support added for experimental coroutines.
-  #define CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
+#if !defined(CONTINUABLE_HAS_DISABLED_COROUTINE) \
-#endif
+ && !defined(CONTINUABLE_HAS_COROUTINE)
-
+  /// Define CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE when
-/// Define CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE when
+  /// CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE is defined.
-/// CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE is defined.
+  #if defined(CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE)
-#if !defined(CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE) &&                            \
+    #define CONTINUABLE_HAS_COROUTINE 1
-    defined(CONTINUABLE_WITH_EXPERIMENTAL_COROUTINE)
+  #elif defined(CONTINUABLE_WITH_COROUTINE)
-  #define CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE
+    #define CONTINUABLE_HAS_COROUTINE 1
+    #define CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE 1
+  #elif defined(_MSC_VER) // Visual Studio
+    #if (_MSC_VER >= 1928) && (_MSVC_LANG >= 201705)
+      #define CONTINUABLE_HAS_COROUTINE 1
+    #elif _MSC_FULL_VER >= 190023506
+      #if defined(_RESUMABLE_FUNCTIONS_SUPPORTED)
+        #define CONTINUABLE_HAS_COROUTINE 1
+        #define CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE 1
+      #endif // defined(_RESUMABLE_FUNCTIONS_SUPPORTED)
+    #endif // _MSC_FULL_VER >= 190023506
+  #elif defined(__clang__) // Clang
+    #if defined(__cpp_coroutines) && (__cpp_coroutines >= 201703L)
+      #define CONTINUABLE_HAS_COROUTINE 1
+      #if defined(_LIBCPP_EXPERIMENTAL_COROUTINE)
+        #define CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE 1
+      #endif
+    #endif // defined(__cpp_coroutines) && (__cpp_coroutines >= 201703L)
+  #elif defined(__GNUC__) // GCC
+    #if (__cplusplus >= 201709) && (__cpp_impl_coroutine >= 201902)
+      #if __has_include(<coroutine>)
+        #define CONTINUABLE_HAS_COROUTINE 1
+      #endif // __has_include(<coroutine>)
+    #endif // (__cplusplus >= 201709) && (__cpp_impl_coroutine >= 201902)
+  #endif
 #endif
 
 /// Define CONTINUABLE_HAS_EXCEPTIONS when exceptions are used
@@ -97,6 +130,18 @@
 #else
   #undef CONTINUABLE_HAS_EXCEPTIONS
 #endif
+
+/// Define CONTINUABLE_HAS_IMMEDIATE_TYPES when either
+/// - CONTINUABLE_WITH_IMMEDIATE_TYPES is defined
+/// - Building in release mode (NDEBUG is defined)
+///
+/// Build error messages will become more readable in debug mode while
+/// we don't suffer any runtime penalty in release.
+#if defined(CONTINUABLE_WITH_IMMEDIATE_TYPES) || defined(NDEBUG)
+  #define CONTINUABLE_HAS_IMMEDIATE_TYPES 1
+#else
+  #undef CONTINUABLE_HAS_IMMEDIATE_TYPES
+#endif
 // clang-format on
 
 #endif // CONTINUABLE_DETAIL_FEATURES_HPP_INCLUDED

include/continuable/detail/flat-variant.hpp

@@ -1,357 +0,0 @@
-
-/*
-
-                        /~` _  _ _|_. _     _ |_ | _
-                        \_,(_)| | | || ||_|(_||_)|(/_
-
-                    https://github.com/Naios/continuable
-                                   v3.0.0
-
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
-
-  Permission is hereby granted, free of charge, to any person obtaining a copy
-  of this software and associated documentation files(the "Software"), to deal
-  in the Software without restriction, including without limitation the rights
-  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
-  copies of the Software, and to permit persons to whom the Software is
-  furnished to do so, subject to the following conditions :
-
-  The above copyright notice and this permission notice shall be included in
-  all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
-  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-  SOFTWARE.
-**/
-
-#ifndef CONTINUABLE_DETAIL_FLAT_VARIANT_HPP_INCLUDED
-#define CONTINUABLE_DETAIL_FLAT_VARIANT_HPP_INCLUDED
-
-#include <cassert>
-#include <cstdint>
-#include <limits>
-#include <memory>
-#include <type_traits>
-#include <utility>
-
-#include <continuable/detail/traits.hpp>
-
-namespace cti {
-namespace detail {
-namespace container {
-namespace detail {
-// We don't want to pull the algorithm header in
-template <typename... T>
-constexpr std::size_t max_element_of(std::initializer_list<std::size_t> list) {
-  std::size_t m = 0;
-  for (auto current : list) {
-    if (current > m) {
-      m = current;
-    }
-  }
-  return m;
-}
-template <typename... T>
-constexpr auto storage_of_impl() {
-  constexpr auto size = max_element_of({sizeof(T)...});
-  constexpr auto align = max_element_of({alignof(T)...});
-  return std::aligned_storage_t<size, align>{};
-}
-
-/// Declares the aligned storage union for the given types
-template <typename... T>
-using storage_of_t = decltype(storage_of_impl<T...>());
-
-/// The value fpr the empty slot
-using slot_t = std::uint8_t;
-
-/// The value which is used to mark the empty slot
-using empty_slot =
-    std::integral_constant<slot_t, std::numeric_limits<slot_t>::max()>;
-
-template <typename... T>
-struct flat_variant_base {
-  storage_of_t<T...> storage_;
-  slot_t slot_;
-
-  constexpr flat_variant_base() : slot_(empty_slot::value) {
-  }
-
-  flat_variant_base(flat_variant_base const&) noexcept {
-  }
-  flat_variant_base(flat_variant_base&&) noexcept {
-  }
-  flat_variant_base& operator=(flat_variant_base const&) {
-    return *this;
-  }
-  flat_variant_base& operator=(flat_variant_base&&) {
-    return *this;
-  }
-};
-
-template <typename Base>
-struct flat_variant_move_base {
-  constexpr flat_variant_move_base() = default;
-
-  flat_variant_move_base(flat_variant_move_base const&) = default;
-  explicit flat_variant_move_base(flat_variant_move_base&& right) {
-    Base& me = *static_cast<Base*>(this);
-    Base& other = *static_cast<Base*>(&right);
-
-    if (other.is_empty()) {
-      me.set_slot(empty_slot::value);
-    } else {
-
-      other.visit([&](auto&& value) {
-#ifndef NDEBUG
-        me.set_slot(empty_slot::value);
-#endif
-        // NOLINTNEXTLINE(misc-move-forwarding-reference)
-        me.init(std::move(value), other.get_slot());
-      });
-    }
-
-    other.destroy();
-  }
-  flat_variant_move_base& operator=(flat_variant_move_base const&) = default;
-  flat_variant_move_base& operator=(flat_variant_move_base&& right) {
-    Base& me = *static_cast<Base*>(this);
-    Base& other = *static_cast<Base*>(&right);
-
-    me.weak_destroy();
-
-    if (other.is_empty()) {
-      me.set_slot(empty_slot::value);
-    } else {
-      other.visit([&](auto&& value) {
-        // ...
-        me.init(std::move(value), other.get_slot());
-      });
-    }
-    other.destroy();
-    return *this;
-  }
-};
-template <typename Base, bool IsCopyable /*= true*/>
-struct flat_variant_copy_base : flat_variant_move_base<Base> {
-  constexpr flat_variant_copy_base() = default;
-
-  flat_variant_copy_base(flat_variant_copy_base&&) = default;
-  explicit flat_variant_copy_base(flat_variant_copy_base const& right)
-      : flat_variant_move_base<Base>()
-  // TODO noexcept(Base::is_nothrow_move_constructible)
-  {
-    Base& me = *static_cast<Base*>(this);
-    Base const& other = *static_cast<Base const*>(&right);
-
-    if (other.is_empty()) {
-      me.set_slot(empty_slot::value);
-    } else {
-      other.visit([&](auto&& value) {
-#ifndef NDEBUG
-        me.set_slot(empty_slot::value);
-#endif
-        me.init(std::move(value), other.get_slot());
-      });
-    }
-  }
-  flat_variant_copy_base& operator=(flat_variant_copy_base&&) = default;
-  flat_variant_copy_base& operator=(flat_variant_copy_base const& right)
-  // TODO  noexcept(Base::is_nothrow_move_constructible)
-  {
-    Base& me = *static_cast<Base*>(this);
-    Base const& other = *static_cast<Base const*>(&right);
-
-    me.weak_destroy();
-
-    if (other.is_empty()) {
-      me.set_slot(empty_slot::value);
-    } else {
-      other.visit([&](auto&& value) {
-        // ...
-        me.init(std::move(value), other.get_slot());
-      });
-    }
-    return *this;
-  }
-};
-template <typename Base /*, bool IsCopyable = false*/>
-struct flat_variant_copy_base<Base, false> : flat_variant_move_base<Base> {
-  constexpr flat_variant_copy_base() = default;
-
-  flat_variant_copy_base(flat_variant_copy_base const&) = delete;
-  explicit flat_variant_copy_base(flat_variant_copy_base&& right) = default;
-  flat_variant_copy_base& operator=(flat_variant_copy_base const&) = delete;
-  flat_variant_copy_base& operator=(flat_variant_copy_base&&) = default;
-};
-
-/// Deduces to a true_type if all parameters T satisfy the predicate.
-template <template <typename> class Predicate, typename... T>
-using every = traits::conjunction<Predicate<T>...>;
-} // namespace detail
-
-/// A class similar to the one in the variant proposal,
-/// however it is capable of carrying an empty state by default.
-template <typename... T>
-class flat_variant;
-
-template <typename T>
-struct is_flat_variant : std::false_type {};
-template <typename... T>
-struct is_flat_variant<flat_variant<T...>> : std::true_type {};
-
-template <typename... T>
-class flat_variant
-    : detail::flat_variant_copy_base<
-          flat_variant<T...>,
-          detail::every<std::is_copy_constructible, T...>::value>,
-      detail::flat_variant_base<T...> {
-
-  static_assert(sizeof...(T) > 0, "At least one paremeter T is required!");
-
-  template <typename...>
-  friend class flat_variant;
-  template <typename>
-  friend struct detail::flat_variant_move_base;
-  template <typename, bool>
-  friend struct detail::flat_variant_copy_base;
-
-  template <typename V>
-  flat_variant(V&& value, detail::slot_t const slot) {
-#ifndef NDEBUG
-    set_slot(detail::empty_slot::value);
-#endif
-    init(std::forward<V>(value), slot);
-  }
-
-public:
-  constexpr flat_variant() = default;
-  flat_variant(flat_variant const&) = default;
-  flat_variant(flat_variant&&) = default;
-  flat_variant& operator=(flat_variant const&) = default;
-  flat_variant& operator=(flat_variant&&) = default;
-
-  ~flat_variant() noexcept(
-      detail::every<std::is_nothrow_destructible, T...>::value) {
-    weak_destroy();
-  }
-
-  template <
-      typename V,
-      std::enable_if_t<!is_flat_variant<std::decay_t<V>>::value>* = nullptr>
-  // Since the flat_variant isn't allowed through SFINAE
-  // this overload is safed against the linted issue.
-  // NOLINTNEXTLINE(misc-forwarding-reference-overload)
-  explicit flat_variant(V&& value)
-      : flat_variant(std::forward<V>(value),
-                     traits::index_of_t<std::decay_t<V>, T...>::value) {
-  }
-
-  template <
-      typename V,
-      std::enable_if_t<!is_flat_variant<std::decay_t<V>>::value>* = nullptr>
-  flat_variant& operator=(V&& value) {
-    weak_destroy();
-    init(std::forward<V>(value),
-         traits::index_of_t<std::decay_t<V>, T...>::value);
-    return *this;
-  }
-
-  template <typename V, std::size_t Index =
-                            traits::index_of_t<std::decay_t<V>, T...>::value>
-  bool is() const noexcept {
-    return is_slot(Index);
-  }
-
-  bool is_empty() const noexcept {
-    return is_slot(detail::empty_slot::value);
-  }
-
-  explicit constexpr operator bool() const noexcept {
-    return !is_empty();
-  }
-
-  template <typename V>
-  V& cast() noexcept {
-    assert(is_slot(traits::index_of_t<std::decay_t<V>, T...>::value));
-    return *reinterpret_cast<std::decay_t<V>*>(&this->storage_);
-  }
-
-  template <typename V>
-  V const& cast() const noexcept {
-    assert(is_slot(traits::index_of_t<std::decay_t<V>, T...>::value));
-    return *reinterpret_cast<std::decay_t<V> const*>(&this->storage_);
-  }
-
-private:
-  template <typename C, typename V>
-  static void visit_dispatch(flat_variant* me, V&& visitor) {
-    std::forward<V>(visitor)(me->cast<C>());
-  }
-  template <typename C, typename V>
-  static void visit_dispatch_const(flat_variant const* me, V&& visitor) {
-    std::forward<V>(visitor)(me->cast<C>());
-  }
-
-  template <typename V>
-  void visit(V&& visitor) {
-    if (!is_empty()) {
-      using callback_t = void (*)(flat_variant*, V &&);
-      constexpr callback_t const callbacks[] = {&visit_dispatch<T, V>...};
-      callbacks[get_slot()](this, std::forward<V>(visitor));
-    }
-  }
-  template <typename V>
-  void visit(V&& visitor) const {
-    if (!is_empty()) {
-      using callback_t = void (*)(flat_variant const*, V&&);
-      constexpr callback_t const callbacks[] = {&visit_dispatch_const<T, V>...};
-      callbacks[get_slot()](this, std::forward<V>(visitor));
-    }
-  }
-
-  template <typename V>
-  void init(V&& value, detail::slot_t const slot) {
-    assert(is_empty());
-    assert(sizeof(this->storage_) >= sizeof(std::decay_t<V>));
-
-    using type = std::decay_t<V>;
-    new (&this->storage_) type(std::forward<V>(value));
-    set_slot(slot);
-  }
-  void destroy() {
-    weak_destroy();
-
-#ifdef NDEBUG
-    set_slot(detail::empty_slot::value);
-#endif
-  }
-  void weak_destroy() {
-    visit([&](auto&& value) {
-      using type = std::decay_t<decltype(value)>;
-      value.~type();
-    });
-
-#ifndef NDEBUG
-    set_slot(detail::empty_slot::value);
-#endif
-  }
-  detail::slot_t get_slot() const noexcept {
-    return this->slot_;
-  }
-  bool is_slot(detail::slot_t const slot) const noexcept {
-    return get_slot() == slot;
-  }
-  void set_slot(detail::slot_t const slot) {
-    this->slot_ = slot;
-  }
-};
-} // namespace container
-} // namespace detail
-} // namespace cti
-
-#endif // CONTINUABLE_DETAIL_FLAT_VARIANT_HPP_INCLUDED

include/continuable/detail/operations/async.hpp

@@ -0,0 +1,80 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_OPERATIONS_ASYNC_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_OPERATIONS_ASYNC_HPP_INCLUDED
+
+#include <continuable/continuable-base.hpp>
+#include <continuable/detail/core/annotation.hpp>
+#include <continuable/detail/core/base.hpp>
+#include <continuable/detail/utility/identity.hpp>
+
+namespace cti {
+namespace detail {
+namespace operations {
+template <typename Callable, typename Executor, typename... Args>
+auto async(Callable&& callable, Executor&& executor, Args&&... args) {
+  using result_t =
+      decltype(util::invoke(std::forward<decltype(callable)>(callable),
+                            std::forward<decltype(args)>(args)...));
+
+  constexpr auto hint =
+      decltype(base::decoration::invoker_of(identity<result_t>{}))::hint();
+
+  auto continuation = [callable = std::forward<decltype(callable)>(callable),
+                       executor = std::forward<decltype(executor)>(executor),
+                       args = std::make_tuple(std::forward<decltype(args)>(
+                           args)...)](auto&& promise) mutable {
+    auto invoker = base::decoration::invoker_of(identity<result_t>{});
+
+    using promise_t = decltype(promise);
+
+    // Invoke the callback
+    traits::unpack(
+        [&](auto&&... args) mutable {
+          // Invoke the promise through the dedicated invoker
+          // and through the given executor
+          base::on_executor(std::move(executor), std::move(invoker),
+                            std::move(callable),
+                            std::forward<promise_t>(promise),
+                            std::forward<decltype(args)>(args)...);
+        },
+        std::move(args));
+  };
+
+  return base::attorney::create_from(std::move(continuation), //
+                                     hint, util::ownership{});
+}
+} // namespace operations
+
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_OPERATIONS_ASYNC_HPP_INCLUDED

include/continuable/detail/operations/loop.hpp

@@ -0,0 +1,180 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_OPERATIONS_LOOP_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_OPERATIONS_LOOP_HPP_INCLUDED
+
+#include <cassert>
+#include <memory>
+#include <tuple>
+#include <type_traits>
+#include <continuable/continuable-base.hpp>
+#include <continuable/continuable-result.hpp>
+#include <continuable/detail/features.hpp>
+#include <continuable/detail/utility/traits.hpp>
+#include <continuable/detail/utility/util.hpp>
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#include <exception>
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+
+namespace cti {
+namespace detail {
+template <typename T>
+struct loop_trait {
+  static_assert(!std::is_same<T, T>::value,
+                "The callable passed to cti::loop must always return a "
+                "cti::continuable_base which resolves to a cti::result.");
+};
+
+template <typename... Args>
+struct loop_trait<identity<result<Args...>>> {
+  template <typename Callable>
+  static auto make(Callable&& callable) {
+    return make_continuable<Args...>(std::forward<Callable>(callable));
+  }
+};
+template <>
+struct loop_trait<identity<result<>>> {
+  template <typename Callable>
+  static auto make(Callable&& callable) {
+    return make_continuable<void>(std::forward<Callable>(callable));
+  }
+};
+
+namespace operations {
+template <typename Promise, typename Callable, typename ArgsTuple>
+class loop_frame : public std::enable_shared_from_this<
+                       loop_frame<Promise, Callable, ArgsTuple>> {
+  Promise promise_;
+  Callable callable_;
+  ArgsTuple args_;
+
+public:
+  explicit loop_frame(Promise promise, Callable callable, ArgsTuple args)
+      : promise_(std::move(promise)), callable_(std::move(callable)),
+        args_(std::move(args)) {
+  }
+
+  void loop() {
+    // MSVC can't evaluate this inside the lambda capture
+    auto me = this->shared_from_this();
+
+    traits::unpack(
+        [&](auto&&... args) mutable {
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+          try {
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+
+            util::invoke(callable_, std::forward<decltype(args)>(args)...)
+                .next([me = std::move(me)](auto&&... args) {
+                  me->resolve(std::forward<decltype(args)>(args)...);
+                });
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+          } catch (...) {
+            me->resolve(exception_arg_t{}, std::current_exception());
+          }
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+        },
+        args_);
+  }
+
+  template <typename Result>
+  void resolve(Result&& result) {
+    if (result.is_empty()) {
+      loop();
+    } else if (result.is_value()) {
+      traits::unpack(std::move(promise_), std::forward<Result>(result));
+    } else {
+      assert(result.is_exception());
+      std::move(promise_).set_exception(
+          std::forward<Result>(result).get_exception());
+    }
+  }
+
+  void resolve(exception_arg_t, exception_t exception) {
+    promise_.set_exception(std::move(exception));
+  }
+};
+
+template <typename Promise, typename Callable, typename ArgsTuple>
+auto make_loop_frame(Promise&& promise, Callable&& callable,
+                     ArgsTuple&& args_tuple) {
+  using frame_t =
+      loop_frame<traits::unrefcv_t<Promise>, traits::unrefcv_t<Callable>,
+                 traits::unrefcv_t<ArgsTuple>>;
+
+  return std::make_shared<frame_t>(std::forward<Promise>(promise),
+                                   std::forward<Callable>(callable),
+                                   std::forward<ArgsTuple>(args_tuple));
+}
+
+template <typename Callable, typename... Args>
+auto loop(Callable&& callable, Args&&... args) {
+  using invocation_result_t =
+      decltype(util::invoke(callable, args...).finish());
+
+  auto constexpr hint = base::annotation_of(identify<invocation_result_t>{});
+
+  using trait_t = loop_trait<std::remove_const_t<decltype(hint)>>;
+
+  return trait_t::make([callable = std::forward<decltype(callable)>(callable),
+                        args = std::make_tuple(std::forward<decltype(args)>(
+                            args)...)](auto&& promise) mutable {
+    // Do the actual looping
+    auto frame = make_loop_frame(std::forward<decltype(promise)>(promise),
+                                 std::move(callable), std::move(args));
+    frame->loop();
+  });
+}
+
+template <typename Callable, typename Begin, typename End>
+auto make_range_looper(Callable&& callable, Begin&& begin, End&& end) {
+  return [callable = std::forward<Callable>(callable),
+          begin = std::forward<Begin>(begin),
+          end = std::forward<End>(end)]() mutable {
+    return util::invoke(callable, begin)
+        .then([&begin, &end]() mutable -> plain_t<result<>> {
+          // begin and end stays valid over the `then` here
+          if (++begin != end) {
+            return make_plain(result<>::empty());
+          } else {
+            return make_plain(make_result());
+          }
+        });
+  };
+}
+} // namespace operations
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_OPERATIONS_LOOP_HPP_INCLUDED

include/continuable/detail/operations/split.hpp

@@ -0,0 +1,118 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_OPERATIONS_SPLIT_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_OPERATIONS_SPLIT_HPP_INCLUDED
+
+#include <tuple>
+#include <utility>
+#include <continuable/continuable-base.hpp>
+#include <continuable/continuable-traverse.hpp>
+#include <continuable/continuable-types.hpp>
+#include <continuable/detail/utility/traits.hpp>
+
+namespace cti {
+namespace detail {
+namespace operations {
+template <typename T, bool Else, typename = void>
+struct operator_bool_or {
+  template <typename O>
+  static bool get(O&& /*obj*/) noexcept {
+    return Else;
+  }
+};
+template <typename T, bool Else>
+struct operator_bool_or<T, Else,
+                        traits::void_t<decltype(bool(std::declval<T&>()))>> {
+  template <typename O>
+  static bool get(O&& obj) noexcept {
+    return bool(obj);
+  }
+};
+
+template <typename First, typename... Promises>
+class split_promise {
+  First first_;
+  std::tuple<Promises...> promises_;
+
+public:
+  explicit split_promise(First first, Promises... promises)
+      : first_(std::move(first)), promises_(std::move(promises)...) {
+  }
+
+  template <typename... Args>
+  void operator()(Args&&... args) && {
+    traverse_pack(
+        [&](auto&& promise) mutable -> void {
+          using accessor =
+              operator_bool_or<traits::unrefcv_t<decltype(promise)>, true>;
+          if (accessor::get(promise)) {
+            std::forward<decltype(promise)>(promise)(args...);
+          }
+        },
+        std::move(promises_));
+
+    if (operator_bool_or<First, true>::get(first_)) {
+      std::move(first_)(std::forward<Args>(args)...);
+    }
+  }
+
+  template <typename... Args>
+  void set_value(Args... args) noexcept {
+    std::move (*this)(std::move(args)...);
+  }
+
+  void set_exception(exception_t error) noexcept {
+    std::move (*this)(exception_arg_t{}, std::move(error));
+  }
+
+  void set_canceled() noexcept {
+    std::move (*this)(exception_arg_t{}, exception_t{});
+  }
+
+  explicit operator bool() const noexcept {
+    bool is_valid = operator_bool_or<First, true>::get(first_);
+    traverse_pack(
+        [&](auto&& promise) mutable -> void {
+          using accessor =
+              operator_bool_or<traits::unrefcv_t<decltype(promise)>, true>;
+          if (!is_valid && accessor::get(promise)) {
+            is_valid = true;
+          }
+        },
+        promises_);
+    return is_valid;
+  }
+};
+} // namespace operations
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_OPERATIONS_SPLIT_HPP_INCLUDED

include/continuable/detail/other/coroutines.hpp

@@ -0,0 +1,273 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+// Exclude this header when coroutines are not available
+#ifndef CONTINUABLE_DETAIL_AWAITING_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_AWAITING_HPP_INCLUDED
+
+#include <cassert>
+#include <type_traits>
+#include <continuable/continuable-primitives.hpp>
+#include <continuable/continuable-result.hpp>
+#include <continuable/detail/core/annotation.hpp>
+#include <continuable/detail/core/base.hpp>
+#include <continuable/detail/core/types.hpp>
+#include <continuable/detail/features.hpp>
+#include <continuable/detail/utility/traits.hpp>
+#include <continuable/detail/utility/util.hpp>
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#  include <exception>
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+
+#if defined(CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE)
+#  include <experimental/coroutine>
+#elif defined(CONTINUABLE_HAS_COROUTINE)
+#  include <coroutine>
+#endif
+
+#if defined(CONTINUABLE_HAS_COROUTINE)
+namespace cti {
+namespace detail {
+namespace awaiting {
+/// We import the coroutine handle in our namespace
+#  if defined(CONTINUABLE_HAS_EXPERIMENTAL_COROUTINE)
+using std::experimental::coroutine_handle;
+using std::experimental::suspend_never;
+#  else
+using std::coroutine_handle;
+using std::suspend_never;
+#  endif
+
+#  if defined(CONTINUABLE_HAS_EXCEPTIONS)
+class await_canceled_exception : public std::exception {
+public:
+  await_canceled_exception() noexcept = default;
+
+  char const* what() const noexcept override {
+    return "co_await canceled due to cancellation of the continuation";
+  }
+};
+#  endif // CONTINUABLE_HAS_EXCEPTIONS
+
+template <typename T>
+struct result_from_identity;
+template <typename... T>
+struct result_from_identity<identity<T...>> {
+  using result_t = result<T...>;
+};
+
+/// An object which provides the internal buffer and helper methods
+/// for waiting on a continuable in a stackless coroutine.
+template <typename Continuable>
+class awaitable {
+  using hint_t = decltype(base::annotation_of(identify<Continuable>{}));
+  using result_t = typename result_from_identity<hint_t>::result_t;
+
+  /// The continuable which is invoked upon suspension
+  Continuable continuable_;
+  /// A cache which is used to pass the result of the continuation
+  /// to the coroutine.
+  result_t result_;
+  /// Enumeration that represents the suspension state of the awaitable.
+  enum class state : std::uint8_t {
+    suspended,
+    pending,
+    resolved,
+  };
+  /// An atomic that specifies whether the awaitable has suspended or not.
+  /// Allows to perform symmetric transfer on continuables that are
+  /// immediately resolved.
+  std::atomic<state> state_{state::pending};
+
+public:
+  explicit constexpr awaitable(Continuable&& continuable)
+    : continuable_(std::move(continuable)) {
+
+    // If the continuable is ready resolve the result from the
+    // continuable immediately.
+    if (base::attorney::is_ready(continuable_)) {
+      assert(result_.is_empty());
+      result_ = base::attorney::query(std::move(continuable_));
+    }
+  }
+
+  /// Return whether the continuable can provide its result instantly,
+  /// which also means its execution is side-effect free.
+  bool await_ready() const noexcept {
+    return !result_.is_empty();
+  }
+
+  /// Suspend the current context
+  // TODO Convert this to an r-value function once possible
+  bool await_suspend(coroutine_handle<> h) {
+    assert(result_.is_empty());
+    // Forward every result to the current awaitable
+    std::move(continuable_)
+        .next([h, this](auto&&... args) mutable {
+          assert(result_.is_empty());
+          result_ = result_t::from(std::forward<decltype(args)>(args)...);
+
+          // If true, it means that the promise was suspended (i.e., the
+          // awaitable await_suspend method has already returned). That
+          // means we must call the resume coroutine from the continuation
+          // chain.
+          if (state_.exchange(state::resolved, std::memory_order_acq_rel) ==
+              state::suspended) {
+            return h.resume();
+          }
+        })
+        .done();
+
+    return state_.exchange(state::suspended, std::memory_order_acq_rel) !=
+           state::resolved;
+  }
+
+  /// Resume the coroutine represented by the handle
+  typename result_t::value_t await_resume() noexcept(false) {
+    if (result_.is_value()) {
+      // When the result was resolved return it
+      return std::move(result_).get_value();
+    }
+
+    assert(result_.is_exception());
+
+#  if defined(CONTINUABLE_HAS_EXCEPTIONS)
+    if (exception_t e = result_.get_exception()) {
+      std::rethrow_exception(std::move(e));
+    } else {
+      throw await_canceled_exception();
+    }
+#  else  // CONTINUABLE_HAS_EXCEPTIONS
+    // Returning error types from co_await isn't supported!
+    CTI_DETAIL_TRAP();
+#  endif // CONTINUABLE_HAS_EXCEPTIONS
+  }
+};
+
+/// Converts a continuable into an awaitable object as described by
+/// the C++ coroutine TS.
+template <typename T>
+constexpr auto create_awaiter(T&& continuable) {
+  return awaitable<std::decay_t<T>>(std::forward<T>(continuable));
+}
+
+/// This makes it possible to take the coroutine_handle over on suspension
+struct handle_takeover {
+  coroutine_handle<>& handle_;
+
+  bool await_ready() noexcept {
+    return false;
+  }
+
+  void await_suspend(coroutine_handle<> handle) noexcept {
+    handle_ = handle;
+  }
+
+  void await_resume() noexcept {}
+};
+
+/// The type which is passed to the compiler that describes the properties
+/// of a continuable_base used as coroutine promise type.
+template <typename Continuable, typename Promise, typename... Args>
+struct promise_type;
+
+/// Implements the resolving method return_void and return_value accordingly
+template <typename Base>
+struct promise_resolver_base;
+
+template <typename Continuable, typename Promise>
+struct promise_resolver_base<promise_type<Continuable, Promise>> {
+  void return_void() {
+    auto me = static_cast<promise_type<Continuable, Promise>*>(this);
+    me->promise_.set_value();
+  }
+};
+template <typename Continuable, typename Promise, typename T>
+struct promise_resolver_base<promise_type<Continuable, Promise, T>> {
+  void return_value(T value) {
+    auto me = static_cast<promise_type<Continuable, Promise, T>*>(this);
+    me->promise_.set_value(std::move(value));
+  }
+};
+template <typename Continuable, typename Promise, typename... Args>
+struct promise_resolver_base<promise_type<Continuable, Promise, Args...>> {
+  template <typename T>
+  void return_value(T&& tuple_like) {
+    auto me = static_cast<promise_type<Continuable, Promise, Args...>*>(this);
+    traits::unpack(std::move(me->promise_), std::forward<T>(tuple_like));
+  }
+};
+
+template <typename Continuable, typename Promise, typename... Args>
+struct promise_type
+  : promise_resolver_base<promise_type<Continuable, Promise, Args...>> {
+
+  coroutine_handle<> handle_;
+  Promise promise_;
+
+  explicit promise_type() = default;
+
+  Continuable get_return_object() {
+    return [this](auto&& promise) {
+      promise_ = std::forward<decltype(promise)>(promise);
+      handle_.resume();
+    };
+  }
+
+  handle_takeover initial_suspend() {
+    return {handle_};
+  }
+
+  suspend_never final_suspend() noexcept {
+    return {};
+  }
+
+  void unhandled_exception() noexcept {
+#  if defined(CONTINUABLE_HAS_EXCEPTIONS)
+    try {
+      std::rethrow_exception(std::current_exception());
+    } catch (await_canceled_exception const&) {
+      promise_.set_canceled();
+    } catch (...) {
+      promise_.set_exception(std::current_exception());
+    }
+#  else  // CONTINUABLE_HAS_EXCEPTIONS
+    // Returning exception types from a coroutine isn't supported
+    CTI_DETAIL_TRAP();
+#  endif // CONTINUABLE_HAS_EXCEPTIONS
+  }
+};
+} // namespace awaiting
+} // namespace detail
+} // namespace cti
+#endif // defined(CONTINUABLE_HAS_COROUTINE)
+
+#endif // CONTINUABLE_DETAIL_UTIL_HPP_INCLUDED

include/continuable/detail/other/erasure.hpp

@@ -0,0 +1,241 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_ERASURE_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_ERASURE_HPP_INCLUDED
+
+#include <type_traits>
+#include <utility>
+#include <function2/function2.hpp>
+#include <continuable/detail/core/base.hpp>
+#include <continuable/detail/features.hpp>
+#include <continuable/detail/utility/traits.hpp>
+
+namespace cti {
+namespace detail {
+namespace erasure {
+template <typename... Args>
+using callback_erasure_t =
+    fu2::function_base<true, false, fu2::capacity_none, true, false,
+                       void(Args...)&&, void(exception_arg_t, exception_t) &&>;
+
+#ifdef CONTINUABLE_HAS_IMMEDIATE_TYPES
+template <typename... Args>
+using callback = callback_erasure_t<Args...>;
+#else
+template <typename... Args>
+class callback;
+
+template <typename T>
+struct is_callback : std::false_type {};
+template <typename... Args>
+struct is_callback<callback<Args...>> : std::true_type {};
+
+template <typename... Args>
+class callback : public callback_erasure_t<Args...> {
+public:
+  using erasure_t = callback_erasure_t<Args...>;
+  erasure_t erasure_;
+
+  callback() = default;
+  ~callback() = default;
+  callback(callback const&) = delete;
+  callback(callback&&) = default;
+  callback& operator=(callback const&) = delete;
+  callback& operator=(callback&&) = default;
+
+  template <
+      typename T,
+      std::enable_if_t<std::is_convertible<T, erasure_t>::value>* = nullptr,
+      std::enable_if_t<!is_callback<traits::unrefcv_t<T>>::value>* = nullptr>
+  /* implicit */ callback(T&& callable) : erasure_(std::forward<T>(callable)) {
+  }
+
+  template <
+      typename T,
+      std::enable_if_t<std::is_assignable<erasure_t, T>::value>* = nullptr,
+      std::enable_if_t<!is_callback<traits::unrefcv_t<T>>::value>* = nullptr>
+  callback& operator=(T&& callable) {
+    erasure_ = std::forward<T>(callable);
+    return *this;
+  }
+
+  void operator()(Args... args) && noexcept {
+    std::move(erasure_)(std::move(args)...);
+  }
+
+  void operator()(exception_arg_t exception_arg, exception_t exception) &&
+      noexcept {
+    std::move(erasure_)(exception_arg, std::move(exception));
+  }
+
+  explicit operator bool() const noexcept {
+    return bool(erasure_);
+  }
+};
+#endif
+
+using work_erasure_t =
+    fu2::function_base<true, false, fu2::capacity_fixed<32UL>, true, false,
+                       void()&&, void(exception_arg_t, exception_t) &&>;
+
+#ifdef CONTINUABLE_HAS_IMMEDIATE_TYPES
+using work = work_erasure_t;
+#else
+class work;
+
+template <typename T>
+struct is_work : std::false_type {};
+template <>
+struct is_work<work> : std::true_type {};
+
+class work {
+  using erasure_t = work_erasure_t;
+  erasure_t erasure_;
+
+public:
+  work() = default;
+  ~work() = default;
+  work(work const&) = delete;
+  work(work&&) = default;
+  work& operator=(work const&) = delete;
+  work& operator=(work&&) = default;
+
+  template <
+      typename T,
+      std::enable_if_t<std::is_convertible<T, erasure_t>::value>* = nullptr,
+      std::enable_if_t<!is_work<traits::unrefcv_t<T>>::value>* = nullptr>
+  /* implicit */ work(T&& callable) : erasure_(std::forward<T>(callable)) {
+  }
+
+  template <
+      typename T,
+      std::enable_if_t<std::is_assignable<erasure_t, T>::value>* = nullptr,
+      std::enable_if_t<!is_work<traits::unrefcv_t<T>>::value>* = nullptr>
+  work& operator=(T&& callable) {
+    erasure_ = std::forward<T>(callable);
+    return *this;
+  }
+
+  void operator()() && noexcept {
+    std::move(erasure_)();
+  }
+
+  void operator()(exception_arg_t, exception_t exception) && noexcept {
+    std::move(erasure_)(exception_arg_t{}, std::move(exception));
+  }
+
+  explicit operator bool() const noexcept {
+    return bool(erasure_);
+  }
+};
+#endif
+
+template <typename... Args>
+struct continuation_capacity {
+  using type = union {
+    void* pointer_;
+    base::ready_continuation<Args...> continuation_;
+  };
+
+  static constexpr std::size_t capacity = sizeof(type);
+  static constexpr std::size_t alignment = alignof(type);
+};
+
+template <typename... Args>
+using continuation_erasure_t = fu2::function_base<
+    true, false, continuation_capacity<Args...>, true, false,
+    void(promise_base<callback<Args...>, signature_arg_t<Args...>>),
+    bool(is_ready_arg_t) const, result<Args...>(unpack_arg_t)>;
+
+#ifdef CONTINUABLE_HAS_IMMEDIATE_TYPES
+template <typename... Args>
+using continuation = continuation_erasure_t<Args...>;
+#else
+template <typename... Args>
+class continuation;
+
+template <typename T>
+struct is_continuation : std::false_type {};
+template <typename... Args>
+struct is_continuation<continuation<Args...>> : std::true_type {};
+
+template <typename... Args>
+class continuation {
+  using erasure_t = continuation_erasure_t<Args...>;
+  erasure_t erasure_;
+
+public:
+  continuation() = default;
+  ~continuation() = default;
+  continuation(continuation const&) = delete;
+  continuation(continuation&&) = default;
+  continuation& operator=(continuation const&) = delete;
+  continuation& operator=(continuation&&) = default;
+
+  template <
+      typename T,
+      std::enable_if_t<std::is_convertible<T, erasure_t>::value>* = nullptr,
+      std::enable_if_t<!is_continuation<traits::unrefcv_t<T>>::value>* =
+          nullptr>
+  /* implicit */ continuation(T&& callable)
+      : erasure_(std::forward<T>(callable)) {
+  }
+
+  template <
+      typename T,
+      std::enable_if_t<std::is_assignable<erasure_t, T>::value>* = nullptr,
+      std::enable_if_t<!is_continuation<traits::unrefcv_t<T>>::value>* =
+          nullptr>
+  continuation& operator=(T&& callable) {
+    erasure_ = std::forward<T>(callable);
+    return *this;
+  }
+
+  void operator()(promise_base<callback<Args...>, //
+                               signature_arg_t<Args...>>
+                      promise) {
+    erasure_(std::move(promise));
+  }
+
+  bool operator()(is_ready_arg_t is_ready_arg) const {
+    return erasure_(is_ready_arg);
+  }
+
+  result<Args...> operator()(unpack_arg_t query_arg) {
+    return erasure_(query_arg);
+  }
+};
+#endif
+} // namespace erasure
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_ERASURE_HPP_INCLUDED

include/continuable/detail/other/promisify.hpp

@@ -0,0 +1,97 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_PROMISIFY_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_PROMISIFY_HPP_INCLUDED
+
+#include <type_traits>
+#include <continuable/continuable-base.hpp>
+#include <continuable/continuable-primitives.hpp>
+#include <continuable/detail/features.hpp>
+#include <continuable/detail/utility/traits.hpp>
+#include <continuable/detail/utility/util.hpp>
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#include <exception>
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+
+namespace cti {
+namespace detail {
+namespace convert {
+/// A resolver for promisifying asio and js style callbacks.
+inline auto default_resolver() {
+  return [](auto&& promise, auto&& e, auto&&... args) {
+    static_assert(
+        std::is_convertible<std::decay_t<decltype(e)>, exception_t>::value,
+        "The given error type must be convertible to the error type used! "
+        "Specify a custom resolver in order to apply a conversion to the "
+        "used error type.");
+
+    if (e) {
+      promise.set_exception(std::forward<decltype(e)>(e));
+    } else {
+      promise.set_value(std::forward<decltype(args)>(args)...);
+    }
+  };
+}
+
+template <typename... Result>
+struct promisify_helper {
+  template <typename Resolver, typename Callable, typename... Args>
+  static auto from(Resolver&& resolver, Callable&& callable, Args&&... args) {
+    return make_continuable<Result...>(
+        [resolver = std::forward<Resolver>(resolver),
+         args = traits::make_flat_tuple(std::forward<Callable>(callable),
+                                        std::forward<Args>(args)...)](
+            auto&& promise) mutable {
+          traits::unpack(
+              [promise = std::forward<decltype(promise)>(promise),
+               &resolver](auto&&... args) mutable {
+                // Call the resolver from with the promise and result
+                auto callback =
+                    [resolver = std::move(resolver),
+                     promise = std::move(promise)](auto&&... args) mutable {
+                      resolver(std::move(promise),
+                               std::forward<decltype(args)>(args)...);
+                    };
+
+                // Invoke the callback taking function
+                util::invoke(std::forward<decltype(args)>(args)...,
+                             std::move(callback));
+              },
+              std::move(args));
+        });
+  }
+};
+} // namespace convert
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_PROMISIFY_HPP_INCLUDED

include/continuable/detail/other/testing.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -33,13 +33,12 @@
 
 #include <type_traits>
 #include <utility>
-
 #include <gtest/gtest.h>
-
+#include <continuable/continuable-primitives.hpp>
+#include <continuable/detail/core/types.hpp>
 #include <continuable/detail/features.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/types.hpp>
+#include <continuable/detail/utility/util.hpp>
-#include <continuable/detail/util.hpp>
 
 namespace cti {
 namespace detail {
@@ -55,7 +54,7 @@ void assert_async_completion(C&& continuable) {
         // Workaround for our known GCC bug.
         util::unused(std::forward<decltype(args)>(args)...);
       })
-      .fail([](cti::error_type /*error*/) {
+      .fail([](cti::exception_t /*error*/) {
         // ...
         FAIL();
       });
@@ -74,7 +73,28 @@ void assert_async_exception_completion(C&& continuable) {
         // ...
         FAIL();
       })
-      .fail([called](cti::error_type /*error*/) {
+      .fail([called](cti::exception_t error) {
+        ASSERT_TRUE(bool(error));
+        ASSERT_FALSE(*called);
+        *called = true;
+      });
+
+  ASSERT_TRUE(*called);
+}
+
+template <typename C>
+void assert_async_cancellation(C&& continuable) {
+  auto called = std::make_shared<bool>(false);
+  std::forward<C>(continuable)
+      .then([](auto&&... args) {
+        // Workaround for our known GCC bug.
+        util::unused(std::forward<decltype(args)>(args)...);
+
+        // ...
+        FAIL();
+      })
+      .fail([called](cti::exception_t error) {
+        ASSERT_FALSE(bool(error));
         ASSERT_FALSE(*called);
         *called = true;
       });
@@ -91,7 +111,7 @@ void assert_async_never_completed(C&& continuable) {
 
         FAIL();
       })
-      .fail([](cti::error_type /*error*/) {
+      .fail([](cti::exception_t) {
         // ...
         FAIL();
       });
@@ -101,11 +121,10 @@ template <typename C, typename V>
 void assert_async_validation(C&& continuable, V&& validator) {
   assert_async_completion(
       std::forward<C>(continuable)
-          .then([validator =
+          .then(
-                     std::forward<V>(validator)](auto&&... args) mutable {
+              [validator = std::forward<V>(validator)](auto&&... args) mutable {
-
+                validator(std::forward<decltype(args)>(args)...);
-            validator(std::forward<decltype(args)>(args)...);
+              }));
-          }));
 }
 
 /// Expects that the continuable is finished with the given arguments
@@ -115,18 +134,17 @@ void assert_async_binary_validation(V&& validator, C&& continuable,
 
   using size = std::integral_constant<std::size_t, sizeof...(expected)>;
 
-  assert_async_validation(std::forward<C>(continuable), [
+  assert_async_validation(
-    expected_pack = std::make_tuple(std::forward<Args>(expected)...),
+      std::forward<C>(continuable),
-    validator = std::forward<V>(validator)
+      [expected_pack = std::make_tuple(std::forward<Args>(expected)...),
-  ](auto&&... args) mutable {
+       validator = std::forward<V>(validator)](auto&&... args) mutable {
+        static_assert(size::value == sizeof...(args),
+                      "Async completion handler called with a different count "
+                      "of arguments!");
 
-    static_assert(size::value == sizeof...(args),
+        validator(std::make_tuple(std::forward<decltype(args)>(args)...),
-                  "Async completion handler called with a different count "
+                  expected_pack);
-                  "of arguments!");
+      });
-
-    validator(std::make_tuple(std::forward<decltype(args)>(args)...),
-              expected_pack);
-  });
 }
 
 /// Expects that the continuable is finished with the given arguments
@@ -139,20 +157,19 @@ void assert_async_binary_exception_validation(V&& validator, C&& continuable,
         // Workaround for our known GCC bug.
         util::unused(std::forward<decltype(args)>(args)...);
 
-        // ...
+        // The exception was not thrown!
         FAIL();
       })
-      .fail([
+      .fail([called, validator = std::forward<decltype(validator)>(validator),
-        called, validator = std::forward<decltype(validator)>(validator),
+             expected = std::forward<decltype(expected)>(expected)](
-        expected = std::forward<decltype(expected)>(expected)
+                exception_t error) {
-      ](types::error_type error) {
         ASSERT_FALSE(*called);
         *called = true;
 
 #if defined(CONTINUABLE_HAS_EXCEPTIONS)
         try {
           std::rethrow_exception(error);
-        } catch (std::decay_t<decltype(expected)>& exception) {
+        } catch (std::decay_t<decltype(expected)> const& exception) {
           validator(exception, expected);
         } catch (...) {
           FAIL();
@@ -183,15 +200,14 @@ template <typename... Expected>
 struct assert_async_types_validator {
   template <typename... Actual>
   void operator()(Actual...) {
-    static_assert(std::is_same<traits::identity<Actual...>,
+    static_assert(
-                               traits::identity<Expected...>>::value,
+        std::is_same<identity<Actual...>, identity<Expected...>>::value,
-                  "The called arguments don't match with the expected ones!");
+        "The called arguments don't match with the expected ones!");
   }
 };
 
 template <typename C, typename... Args>
-void assert_async_types(C&& continuable,
+void assert_async_types(C&& continuable, identity<Args...> /*expected*/) {
-                        traits::identity<Args...> /*expected*/) {
   assert_async_validation(std::forward<C>(continuable),
                           assert_async_types_validator<Args...>{});
 }

include/continuable/detail/promisify.hpp

@@ -1,95 +0,0 @@
-
-/*
-
-                        /~` _  _ _|_. _     _ |_ | _
-                        \_,(_)| | | || ||_|(_||_)|(/_
-
-                    https://github.com/Naios/continuable
-                                   v3.0.0
-
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
-
-  Permission is hereby granted, free of charge, to any person obtaining a copy
-  of this software and associated documentation files(the "Software"), to deal
-  in the Software without restriction, including without limitation the rights
-  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
-  copies of the Software, and to permit persons to whom the Software is
-  furnished to do so, subject to the following conditions :
-
-  The above copyright notice and this permission notice shall be included in
-  all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
-  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-  SOFTWARE.
-**/
-
-#ifndef CONTINUABLE_DETAIL_PROMISIFY_HPP_INCLUDED
-#define CONTINUABLE_DETAIL_PROMISIFY_HPP_INCLUDED
-
-#include <type_traits>
-
-#if defined(CONTINUABLE_HAS_EXCEPTIONS)
-#include <exception>
-#endif // CONTINUABLE_HAS_EXCEPTIONS
-
-#include <continuable/continuable-base.hpp>
-#include <continuable/detail/traits.hpp>
-#include <continuable/detail/util.hpp>
-
-namespace cti {
-namespace detail {
-namespace convert {
-/// A helper class for promisifying asio and js style callback
-/// taking functions into a continuable.
-template <typename P>
-struct promisify_default {
-  P promise;
-
-  template <typename E, typename... T>
-  void operator()(E&& error, T&&... result) {
-    if (error) {
-#if defined(CONTINUABLE_HAS_EXCEPTIONS)
-      promise.set_exception(std::make_exception_ptr(std::forward<E>(error)));
-#else
-      promise.set_exception(
-          std::error_condition(error.value(), error.category()));
-#endif // CONTINUABLE_HAS_EXCEPTIONS
-
-    } else {
-      promise.set_value(std::forward<T>(result)...);
-    }
-  }
-};
-
-template <typename... Result>
-struct promisify_helper {
-  template <template <class T> class Evaluator, typename Callable,
-            typename... Args>
-  static auto from(Callable&& callable, Args&&... args) {
-    return make_continuable<Result...>([args = std::make_tuple(
-                                            std::forward<Callable>(callable),
-                                            std::forward<Args>(args)...)](
-        auto&& promise) mutable {
-
-      traits::unpack(
-          std::move(args), [promise = std::forward<decltype(promise)>(promise)](
-                               auto&&... args) mutable {
-            Evaluator<std::decay_t<decltype(promise)>> evaluator{
-                std::move(promise)};
-
-            util::invoke(std::forward<decltype(args)>(args)...,
-                         std::move(evaluator));
-          });
-    });
-  }
-};
-} // namespace convert
-} // namespace detail
-} // namespace cti
-
-#endif // CONTINUABLE_DETAIL_PROMISIFY_HPP_INCLUDED

include/continuable/detail/traits.hpp

@@ -1,358 +0,0 @@
-
-/*
-
-                        /~` _  _ _|_. _     _ |_ | _
-                        \_,(_)| | | || ||_|(_||_)|(/_
-
-                    https://github.com/Naios/continuable
-                                   v3.0.0
-
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
-
-  Permission is hereby granted, free of charge, to any person obtaining a copy
-  of this software and associated documentation files(the "Software"), to deal
-  in the Software without restriction, including without limitation the rights
-  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
-  copies of the Software, and to permit persons to whom the Software is
-  furnished to do so, subject to the following conditions :
-
-  The above copyright notice and this permission notice shall be included in
-  all copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
-  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-  SOFTWARE.
-**/
-
-#ifndef CONTINUABLE_DETAIL_TRAITS_HPP_INCLUDED
-#define CONTINUABLE_DETAIL_TRAITS_HPP_INCLUDED
-
-#include <cstdint>
-#include <initializer_list>
-#include <tuple>
-#include <type_traits>
-#include <utility>
-
-#include <continuable/detail/features.hpp>
-
-namespace cti {
-namespace detail {
-namespace traits {
-/// Evaluates to the element at position I.
-template <std::size_t I, typename... Args>
-using at_t = decltype(std::get<I>(std::declval<std::tuple<Args...>>()));
-
-namespace detail {
-template <typename T, typename... Args>
-struct index_of_impl;
-template <typename T, typename... Args>
-struct index_of_impl<T, T, Args...> : std::integral_constant<std::size_t, 0U> {
-};
-template <typename T, typename U, typename... Args>
-struct index_of_impl<T, U, Args...>
-    : std::integral_constant<std::size_t,
-                             1 + index_of_impl<T, Args...>::value> {};
-} // namespace detail
-
-/// Evaluates to the index of T in the given pack
-template <typename T, typename... Args>
-using index_of_t = detail::index_of_impl<T, Args...>;
-
-/// A tagging type for wrapping other types
-template <typename... T>
-struct identity {};
-template <typename T>
-struct identity<T> : std::common_type<T> {};
-
-template <typename>
-struct is_identity : std::false_type {};
-template <typename... Args>
-struct is_identity<identity<Args...>> : std::true_type {};
-
-template <typename T>
-constexpr identity<std::decay_t<T>> identity_of(T const& /*type*/) noexcept {
-  return {};
-}
-template <typename... Args>
-constexpr identity<Args...> identity_of(identity<Args...> /*type*/) noexcept {
-  return {};
-}
-template <typename T>
-using identify = std::conditional_t<is_identity<std::decay_t<T>>::value, T,
-                                    identity<std::decay_t<T>>>;
-
-template <std::size_t I, typename... T>
-constexpr auto get(identity<T...>) noexcept {
-  return identify<at_t<I, T...>>{};
-}
-
-namespace detail {
-// Equivalent to C++17's std::void_t which targets a bug in GCC,
-// that prevents correct SFINAE behavior.
-// See http://stackoverflow.com/questions/35753920 for details.
-template <typename...>
-struct deduce_to_void : std::common_type<void> {};
-} // namespace detail
-
-/// C++17 like void_t type
-template <typename... T>
-using void_t = typename detail::deduce_to_void<T...>::type;
-
-namespace detail {
-template <typename Type, typename TrueCallback>
-constexpr void static_if_impl(std::true_type, Type&& type,
-                              TrueCallback&& trueCallback) {
-  std::forward<TrueCallback>(trueCallback)(std::forward<Type>(type));
-}
-
-template <typename Type, typename TrueCallback>
-constexpr void static_if_impl(std::false_type, Type&& /*type*/,
-                              TrueCallback&& /*trueCallback*/) {
-}
-
-template <typename Type, typename TrueCallback, typename FalseCallback>
-constexpr auto static_if_impl(std::true_type, Type&& type,
-                              TrueCallback&& trueCallback,
-                              FalseCallback&& /*falseCallback*/) {
-  return std::forward<TrueCallback>(trueCallback)(std::forward<Type>(type));
-}
-
-template <typename Type, typename TrueCallback, typename FalseCallback>
-constexpr auto static_if_impl(std::false_type, Type&& type,
-                              TrueCallback&& /*trueCallback*/,
-                              FalseCallback&& falseCallback) {
-  return std::forward<FalseCallback>(falseCallback)(std::forward<Type>(type));
-}
-
-/// Evaluates to the size of the given tuple like type,
-// / if the type has no static size it will be one.
-template <typename T, typename Enable = void>
-struct tuple_like_size : std::integral_constant<std::size_t, 1U> {};
-template <typename T>
-struct tuple_like_size<T, void_t<decltype(std::tuple_size<T>::value)>>
-    : std::tuple_size<T> {};
-} // namespace detail
-
-/// Returns the pack size of the given empty pack
-constexpr std::size_t pack_size_of(identity<>) noexcept {
-  return 0U;
-}
-/// Returns the pack size of the given type
-template <typename T>
-constexpr std::size_t pack_size_of(identity<T>) noexcept {
-  return detail::tuple_like_size<T>::value;
-}
-/// Returns the pack size of the given type
-template <typename First, typename Second, typename... Args>
-constexpr std::size_t pack_size_of(identity<First, Second, Args...>) noexcept {
-  return 2U + sizeof...(Args);
-}
-
-/// Returns an index sequence of the given type
-template <typename T>
-constexpr auto sequence_of(identity<T>) noexcept {
-  constexpr auto const size = pack_size_of(identity<T>{});
-  return std::make_index_sequence<size>();
-}
-
-/// Invokes the callback only if the given type matches the check
-template <typename Type, typename Check, typename TrueCallback>
-constexpr void static_if(Type&& type, Check&& check,
-                         TrueCallback&& trueCallback) {
-  detail::static_if_impl(std::forward<Check>(check)(type),
-                         std::forward<Type>(type),
-                         std::forward<TrueCallback>(trueCallback));
-}
-
-/// Invokes the callback only if the given type matches the check
-template <typename Type, typename Check, typename TrueCallback,
-          typename FalseCallback>
-constexpr auto static_if(Type&& type, Check&& check,
-                         TrueCallback&& trueCallback,
-                         FalseCallback&& falseCallback) {
-  return detail::static_if_impl(std::forward<Check>(check)(type),
-                                std::forward<Type>(type),
-                                std::forward<TrueCallback>(trueCallback),
-                                std::forward<FalseCallback>(falseCallback));
-}
-
-/// Calls the given unpacker with the content of the given sequence
-template <typename U, std::size_t... I>
-constexpr decltype(auto) unpack(std::integer_sequence<std::size_t, I...>,
-                                U&& unpacker) {
-  return std::forward<U>(unpacker)(std::integral_constant<std::size_t, I>{}...);
-}
-
-/// Calls the given unpacker with the content of the given sequenceable
-template <typename F, typename U, std::size_t... I>
-constexpr auto unpack(F&& first_sequenceable, U&& unpacker,
-                      std::integer_sequence<std::size_t, I...>)
-    -> decltype(std::forward<U>(unpacker)(
-        get<I>(std::forward<F>(first_sequenceable))...)) {
-  (void)first_sequenceable;
-  return std::forward<U>(unpacker)(
-      get<I>(std::forward<F>(first_sequenceable))...);
-}
-/// Calls the given unpacker with the content of the given sequenceable
-template <typename F, typename S, typename U, std::size_t... If,
-          std::size_t... Is>
-constexpr auto unpack(F&& first_sequenceable, S&& second_sequenceable,
-                      U&& unpacker, std::integer_sequence<std::size_t, If...>,
-                      std::integer_sequence<std::size_t, Is...>)
-    -> decltype(std::forward<U>(unpacker)(
-        get<If>(std::forward<F>(first_sequenceable))...,
-        get<Is>(std::forward<S>(second_sequenceable))...)) {
-  (void)first_sequenceable;
-  (void)second_sequenceable;
-  return std::forward<U>(unpacker)(
-      get<If>(std::forward<F>(first_sequenceable))...,
-      get<Is>(std::forward<S>(second_sequenceable))...);
-}
-/// Calls the given unpacker with the content of the given sequenceable
-template <typename F, typename U>
-constexpr auto unpack(F&& first_sequenceable, U&& unpacker)
-    -> decltype(unpack(std::forward<F>(first_sequenceable),
-                       std::forward<U>(unpacker),
-                       sequence_of(identify<decltype(first_sequenceable)>{}))) {
-  return unpack(std::forward<F>(first_sequenceable), std::forward<U>(unpacker),
-                sequence_of(identify<decltype(first_sequenceable)>{}));
-}
-/// Calls the given unpacker with the content of the given sequenceables
-template <typename F, typename S, typename U>
-constexpr auto unpack(F&& first_sequenceable, S&& second_sequenceable,
-                      U&& unpacker)
-    -> decltype(unpack(std::forward<F>(first_sequenceable),
-                       std::forward<S>(second_sequenceable),
-                       std::forward<U>(unpacker),
-                       sequence_of(identity_of(first_sequenceable)),
-                       sequence_of(identity_of(second_sequenceable)))) {
-  return unpack(std::forward<F>(first_sequenceable),
-                std::forward<S>(second_sequenceable), std::forward<U>(unpacker),
-                sequence_of(identity_of(first_sequenceable)),
-                sequence_of(identity_of(second_sequenceable)));
-}
-
-/// Adds the given type at the back of the left sequenceable
-template <typename Left, typename Element>
-constexpr auto push(Left&& left, Element&& element) {
-  return unpack(std::forward<Left>(left), [&](auto&&... args) {
-    return std::make_tuple(std::forward<decltype(args)>(args)...,
-                           std::forward<Element>(element));
-  });
-}
-
-/// Adds the element to the back of the identity
-template <typename... Args, typename Element>
-constexpr auto push(identity<Args...>, identity<Element>) noexcept {
-  return identity<Args..., Element>{};
-}
-
-/// Removes the first element from the identity
-template <typename First, typename... Rest>
-constexpr auto pop_first(identity<First, Rest...>) noexcept {
-  return identity<Rest...>{};
-}
-
-/// Returns the merged sequence
-template <typename Left>
-constexpr auto merge(Left&& left) {
-  return std::forward<Left>(left);
-}
-/// Merges the left sequenceable with the right ones
-template <typename Left, typename Right, typename... Rest>
-constexpr auto merge(Left&& left, Right&& right, Rest&&... rest) {
-  // Merge the left with the right sequenceable and
-  // merge the result with the rest.
-  return merge(unpack(std::forward<Left>(left), std::forward<Right>(right),
-                      [&](auto&&... args) {
-                        // Maybe use: template <template<typename...> class T,
-                        // typename... Args>
-                        return std::make_tuple(
-                            std::forward<decltype(args)>(args)...);
-                      }),
-               std::forward<Rest>(rest)...);
-}
-/// Merges the left identity with the right ones
-template <typename... LeftArgs, typename... RightArgs, typename... Rest>
-constexpr auto merge(identity<LeftArgs...> /*left*/,
-                     identity<RightArgs...> /*right*/, Rest&&... rest) {
-  return merge(identity<LeftArgs..., RightArgs...>{},
-               std::forward<Rest>(rest)...);
-}
-
-namespace detail {
-template <typename T, typename Args, typename = traits::void_t<>>
-struct is_invokable_impl : std::common_type<std::false_type> {};
-
-template <typename T, typename... Args>
-struct is_invokable_impl<
-    T, std::tuple<Args...>,
-    void_t<decltype(std::declval<T>()(std::declval<Args>()...))>>
-    : std::common_type<std::true_type> {};
-} // namespace detail
-
-/// Deduces to a std::true_type if the given type is callable with the arguments
-/// inside the given tuple.
-/// The main reason for implementing it with the detection idiom instead of
-/// hana like detection is that MSVC has issues with capturing raw template
-/// arguments inside lambda closures.
-///
-/// ```cpp
-/// traits::is_invokable<object, std::tuple<Args...>>
-/// ```
-template <typename T, typename Args>
-using is_invokable_from_tuple =
-    typename detail::is_invokable_impl<T, Args>::type;
-
-// Checks whether the given callable object is invocable with the given
-// arguments. This doesn't take member functions into account!
-template <typename T, typename... Args>
-using is_invocable = is_invokable_from_tuple<T, std::tuple<Args...>>;
-
-/// Deduces to a std::false_type
-template <typename T>
-using fail = std::integral_constant<bool, !std::is_same<T, T>::value>;
-
-#ifdef CONTINUABLE_HAS_CXX17_DISJUNCTION
-using std::disjunction;
-#else
-namespace detail {
-/// Declares a C++14 polyfill for C++17 std::disjunction.
-template <typename Args, typename = void_t<>>
-struct disjunction_impl : std::common_type<std::true_type> {};
-template <typename... Args>
-struct disjunction_impl<identity<Args...>,
-                        void_t<std::enable_if_t<!bool(Args::value)>...>>
-    : std::common_type<std::false_type> {};
-} // namespace detail
-
-template <typename... Args>
-using disjunction = typename detail::disjunction_impl<identity<Args...>>::type;
-#endif // CONTINUABLE_HAS_CXX17_DISJUNCTION
-
-#ifdef CONTINUABLE_HAS_CXX17_CONJUNCTION
-using std::conjunction;
-#else
-namespace detail {
-/// Declares a C++14 polyfill for C++17 std::conjunction.
-template <typename Args, typename = void_t<>>
-struct conjunction_impl : std::common_type<std::false_type> {};
-template <typename... Args>
-struct conjunction_impl<identity<Args...>,
-                        void_t<std::enable_if_t<bool(Args::value)>...>>
-    : std::common_type<std::true_type> {};
-} // namespace detail
-
-template <typename... Args>
-using conjunction = typename detail::conjunction_impl<identity<Args...>>::type;
-#endif // CONTINUABLE_HAS_CXX17_CONJUNCTION
-
-} // namespace traits
-} // namespace detail
-} // namespace cti
-
-#endif // CONTINUABLE_DETAIL_TRAITS_HPP_INCLUDED

include/continuable/detail/transforms/future.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,23 +21,23 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   SOFTWARE.
 **/
 
-#ifndef CONTINUABLE_DETAIL_TRANSFORMS_HPP_INCLUDED
+#ifndef CONTINUABLE_DETAIL_TRANSFORMS_FUTURE_HPP_INCLUDED
-#define CONTINUABLE_DETAIL_TRANSFORMS_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_TRANSFORMS_FUTURE_HPP_INCLUDED
 
 #include <future>
-
+#include <continuable/continuable-primitives.hpp>
-#include <continuable/detail/base.hpp>
+#include <continuable/detail/core/annotation.hpp>
+#include <continuable/detail/core/base.hpp>
+#include <continuable/detail/core/types.hpp>
 #include <continuable/detail/features.hpp>
-#include <continuable/detail/hints.hpp>
+#include <continuable/detail/utility/util.hpp>
-#include <continuable/detail/types.hpp>
-#include <continuable/detail/util.hpp>
 
 namespace cti {
 namespace detail {
@@ -77,8 +77,7 @@ template <typename Hint>
 class promise_callback;
 
 template <typename... Args>
-class promise_callback<hints::signature_hint_tag<Args...>>
+class promise_callback<identity<Args...>> : public future_trait<Args...> {
-    : public future_trait<Args...> {
 
   typename future_trait<Args...>::promise_t promise_;
 
@@ -95,7 +94,7 @@ public:
   }
 
   /// Resolves the promise through the exception
-  void operator()(types::dispatch_error_tag, types::error_type error) {
+  void operator()(exception_arg_t, exception_t error) {
 #if defined(CONTINUABLE_HAS_EXCEPTIONS)
     promise_.set_exception(error);
 #else
@@ -104,7 +103,7 @@ public:
     // Can't forward a std::error_condition or custom error type
     // to a std::promise. Handle the error first in order
     // to prevent this trap!
-    util::trap();
+    CTI_DETAIL_TRAP();
 #endif // CONTINUABLE_HAS_EXCEPTIONS
   }
 
@@ -116,10 +115,10 @@ public:
 
 /// Transforms the continuation to a future
 template <typename Data, typename Annotation>
-auto as_future(continuable_base<Data, Annotation>&& continuable) {
+auto to_future(continuable_base<Data, Annotation>&& continuable) {
   // Create the promise which is able to supply the current arguments
   constexpr auto const hint =
-      hints::hint_of(traits::identify<decltype(continuable)>{});
+      base::annotation_of(identify<decltype(continuable)>{});
 
   promise_callback<std::decay_t<decltype(hint)>> callback;
   (void)hint;
@@ -136,4 +135,4 @@ auto as_future(continuable_base<Data, Annotation>&& continuable) {
 } // namespace detail
 } // namespace cti
 
-#endif // CONTINUABLE_DETAIL_TRANSFORMS_HPP_INCLUDED
+#endif // CONTINUABLE_DETAIL_TRANSFORMS_FUTURE_HPP_INCLUDED

include/continuable/detail/transforms/wait.hpp

@@ -0,0 +1,264 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_TRANSFORMS_WAIT_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_TRANSFORMS_WAIT_HPP_INCLUDED
+
+#include <atomic>
+#include <cassert>
+#include <condition_variable>
+#include <memory>
+#include <mutex>
+#include <continuable/continuable-primitives.hpp>
+#include <continuable/continuable-result.hpp>
+#include <continuable/detail/core/annotation.hpp>
+#include <continuable/detail/core/base.hpp>
+#include <continuable/detail/core/types.hpp>
+#include <continuable/detail/features.hpp>
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+#  include <exception>
+#endif
+
+namespace cti {
+namespace detail {
+namespace transforms {
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+class wait_transform_canceled_exception : public std::exception {
+public:
+  wait_transform_canceled_exception() noexcept = default;
+
+  char const* what() const noexcept override {
+    return "cti::transforms::wait canceled due to cancellation of the "
+           "continuation";
+  }
+};
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+
+template <typename Hint>
+struct sync_trait;
+template <typename... Args>
+struct sync_trait<identity<Args...>> {
+  using result_t = result<Args...>;
+};
+
+using lock_t = std::unique_lock<std::mutex>;
+using condition_variable_t = std::condition_variable;
+
+template <typename Result>
+struct unsafe_unlocker {
+  explicit unsafe_unlocker(std::atomic_bool* ready, condition_variable_t* cv,
+                           std::mutex* mutex, Result* result)
+    : ready_(ready)
+    , cv_(cv)
+    , mutex_(mutex)
+    , result_(result) {}
+
+  unsafe_unlocker(unsafe_unlocker const&) = delete;
+  unsafe_unlocker(unsafe_unlocker&&) = default;
+  unsafe_unlocker& operator=(unsafe_unlocker const&) = delete;
+  unsafe_unlocker& operator=(unsafe_unlocker&&) = default;
+
+  ~unsafe_unlocker() {
+    unlock(Result::empty());
+  }
+
+  template <typename... Args>
+  void operator()(Args&&... args) {
+    unlock(Result::from(std::forward<Args>(args)...));
+  }
+
+  void unlock(Result&& result) {
+    if (!ownership_.is_acquired()) {
+      return;
+    }
+    ownership_.release();
+
+    lock_t lock(*mutex_);
+
+    *result_ = std::move(result);
+
+    assert(!ready_->load(std::memory_order_acquire));
+    ready_->store(true, std::memory_order_release);
+
+    cv_->notify_all();
+  }
+
+  std::atomic_bool* ready_;
+  condition_variable_t* cv_;
+  std::mutex* mutex_;
+  Result* result_;
+  util::ownership ownership_;
+};
+
+template <typename Data, typename Annotation,
+          typename Result = typename sync_trait<Annotation>::result_t>
+Result wait_relaxed(continuable_base<Data, Annotation>&& continuable) {
+
+  // Do an immediate unpack if the continuable is ready
+  if (continuable.is_ready()) {
+    return std::move(continuable).unpack();
+  }
+
+  condition_variable_t cv;
+  std::mutex cv_mutex;
+
+  std::atomic_bool ready{false};
+  Result sync_result;
+
+  std::move(continuable)
+      .next(unsafe_unlocker<Result>{
+          &ready,
+          &cv,
+          &cv_mutex,
+          &sync_result,
+      })
+      .done();
+
+  lock_t lock(cv_mutex);
+  if (!ready.load(std::memory_order_acquire)) {
+    cv.wait(lock, [&] {
+      return ready.load(std::memory_order_acquire);
+    });
+  }
+
+  return sync_result;
+}
+
+/// Transforms the continuation to sync execution and unpacks the result the if
+/// possible
+template <typename Data, typename Annotation>
+auto wait_and_unpack(continuable_base<Data, Annotation>&& continuable) {
+
+  auto sync_result = wait_relaxed(std::move(continuable));
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+  if (sync_result.is_value()) {
+    return std::move(sync_result).get_value();
+  } else if (sync_result.is_exception()) {
+    if (sync_result.is_exception()) {
+      if (exception_t e = sync_result.get_exception()) {
+        std::rethrow_exception(e);
+      }
+    }
+  }
+
+  throw wait_transform_canceled_exception();
+#else
+  return sync_result;
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+}
+
+template <typename Result>
+struct wait_frame {
+  std::mutex cv_mutex;
+  std::mutex rw_mutex;
+  condition_variable_t cv;
+  std::atomic_bool ready{false};
+  Result sync_result;
+};
+
+template <typename Result>
+struct unlocker {
+  unlocker(unlocker const&) = delete;
+  unlocker(unlocker&&) = default;
+  unlocker& operator=(unlocker const&) = delete;
+  unlocker& operator=(unlocker&&) = default;
+
+  explicit unlocker(std::weak_ptr<wait_frame<Result>> frame)
+    : frame_(std::move(frame)) {}
+
+  ~unlocker() {
+    unlock(Result::empty());
+  }
+
+  template <typename... Args>
+  void operator()(Args&&... args) {
+    unlock(Result::from(std::forward<decltype(args)>(args)...));
+  }
+
+  void unlock(Result&& result) {
+    if (!ownership_.is_acquired()) {
+      return;
+    }
+    ownership_.release();
+
+    if (auto locked = frame_.lock()) {
+      {
+        std::lock_guard<std::mutex> rw_lock(locked->rw_mutex);
+        assert(!locked->ready.load(std::memory_order_acquire));
+        locked->sync_result = std::move(result);
+      }
+
+      locked->ready.store(true, std::memory_order_release);
+      locked->cv.notify_all();
+    }
+  }
+
+  std::weak_ptr<wait_frame<Result>> frame_;
+  util::ownership ownership_;
+};
+
+template <typename Data, typename Annotation, typename Waiter,
+          typename Result = typename sync_trait<Annotation>::result_t>
+Result wait_unsafe(continuable_base<Data, Annotation>&& continuable,
+                   Waiter&& waiter) {
+
+  // Do an immediate unpack if the continuable is ready
+  if (continuable.is_ready()) {
+    return std::move(continuable).unpack();
+  }
+
+  using frame_t = wait_frame<Result>;
+
+  auto frame = std::make_shared<frame_t>();
+
+  std::move(continuable)
+      .next(unlocker<Result>{std::weak_ptr<frame_t>(frame)})
+      .done();
+
+  if (!frame->ready.load(std::memory_order_acquire)) {
+    lock_t lock(frame->cv_mutex);
+    std::forward<Waiter>(waiter)(frame->cv, lock, [&] {
+      return frame->ready.load(std::memory_order_acquire);
+    });
+  }
+
+  return ([&] {
+    std::lock_guard<std::mutex> rw_lock(frame->rw_mutex);
+    Result cached = std::move(frame->sync_result);
+    return cached;
+  })();
+}
+} // namespace transforms
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_TRANSFORMS_WAIT_HPP_INCLUDED

include/continuable/detail/traversal/container-category.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -33,8 +33,7 @@
 
 #include <tuple>
 #include <type_traits>
-
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/traits.hpp>
 
 namespace cti {
 namespace detail {

include/continuable/detail/traversal/range.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -35,8 +35,7 @@
 #include <type_traits>
 #include <utility>
 #include <vector>
-
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/traits.hpp>
 
 namespace cti {
 namespace detail {

include/continuable/detail/traversal/traverse-async.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -39,9 +39,8 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/detail/traversal/container-category.hpp>
-#include <continuable/detail/container-category.hpp>
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/traits.hpp>
 
 namespace cti {
 namespace detail {
@@ -98,10 +97,8 @@ public:
 /// given iterator tuple.
 template <typename Frame, typename State>
 auto make_resume_traversal_callable(Frame&& frame, State&& state)
-    -> resume_traversal_callable<typename std::decay<Frame>::type,
+    -> resume_traversal_callable<std::decay_t<Frame>, std::decay_t<State>> {
-                                 typename std::decay<State>::type> {
+  return resume_traversal_callable<std::decay_t<Frame>, std::decay_t<State>>(
-  return resume_traversal_callable<typename std::decay<Frame>::type,
-                                   typename std::decay<State>::type>(
       std::forward<Frame>(frame), std::forward<State>(state));
 }
 
@@ -231,7 +228,8 @@ struct static_async_range {
   }
 
   template <std::size_t Position>
-  constexpr auto relocate() const noexcept {
+  constexpr auto relocate(std::integral_constant<std::size_t, Position>) const
+      noexcept {
     return static_async_range<Target, Position, End>{target_};
   }
 
@@ -291,9 +289,9 @@ struct dynamic_async_range {
 };
 
 template <typename T>
-using dynamic_async_range_of_t = dynamic_async_range<
+using dynamic_async_range_of_t =
-    typename std::decay<decltype(std::begin(std::declval<T>()))>::type,
+    dynamic_async_range<std::decay_t<decltype(std::begin(std::declval<T>()))>,
-    typename std::decay<decltype(std::end(std::declval<T>()))>::type>;
+                        std::decay_t<decltype(std::end(std::declval<T>()))>>;
 
 /// Returns a dynamic range for the given type
 template <typename T>
@@ -337,9 +335,8 @@ public:
     auto hierarchy = std::tuple_cat(
         std::make_tuple(std::forward<Parent>(parent)), hierarchy_);
 
-    return async_traversal_point<Frame, typename std::decay<Parent>::type,
+    return async_traversal_point<Frame, std::decay_t<Parent>, Hierarchy...>(
-                                 Hierarchy...>(frame_, std::move(hierarchy),
+        frame_, std::move(hierarchy), detached_);
-                                               detached_);
   }
 
   /// Forks the current traversal point and continues the child
@@ -405,7 +402,7 @@ public:
   /// Async traverse the current iterator
   template <typename Current>
   void async_traverse_one(Current&& current) {
-    using ElementType = typename std::decay<decltype(*current)>::type;
+    using ElementType = std::decay_t<decltype(*current)>;
     return async_traverse_one_impl(container_category_of_t<ElementType>{},
                                    std::forward<Current>(current));
   }
@@ -422,8 +419,8 @@ public:
   template <std::size_t... Sequence, typename Current>
   void async_traverse_static_async_range(
       std::integer_sequence<std::size_t, Sequence...>, Current&& current) {
-    int dummy[] = {0, ((void)async_traverse_one_checked(
+    int dummy[] = {0, (async_traverse_one_checked(current.relocate(
-                           current.template relocate<Sequence>()),
+                           std::integral_constant<std::size_t, Sequence>{})),
                        0)...};
     (void)dummy;
     (void)current;
@@ -453,8 +450,7 @@ public:
 /// given frame and hierarchy
 template <typename Frame, typename... Hierarchy>
 using traversal_point_of_t =
-    async_traversal_point<typename std::decay<Frame>::type,
+    async_traversal_point<std::decay_t<Frame>, std::decay_t<Hierarchy>...>;
-                          typename std::decay<Hierarchy>::type...>;
 
 /// A callable object which is capable of resuming an asynchronous
 /// pack traversal.
@@ -520,7 +516,7 @@ struct resume_state_callable {
 template <typename Frame, typename State>
 void resume_traversal_callable<Frame, State>::operator()() {
   auto hierarchy = std::tuple_cat(std::make_tuple(frame_), state_);
-  traits::unpack(std::move(hierarchy), resume_state_callable{});
+  traits::unpack(resume_state_callable{}, std::move(hierarchy));
 }
 
 /// Gives access to types related to the traversal frame
@@ -528,8 +524,8 @@ template <typename Visitor, typename... Args>
 struct async_traversal_types {
   /// Deduces to the async traversal frame type of the given
   /// traversal arguments and mapper
-  using frame_t = async_traversal_frame<typename std::decay<Visitor>::type,
+  using frame_t =
-                                        typename std::decay<Args>::type...>;
+      async_traversal_frame<std::decay_t<Visitor>, std::decay_t<Args>...>;
 
   /// The type of the demoted visitor type
   using visitor_t = Visitor;

include/continuable/detail/traversal/traverse.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -37,9 +37,8 @@
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
+#include <continuable/detail/traversal/container-category.hpp>
-#include <continuable/detail/container-category.hpp>
+#include <continuable/detail/utility/traits.hpp>
-#include <continuable/detail/traits.hpp>
 
 namespace cti {
 namespace detail {
@@ -170,8 +169,7 @@ struct flat_arraylizer {
   /// Deduces to the array type when the array is instantiated
   /// with the given arguments.
   template <typename First, typename... Rest>
-  using array_type_of_t =
+  using array_type_of_t = Type<std::decay_t<First>, 1 + sizeof...(Rest)>;
-      Type<typename std::decay<First>::type, 1 + sizeof...(Rest)>;
 
   // We overload with one argument here so Clang and GCC don't
   // have any issues with overloading against zero arguments.
@@ -192,10 +190,10 @@ struct flat_arraylizer {
 template <typename C, typename... T>
 constexpr auto apply_spread_impl(std::true_type, C&& callable, T&&... args)
     -> decltype(
-        traits::unpack(std::tuple_cat(undecorate(std::forward<T>(args))...),
+        traits::unpack(std::forward<C>(callable),
-                       std::forward<C>(callable))) {
+                       std::tuple_cat(undecorate(std::forward<T>(args))...))) {
-  return traits::unpack(std::tuple_cat(undecorate(std::forward<T>(args))...),
+  return traits::unpack(std::forward<C>(callable),
-                        std::forward<C>(callable));
+                        std::tuple_cat(undecorate(std::forward<T>(args))...));
 }
 
 /// Use the linear instantiation for variadic packs which don't
@@ -408,9 +406,8 @@ using element_of_t = typename std::conditional<
 /// Removes all qualifier and references from the given type
 /// if the type is a l-value or r-value reference.
 template <typename T>
-using dereferenced_of_t =
+using dereferenced_of_t = typename std::conditional<std::is_reference<T>::value,
-    typename std::conditional<std::is_reference<T>::value,
+                                                    std::decay_t<T>, T>::type;
-                              typename std::decay<T>::type, T>::type;
 
 /// Returns the type which is resulting if the mapping is applied to
 /// an element in the container.
@@ -424,8 +421,8 @@ using mapped_type_from_t = dereferenced_of_t<spreading::unpacked_of_t<decltype(
 
 /// Deduces to a true_type if the mapping maps to zero elements.
 template <typename T, typename M>
-using is_empty_mapped = spreading::is_empty_spread<typename std::decay<decltype(
+using is_empty_mapped = spreading::is_empty_spread<
-    std::declval<M>()(std::declval<element_of_t<T>>()))>::type>;
+    std::decay_t<decltype(std::declval<M>()(std::declval<element_of_t<T>>()))>>;
 
 /// We are allowed to reuse the container if we map to the same
 /// type we are accepting and when we have
@@ -473,10 +470,9 @@ template <typename M, typename T>
 auto remap_container(container_mapping_tag<false, false>, M&& mapper,
                      T&& container)
     -> decltype(rebind_container<mapped_type_from_t<T, M>>(container)) {
-  static_assert(
+  static_assert(has_push_back<std::decay_t<T>, element_of_t<T>>::value,
-      has_push_back<typename std::decay<T>::type, element_of_t<T>>::value,
+                "Can only remap containers that provide a push_back "
-      "Can only remap containers that provide a push_back "
+                "method!");
-      "method!");
 
   // Create the new container, which is capable of holding
   // the remappped types.
@@ -504,7 +500,7 @@ auto remap_container(container_mapping_tag<false, false>, M&& mapper,
 /// type we accepted such as int -> int.
 template <typename M, typename T>
 auto remap_container(container_mapping_tag<false, true>, M&& mapper,
-                     T&& container) -> typename std::decay<T>::type {
+                     T&& container) -> std::decay_t<T> {
   for (auto&& val : container_accessor_of(std::forward<T>(container))) {
     val = spreading::unpack(
         std::forward<M>(mapper)(std::forward<decltype(val)>(val)));
@@ -630,14 +626,13 @@ struct tuple_like_remapper<
 /// different types.
 template <typename Strategy, typename T, typename M>
 auto remap(Strategy, T&& container, M&& mapper) -> decltype(traits::unpack(
-    std::forward<T>(container),
+    std::declval<
-    std::declval<tuple_like_remapper<Strategy, typename std::decay<M>::type,
+        tuple_like_remapper<Strategy, std::decay_t<M>, std::decay_t<T>>>(),
-                                     typename std::decay<T>::type>>())) {
+    std::forward<T>(container))) {
   return traits::unpack(
-      std::forward<T>(container),
+      tuple_like_remapper<Strategy, std::decay_t<M>, std::decay_t<T>>{
-      tuple_like_remapper<Strategy, typename std::decay<M>::type,
+          std::forward<M>(mapper)},
-                          typename std::decay<T>::type>{
+      std::forward<T>(container));
-          std::forward<M>(mapper)});
 }
 } // end namespace tuple_like_remapping
 
@@ -646,7 +641,7 @@ auto remap(Strategy, T&& container, M&& mapper) -> decltype(traits::unpack(
 template <typename Strategy>
 struct mapping_strategy_base {
   template <typename T>
-  auto may_void(T&& element) const -> typename std::decay<T>::type {
+  auto may_void(T&& element) const -> std::decay_t<T> {
     return std::forward<T>(element);
   }
 };
@@ -804,19 +799,19 @@ class mapping_helper : protected mapping_strategy_base<Strategy> {
   template <typename T>
   auto traverse(Strategy, T&& element)
       -> decltype(std::declval<mapping_helper>().match(
-          std::declval<container_category_of_t<typename std::decay<T>::type>>(),
+          std::declval<container_category_of_t<std::decay_t<T>>>(),
           std::declval<T>()));
 
   /// \copybrief traverse
   template <typename T>
   auto try_traverse(Strategy, T&& element)
       -> decltype(std::declval<mapping_helper>().try_match(
-          std::declval<container_category_of_t<typename std::decay<T>::type>>(),
+          std::declval<container_category_of_t<std::decay_t<T>>>(),
           std::declval<T>())) {
     // We use tag dispatching here, to categorize the type T whether
     // it satisfies the container or tuple like requirements.
     // Then we can choose the underlying implementation accordingly.
-    return try_match(container_category_of_t<typename std::decay<T>::type>{},
+    return try_match(container_category_of_t<std::decay_t<T>>{},
                      std::forward<T>(element));
   }
 
@@ -862,7 +857,7 @@ public:
 /// Traverses the given pack with the given mapper and strategy
 template <typename Strategy, typename Mapper, typename... T>
 decltype(auto) transform(Strategy strategy, Mapper&& mapper, T&&... pack) {
-  mapping_helper<Strategy, typename std::decay<Mapper>::type> helper(
+  mapping_helper<Strategy, std::decay_t<Mapper>> helper(
       std::forward<Mapper>(mapper));
   return helper.init_traverse(strategy, std::forward<T>(pack)...);
 }

include/continuable/detail/utility/identity.hpp

@@ -0,0 +1,54 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_IDENTITY_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_IDENTITY_HPP_INCLUDED
+
+#include <type_traits>
+#include <continuable/detail/features.hpp>
+
+namespace cti {
+namespace detail {
+/// A tagging type for wrapping other types
+template <typename... T>
+struct identity {};
+
+template <typename>
+struct is_identity : std::false_type {};
+template <typename... Args>
+struct is_identity<identity<Args...>> : std::true_type {};
+
+template <typename T>
+using identify = std::conditional_t<is_identity<std::decay_t<T>>::value, T,
+                                    identity<std::decay_t<T>>>;
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_IDENTITY_HPP_INCLUDED

include/continuable/detail/utility/result-trait.hpp

@@ -0,0 +1,101 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_RESULT_TRAIT_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_RESULT_TRAIT_HPP_INCLUDED
+
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <continuable/detail/core/annotation.hpp>
+#include <continuable/detail/utility/traits.hpp>
+#include <continuable/detail/utility/util.hpp>
+
+namespace cti {
+namespace detail {
+struct void_arg_t { };
+
+template <typename... T>
+struct result_trait;
+template <>
+struct result_trait<> {
+  using value_t = void;
+  using surrogate_t = void_arg_t;
+
+  static constexpr surrogate_t wrap() noexcept {
+    return {};
+  }
+
+  static constexpr void unwrap(surrogate_t) {
+  }
+};
+template <typename T>
+struct result_trait<T> {
+  using value_t = T;
+  using surrogate_t = value_t;
+
+  static surrogate_t wrap(T arg) {
+    return std::move(arg);
+  }
+
+  template <typename R>
+  static decltype(auto) unwrap(R&& unwrap) {
+    return std::forward<R>(unwrap);
+  }
+
+  template <std::size_t I, typename Result>
+  static decltype(auto) get(Result&& result) {
+    return std::forward<Result>(result).get_value();
+  }
+};
+template <typename First, typename Second, typename... Rest>
+struct result_trait<First, Second, Rest...> {
+  using value_t = std::tuple<First, Second, Rest...>;
+  using surrogate_t = value_t;
+
+  static surrogate_t wrap(First first, Second second, Rest... rest) {
+    return std::make_tuple(std::move(first), std::move(second),
+                           std::move(rest)...);
+  }
+
+  template <typename R>
+  static decltype(auto) unwrap(R&& unwrap) {
+    return std::forward<R>(unwrap);
+  }
+
+  template <std::size_t I, typename Result>
+  static decltype(auto) get(Result&& result) {
+    return std::get<I>(std::forward<Result>(result).get_value());
+  }
+};
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_RESULT_TRAIT_HPP_INCLUDED

include/continuable/detail/utility/result-variant.hpp

@@ -0,0 +1,217 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_RESULT_VARIANT_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_RESULT_VARIANT_HPP_INCLUDED
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <initializer_list>
+#include <memory>
+#include <type_traits>
+#include <utility>
+#include <continuable/detail/utility/traits.hpp>
+
+namespace cti {
+namespace detail {
+namespace container {
+enum class result_slot_t : std::uint8_t {
+  slot_empty,
+  slot_value,
+  slot_exception,
+};
+} // namespace container
+
+struct init_empty_arg_t {};
+struct init_result_arg_t {};
+struct init_exception_arg_t {};
+
+template <typename T>
+class result_variant {
+  static constexpr bool is_nothrow_destructible = //
+      std::is_nothrow_destructible<T>::value &&
+      std::is_nothrow_destructible<exception_t>::value;
+  static constexpr bool is_nothrow_move_constructible = //
+      std::is_nothrow_move_constructible<T>::value &&
+      std::is_nothrow_move_constructible<exception_t>::value;
+
+public:
+  result_variant() = default;
+  ~result_variant() noexcept(is_nothrow_destructible) {
+    destroy();
+  }
+
+  explicit result_variant(init_empty_arg_t) noexcept
+    : slot_(container::result_slot_t::slot_empty) {}
+  explicit result_variant(init_result_arg_t, T value) noexcept(
+      std::is_nothrow_destructible<T>::value&&
+          std::is_nothrow_move_constructible<T>::value)
+    : slot_(container::result_slot_t::slot_value) {
+    new (value_ptr()) T(std::move(value));
+  }
+  explicit result_variant(init_exception_arg_t, exception_t exception) noexcept(
+      std::is_nothrow_destructible<exception_t>::value&&
+          std::is_nothrow_move_constructible<exception_t>::value)
+    : slot_(container::result_slot_t::slot_exception) {
+    new (exception_ptr()) exception_t(std::move(exception));
+  }
+
+  result_variant(result_variant const&) = delete;
+  result_variant& operator=(result_variant const&) = delete;
+
+  result_variant(result_variant&& other) noexcept(
+      is_nothrow_destructible&& is_nothrow_move_constructible)
+    : slot_(other.slot_) {
+
+    switch (other.slot_) {
+      case container::result_slot_t::slot_value: {
+        new (value_ptr()) T(std::move(*other.value_ptr()));
+        break;
+      }
+      case container::result_slot_t::slot_exception: {
+        new (exception_ptr()) exception_t(std::move(*other.exception_ptr()));
+        break;
+      }
+      default: {
+        break;
+      }
+    }
+
+    other.destroy();
+    other.slot_ = container::result_slot_t::slot_empty;
+  }
+
+  result_variant& operator=(result_variant&& other) noexcept(
+      is_nothrow_destructible&& is_nothrow_move_constructible) {
+
+    destroy();
+    slot_ = other.slot_;
+
+    switch (other.slot_) {
+      case container::result_slot_t::slot_value: {
+        new (value_ptr()) T(std::move(*other.value_ptr()));
+        break;
+      }
+      case container::result_slot_t::slot_exception: {
+        new (exception_ptr()) exception_t(std::move(*other.exception_ptr()));
+        break;
+      }
+      default: {
+        break;
+      }
+    }
+
+    other.destroy();
+    other.slot_ = container::result_slot_t::slot_empty;
+    return *this;
+  }
+
+  void set_empty() {
+    destroy();
+    slot_ = container::result_slot_t::slot_empty;
+  }
+  void set_value(T value) {
+    destroy();
+    new (value_ptr()) T(std::move(value));
+    slot_ = container::result_slot_t::slot_value;
+  }
+  void set_exception(exception_t exception) {
+    destroy();
+    new (exception_ptr()) exception_t(std::move(exception));
+    slot_ = container::result_slot_t::slot_exception;
+  }
+
+  container::result_slot_t slot() const noexcept {
+    return slot_;
+  }
+
+  bool is_empty() const noexcept {
+    return slot_ == container::result_slot_t::slot_empty;
+  }
+  bool is_value() const noexcept {
+    return slot_ == container::result_slot_t::slot_value;
+  }
+  bool is_exception() const noexcept {
+    return slot_ == container::result_slot_t::slot_exception;
+  }
+
+  T& get_value() noexcept {
+    assert(is_value());
+    return *reinterpret_cast<T*>(&storage_);
+  }
+  T const& get_value() const noexcept {
+    assert(is_value());
+    return *reinterpret_cast<T const*>(&storage_);
+  }
+
+  exception_t& get_exception() noexcept {
+    assert(is_exception());
+    return *reinterpret_cast<exception_t*>(&storage_);
+  }
+  exception_t const& get_exception() const noexcept {
+    assert(is_exception());
+    return *reinterpret_cast<exception_t const*>(&storage_);
+  }
+
+private:
+  constexpr T* value_ptr() noexcept {
+    return reinterpret_cast<T*>(&storage_);
+  }
+  constexpr exception_t* exception_ptr() noexcept {
+    return reinterpret_cast<exception_t*>(&storage_);
+  }
+
+  void destroy() noexcept(is_nothrow_destructible) {
+    switch (slot_) {
+      case container::result_slot_t::slot_value: {
+        value_ptr()->~T();
+        break;
+      }
+      case container::result_slot_t::slot_exception: {
+        exception_ptr()->~exception_t();
+        break;
+      }
+      default: {
+        break;
+      }
+    }
+  }
+
+  container::result_slot_t slot_{container::result_slot_t::slot_empty};
+  std::aligned_storage_t<
+      (sizeof(T) > sizeof(exception_t) ? sizeof(T) : sizeof(exception_t)),
+      (alignof(T) > alignof(exception_t) ? alignof(T) : alignof(exception_t))>
+      storage_;
+};
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_RESULT_VARIANT_HPP_INCLUDED

include/continuable/detail/utility/traits.hpp

@@ -0,0 +1,192 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_DETAIL_TRAITS_HPP_INCLUDED
+#define CONTINUABLE_DETAIL_TRAITS_HPP_INCLUDED
+
+#include <cstddef>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <continuable/detail/features.hpp>
+#include <continuable/detail/utility/identity.hpp>
+
+namespace cti {
+namespace detail {
+namespace traits {
+/// Removes all references and qualifiers from the given type T,
+/// since std::decay has too much overhead through checking for
+/// function pointers and arrays also.
+template <typename T>
+using unrefcv_t = std::remove_cv_t<std::remove_reference_t<T>>;
+
+namespace detail {
+template <typename T, typename... Args>
+struct index_of_impl;
+template <typename T, typename... Args>
+struct index_of_impl<T, T, Args...> : std::integral_constant<std::size_t, 0U> {
+};
+template <typename T, typename U, typename... Args>
+struct index_of_impl<T, U, Args...>
+    : std::integral_constant<std::size_t,
+                             1 + index_of_impl<T, Args...>::value> {};
+} // namespace detail
+
+/// Evaluates to the index of T in the given pack
+template <typename T, typename... Args>
+using index_of_t = detail::index_of_impl<T, Args...>;
+
+/// Creates a tuple in which r-values gets copied and
+/// l-values keep their l-value.
+template <typename... T>
+auto make_flat_tuple(T&&... args) {
+  return std::tuple<T...>{std::forward<T>(args)...};
+}
+
+#if defined(CONTINUABLE_HAS_CXX17_VOID_T)
+using std::void_t;
+#else
+namespace detail {
+// Equivalent to C++17's std::void_t which targets a bug in GCC,
+// that prevents correct SFINAE behavior.
+// See http://stackoverflow.com/questions/35753920 for details.
+template <typename...>
+struct deduce_to_void : std::common_type<void> {};
+} // namespace detail
+
+/// C++17 like void_t type
+template <typename... T>
+using void_t = typename detail::deduce_to_void<T...>::type;
+#endif // CONTINUABLE_HAS_CXX17_VOID_T
+
+namespace detail_unpack {
+using std::get;
+
+/// Calls the given unpacker with the content of the given sequenceable
+template <typename U, typename F, std::size_t... I>
+constexpr auto unpack_impl(U&& unpacker, F&& first_sequenceable,
+                           std::integer_sequence<std::size_t, I...>)
+    -> decltype(std::forward<U>(unpacker)(
+        get<I>(std::forward<F>(first_sequenceable))...)) {
+  (void)first_sequenceable;
+  return std::forward<U>(unpacker)(
+      get<I>(std::forward<F>(first_sequenceable))...);
+}
+} // namespace detail_unpack
+
+/// Calls the given callable object with the content of the given sequenceable
+///
+/// \note We can't use std::apply here since this implementation is SFINAE
+///       aware and the std version not! This would lead to compilation errors.
+template <typename Callable, typename TupleLike,
+          typename Sequence = std::make_index_sequence<
+              std::tuple_size<std::decay_t<TupleLike>>::value>>
+constexpr auto unpack(Callable&& obj, TupleLike&& tuple_like)
+    -> decltype(detail_unpack::unpack_impl(std::forward<Callable>(obj),
+                                           std::forward<TupleLike>(tuple_like),
+                                           Sequence{})) {
+
+  return detail_unpack::unpack_impl(std::forward<Callable>(obj),
+                                    std::forward<TupleLike>(tuple_like),
+                                    Sequence{});
+}
+
+namespace detail {
+template <typename T, typename Args, typename = traits::void_t<>>
+struct is_invokable_impl : std::common_type<std::false_type> {};
+
+template <typename T, typename... Args>
+struct is_invokable_impl<
+    T, std::tuple<Args...>,
+    void_t<decltype(std::declval<T>()(std::declval<Args>()...))>>
+    : std::common_type<std::true_type> {};
+} // namespace detail
+
+/// Deduces to a std::true_type if the given type is callable with the arguments
+/// inside the given tuple.
+/// The main reason for implementing it with the detection idiom instead of
+/// hana like detection is that MSVC has issues with capturing raw template
+/// arguments inside lambda closures.
+///
+/// ```cpp
+/// traits::is_invocable<object, std::tuple<Args...>>
+/// ```
+template <typename T, typename Args>
+using is_invocable_from_tuple =
+    typename detail::is_invokable_impl<T, Args>::type;
+
+// Checks whether the given callable object is invocable with the given
+// arguments. This doesn't take member functions into account!
+template <typename T, typename... Args>
+using is_invocable = is_invocable_from_tuple<T, std::tuple<Args...>>;
+
+/// Deduces to a std::false_type
+template <typename T>
+using fail = std::integral_constant<bool, !std::is_same<T, T>::value>;
+
+#ifdef CONTINUABLE_HAS_CXX17_DISJUNCTION
+using std::disjunction;
+#else
+namespace detail {
+/// Declares a C++14 polyfill for C++17 std::disjunction.
+template <typename Args, typename = void_t<>>
+struct disjunction_impl : std::common_type<std::true_type> {};
+template <typename... Args>
+struct disjunction_impl<identity<Args...>,
+                        void_t<std::enable_if_t<!bool(Args::value)>...>>
+    : std::common_type<std::false_type> {};
+} // namespace detail
+
+template <typename... Args>
+using disjunction = typename detail::disjunction_impl<identity<Args...>>::type;
+#endif // CONTINUABLE_HAS_CXX17_DISJUNCTION
+
+#ifdef CONTINUABLE_HAS_CXX17_CONJUNCTION
+using std::conjunction;
+#else
+namespace detail {
+/// Declares a C++14 polyfill for C++17 std::conjunction.
+template <typename Args, typename = void_t<>>
+struct conjunction_impl : std::common_type<std::false_type> {};
+template <typename... Args>
+struct conjunction_impl<identity<Args...>,
+                        void_t<std::enable_if_t<bool(Args::value)>...>>
+    : std::common_type<std::true_type> {};
+} // namespace detail
+
+template <typename... Args>
+using conjunction = typename detail::conjunction_impl<identity<Args...>>::type;
+#endif // CONTINUABLE_HAS_CXX17_CONJUNCTION
+
+} // namespace traits
+} // namespace detail
+} // namespace cti
+
+#endif // CONTINUABLE_DETAIL_TRAITS_HPP_INCLUDED

include/continuable/detail/utility/util.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,7 +21,7 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
@@ -32,108 +32,184 @@
 #define CONTINUABLE_DETAIL_UTIL_HPP_INCLUDED
 
 #include <cassert>
+#include <cstdlib>
 #include <tuple>
 #include <type_traits>
 #include <utility>
-
 #include <continuable/detail/features.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/utility/traits.hpp>
+
+/// Hint for the compiler that this point should be unreachable
+#if defined(_MSC_VER)
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_UNREACHABLE_INTRINSIC() __assume(false)
+#elif defined(__GNUC__)
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_UNREACHABLE_INTRINSIC() __builtin_unreachable()
+#elif defined(__has_builtin) && __has_builtin(__builtin_unreachable)
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_UNREACHABLE_INTRINSIC() __builtin_unreachable()
+#else
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_UNREACHABLE_INTRINSIC() abort()
+#endif
+
+/// Causes the application to exit abnormally
+#if defined(_MSC_VER)
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_TRAP() __debugbreak()
+#elif defined(__GNUC__)
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_TRAP() __builtin_trap()
+#elif defined(__has_builtin) && __has_builtin(__builtin_trap)
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_TRAP() __builtin_trap()
+#else
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_TRAP() *(volatile int*)0x11 = 0
+#endif
+
+#ifndef NDEBUG
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_UNREACHABLE() ::cti::detail::util::unreachable_debug()
+#else
+// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
+#define CTI_DETAIL_UNREACHABLE() CTI_DETAIL_UNREACHABLE_INTRINSIC()
+#endif
 
 namespace cti {
 namespace detail {
 /// Utility namespace which provides useful meta-programming support
 namespace util {
+#ifndef NDEBUG
+  [[noreturn]] inline void unreachable_debug() {
+    CTI_DETAIL_TRAP();
+    std::abort();
+  }
+#endif
+
 /// Helper to trick compilers about that a parameter pack is used
 template <typename... T>
 constexpr void unused(T&&...) noexcept {
 }
 
 namespace detail {
+template <typename T, std::size_t... I>
+auto forward_except_last_impl(T&& tuple,
+                              std::integer_sequence<std::size_t, I...>) {
+  (void)tuple;
+  return std::forward_as_tuple(std::get<I>(std::forward<T>(tuple))...);
+}
+
+template <std::size_t Size>
+constexpr auto make_decreased_index_sequence(
+    std::integral_constant<std::size_t, Size>) noexcept {
+  return std::make_index_sequence<Size - 1>();
+}
+inline void make_decreased_index_sequence(
+    std::integral_constant<std::size_t, 0U>) noexcept {
+  // This function is only instantiated on a compiler error and
+  // should not be included in valid code.
+  // See https://github.com/Naios/continuable/issues/21 for details.
+  CTI_DETAIL_UNREACHABLE();
+}
+
 /// Forwards every element in the tuple except the last one
 template <typename T>
 auto forward_except_last(T&& sequenceable) {
-  constexpr auto const size = pack_size_of(traits::identify<T>()) - 1U;
-  constexpr auto const sequence = std::make_index_sequence<size>();
-
-  return traits::unpack(std::forward<T>(sequenceable),
-                        [](auto&&... args) {
-                          return std::forward_as_tuple(
-                              std::forward<decltype(args)>(args)...);
-                        },
-                        sequence);
-}
-
-/// We are able to call the callable with the arguments given in the tuple
-template <typename T, typename... Args>
-auto partial_invoke_impl(std::true_type, T&& callable,
-                         std::tuple<Args...> args) {
-  return traits::unpack(std::move(args), [&](auto&&... arg) {
-    return std::forward<T>(callable)(std::forward<decltype(arg)>(arg)...);
-  });
-}
-
-/// We were unable to call the callable with the arguments in the tuple.
-/// Remove the last argument from the tuple and try it again.
-template <typename T, typename... Args>
-auto partial_invoke_impl(std::false_type, T&& callable,
-                         std::tuple<Args...> args) {
-
-  // If you are encountering this assertion you tried to attach a callback
-  // which can't accept the arguments of the continuation.
-  //
-  // ```cpp
-  // continuable<int, int> c;
-  // std::move(c).then([](std::vector<int> v) { /*...*/ })
-  // ```
   static_assert(
-      sizeof...(Args) > 0,
+      std::tuple_size<std::decay_t<T>>::value > 0U,
-      "There is no way to call the given object with these arguments!");
+      "Attempt to remove a parameter from an empty tuple like type! If you see "
+      "this your compiler could run into possible infinite recursion! Open a "
+      "ticket at https://github.com/Naios/continuable/issues with a small "
+      "reproducible example if your compiler doesn't stop!");
 
-  // Remove the last argument from the tuple
+  constexpr auto size = std::tuple_size<std::decay_t<T>>::value;
-  auto next = forward_except_last(std::move(args));
+  constexpr auto sequence = make_decreased_index_sequence(
+      std::integral_constant<std::size_t, size>{});
 
-  // Test whether we are able to call the function with the given tuple
+  return forward_except_last_impl(std::forward<T>(sequenceable), sequence);
-  traits::is_invokable_from_tuple<decltype(callable), decltype(next)>
-      is_invokable;
-
-  return partial_invoke_impl(is_invokable, std::forward<T>(callable),
-                             std::move(next));
 }
 
-/// Shortcut - we can call the callable directly
+template <std::size_t Keep>
-template <typename T, typename... Args>
+struct invocation_env {
-auto partial_invoke_impl_shortcut(std::true_type, T&& callable,
+  /// We are able to call the callable with the arguments given in the tuple
-                                  Args&&... args) {
+  template <typename T, typename... Args>
-  return std::forward<T>(callable)(std::forward<Args>(args)...);
+  static auto partial_invoke_impl(std::true_type, T&& callable,
-}
+                                  std::tuple<Args...> args) {
+    return traits::unpack(std::forward<T>(callable), std::move(args));
+  }
 
-/// Failed shortcut - we were unable to invoke the callable with the
+  /// We were unable to call the callable with the arguments in the tuple.
-/// original arguments.
+  /// Remove the last argument from the tuple and try it again.
-template <typename T, typename... Args>
+  template <typename T, typename... Args>
-auto partial_invoke_impl_shortcut(std::false_type failed, T&& callable,
+  static auto partial_invoke_impl(std::false_type, T&& callable,
-                                  Args&&... args) {
+                                  std::tuple<Args...> args) {
 
-  // Our shortcut failed, convert the arguments into a forwarding tuple
+    // If you are encountering this assertion you tried to attach a callback
-  return partial_invoke_impl(
+    // which can't accept the arguments of the continuation.
-      failed, std::forward<T>(callable),
+    //
-      std::forward_as_tuple(std::forward<Args>(args)...));
+    // ```cpp
-}
+    // continuable<int, int> c;
+    // std::move(c).then([](std::vector<int> v) { /*...*/ })
+    // ```
+    static_assert(
+        sizeof...(Args) > Keep,
+        "There is no way to call the given object with these arguments!");
+
+    // Remove the last argument from the tuple
+    auto next = forward_except_last(std::move(args));
+
+    // Test whether we are able to call the function with the given tuple
+    constexpr std::integral_constant<
+        bool, traits::is_invocable_from_tuple<decltype(callable),
+                                              decltype(next)>::value ||
+                  (sizeof...(Args) <= Keep)>
+        is_callable;
+
+    return partial_invoke_impl(is_callable, std::forward<T>(callable),
+                               std::move(next));
+  }
+
+  /// Shortcut - we can call the callable directly
+  template <typename T, typename... Args>
+  static auto partial_invoke_impl_shortcut(std::true_type, T&& callable,
+                                           Args&&... args) {
+    return std::forward<T>(callable)(std::forward<Args>(args)...);
+  }
+
+  /// Failed shortcut - we were unable to invoke the callable with the
+  /// original arguments.
+  template <typename T, typename... Args>
+  static auto partial_invoke_impl_shortcut(std::false_type failed, T&& callable,
+                                           Args&&... args) {
+
+    // Our shortcut failed, convert the arguments into a forwarding tuple
+    return partial_invoke_impl(
+        failed, std::forward<T>(callable),
+        std::forward_as_tuple(std::forward<Args>(args)...));
+  }
+};
 } // namespace detail
 
 /// Partially invokes the given callable with the given arguments.
 ///
 /// \note This function will assert statically if there is no way to call the
 ///       given object with less arguments.
-template <typename T, typename... Args>
+template <std::size_t KeepArgs, typename T, typename... Args>
-/*keep this inline*/ inline auto partial_invoke(T&& callable, Args&&... args) {
+/*keep this inline*/ inline auto
+partial_invoke(std::integral_constant<std::size_t, KeepArgs>, T&& callable,
+               Args&&... args) {
   // Test whether we are able to call the function with the given arguments.
-  traits::is_invokable_from_tuple<decltype(callable), std::tuple<Args...>>
+  constexpr traits::is_invocable_from_tuple<decltype(callable),
-      is_invokable;
+                                            std::tuple<Args...>>
+      is_invocable;
 
   // The implementation is done in a shortcut way so there are less
   // type instantiations needed to call the callable with its full signature.
-  return detail::partial_invoke_impl_shortcut(
+  using env = detail::invocation_env<KeepArgs>;
-      is_invokable, std::forward<T>(callable), std::forward<Args>(args)...);
+  return env::partial_invoke_impl_shortcut(
+      is_invocable, std::forward<T>(callable), std::forward<Args>(args)...);
 }
 
 /// Invokes the given callable object with the given arguments
@@ -161,6 +237,12 @@ constexpr auto invoke(Type T::*member, Self&& self, Args&&... args) noexcept(
   return (std::forward<Self>(self)->*member)(std::forward<Args>(args)...);
 }
 
+/// Returns a constant view on the object
+template <typename T>
+constexpr std::add_const_t<T>& as_const(T& object) noexcept {
+  return object;
+}
+
 // Class for making child classes non copyable
 struct non_copyable {
   constexpr non_copyable() = default;
@@ -237,39 +319,8 @@ private:
   /// Is true when the automatic invocation on destruction is disabled
   bool frozen_ : 1;
 };
-
-/// Hint for the compiler that this point should be unreachable
-[[noreturn]] inline void unreachable() {
-#if defined(_MSC_VER)
-  __assume(false);
-#elif defined(__GNUC__)
-  __builtin_unreachable();
-#elif defined(__has_builtin) && __has_builtin(__builtin_unreachable)
-  __builtin_unreachable();
-#endif
-}
-
-/// Causes the application to exit abnormally because we are
-/// in an invalid state.
-[[noreturn]] inline void trap() {
-#if defined(_MSC_VER)
-  __debugbreak();
-#elif defined(__GNUC__)
-  __builtin_trap();
-#elif defined(__has_builtin) && __has_builtin(__builtin_trap)
-  __builtin_trap();
-#else
-  *(volatile int*)0 = 0;
-#endif
-}
 } // namespace util
 } // namespace detail
 } // namespace cti
 
-#ifdef CONTINUABLE_CONSTEXPR_IF
-#define CONTINUABLE_CONSTEXPR_IF(EXPR, TRUE_BRANCH, FALSE_BRANCH)
-#else
-#define CONTINUABLE_CONSTEXPR_IF(EXPR, TRUE_BRANCH, FALSE_BRANCH)
-#endif // CONTINUABLE_CONSTEXPR_IF
-
 #endif // CONTINUABLE_DETAIL_UTIL_HPP_INCLUDED

include/continuable/external/asio.hpp

@@ -0,0 +1,183 @@
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_EXTERNAL_ASIO_HPP_INCLUDED
+#define CONTINUABLE_EXTERNAL_ASIO_HPP_INCLUDED
+
+#include <continuable/continuable-base.hpp>
+#include <continuable/detail/external/asio.hpp>
+#include <continuable/detail/utility/traits.hpp>
+
+namespace cti {
+/// The error code type used by your asio distribution
+///
+/// \since 4.1.0
+using asio_error_code_t = detail::asio::error_code_t;
+
+/// The basic error code enum used by your asio distribution
+///
+/// \since 4.1.0
+using asio_basic_errors_t = detail::asio::basic_errors_t;
+
+#if defined(CONTINUABLE_HAS_EXCEPTIONS)
+/// The system error type used by your asio distribution
+///
+/// \since 4.1.0
+using asio_system_error_t = detail::asio::system_error_t;
+#endif // CONTINUABLE_HAS_EXCEPTIONS
+
+/// Type used as an ASIO completion token to specify an asynchronous operation
+/// that should return a continuable_base.
+///
+/// - Boost 1.70 or asio 1.13.0 is required for the async initiation
+/// - Until boost 1.72 or asio 1.16.0 overhead through an additional type
+///   erasure is added. It is recommended to update to those versions.
+///
+/// The special static variable use_continuable can be appended to any
+/// (boost) asio function that accepts a callback to make it return a
+/// continuable_base.
+///
+/// ```cpp
+/// #include <continuable/continuable.hpp>
+/// #include <continuable/external/asio.hpp>
+/// #include <asio.hpp>
+///
+/// // ...
+///
+/// asio::tcp::resolver resolver(...);
+/// resolver.async_resolve("127.0.0.1", "daytime", cti::use_continuable)
+///   .then([](asio::udp::resolver::iterator iterator) {
+///     // ...
+///   });
+/// ```
+///
+/// \tparam Mapper The token can be instantiated with a custom mapper
+///         for asio error codes which makes it possible to ignore
+///         errors or treat them as cancellation types.
+///         The mapper has the following form:
+/// ```
+/// struct my_mapper {
+///   constexpr my_mapper() noexcept {}
+///
+///   /// Returns true when the error_code_t is a type which represents
+///   /// cancellation and
+///   bool is_cancellation(error_code_t const& /*ec*/) const noexcept {
+///     return false;
+///   }
+///   bool is_ignored(error_code_t const& /*ec*/) const noexcept {
+///     return false;
+///   }
+/// };
+/// ```
+///
+/// \attention `asio::error::basic_errors::operation_aborted` errors returned
+///            by asio are automatically transformed into a default constructed
+///            exception type which represents "operation canceled" by the
+///            user or program. If you intend to retrieve the full
+///            asio::error_code without remapping use the use_continuable_raw_t
+///            completion token instead!
+///
+/// \since 4.0.0
+template <typename Mapper = detail::asio::map_default>
+struct use_continuable_t : public Mapper {
+  using Mapper::Mapper;
+};
+
+/// \copydoc use_continuable_t
+///
+/// The raw async completion handler token does not remap the asio error
+/// `asio::error::basic_errors::operation_aborted` to a default constructed
+/// exception type.
+///
+/// \since 4.1.0
+using use_continuable_raw_t = use_continuable_t<detail::asio::map_none>;
+
+/// Special value for instance of use_continuable_t which performs remapping
+/// of asio error codes to align the cancellation behaviour with the library.
+///
+/// \copydetails use_continuable_t
+constexpr use_continuable_t<> use_continuable{};
+
+/// Special value for instance of use_continuable_raw_t which doesn't perform
+/// remapping of asio error codes and rethrows the raw error code.
+///
+/// \copydetails use_continuable_raw_t
+constexpr use_continuable_raw_t use_continuable_raw{};
+
+/// Represents a special asio completion token which treats the given
+/// asio basic error codes as success instead of failure.
+///
+/// `asio::error::basic_errors::operation_aborted` is mapped
+/// as cancellation token.
+///
+/// \since 4.1.0
+template <typename... Args>
+auto use_continuable_ignoring(Args&&... args) noexcept {
+  return use_continuable_t<detail::asio::map_ignore<sizeof...(Args)>>{
+      {asio_basic_errors_t(std::forward<Args>(args))...}};
+}
+} // namespace cti
+
+CTI_DETAIL_ASIO_NAMESPACE_BEGIN
+
+template <typename Signature, typename Matcher>
+class async_result<cti::use_continuable_t<Matcher>, Signature> {
+public:
+#if defined(CTI_DETAIL_ASIO_HAS_EXPLICIT_RET_TYPE_INTEGRATION)
+  using return_type = typename cti::detail::asio::initiate_make_continuable<
+      Signature>::erased_return_type;
+#endif
+
+  template <typename Initiation, typename... Args>
+  static auto initiate(Initiation initiation,
+                       cti::use_continuable_t<Matcher> token, Args... args) {
+    return cti::detail::asio::initiate_make_continuable<Signature>{}(
+        [initiation = std::move(initiation), token = std::move(token),
+         init_args = std::make_tuple(std::move(args)...)](
+            auto&& promise) mutable {
+          cti::detail::traits::unpack(
+              [initiation = std::move(initiation),
+               handler = cti::detail::asio::promise_resolver_handler(
+                   std::forward<decltype(promise)>(promise), std::move(token))](
+                  auto&&... args) mutable {
+                std::move(initiation)(std::move(handler),
+                                      std::forward<decltype(args)>(args)...);
+              },
+              std::move(init_args));
+        });
+  }
+};
+
+CTI_DETAIL_ASIO_NAMESPACE_END
+
+#undef CTI_DETAIL_ASIO_NAMESPACE_BEGIN
+#undef CTI_DETAIL_ASIO_NAMESPACE_END
+#undef CTI_DETAIL_ASIO_HAS_EXPLICIT_RET_TYPE_INTEGRATION
+
+#endif // CONTINUABLE_EXTERNAL_ASIO_HPP_INCLUDED

include/continuable/external/gtest.hpp

@@ -5,9 +5,9 @@
                         \_,(_)| | | || ||_|(_||_)|(/_
 
                     https://github.com/Naios/continuable
-                                   v3.0.0
+                                   v4.2.0
 
-  Copyright(c) 2015 - 2018 Denis Blank <denis.blank at outlook dot com>
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
 
   Permission is hereby granted, free of charge, to any person obtaining a copy
   of this software and associated documentation files(the "Software"), to deal
@@ -21,18 +21,18 @@
 
   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   SOFTWARE.
 **/
 
-#ifndef CONTINUABLE_TESTING_HPP_INCLUDED
+#ifndef CONTINUABLE_EXTERNAL_GTEST_HPP_INCLUDED
-#define CONTINUABLE_TESTING_HPP_INCLUDED
+#define CONTINUABLE_EXTERNAL_GTEST_HPP_INCLUDED
 
-#include <continuable/detail/testing.hpp>
+#include <continuable/detail/other/testing.hpp>
-#include <continuable/detail/traits.hpp>
+#include <continuable/detail/utility/traits.hpp>
 
 /// \defgroup Testing Testing
 /// provides macro shortcuts for testing asynchronous continuations through
@@ -53,6 +53,14 @@
 #define ASSERT_ASYNC_EXCEPTION_COMPLETION(CONTINUABLE)                         \
   cti::detail::testing::assert_async_exception_completion(CONTINUABLE);
 
+/// Asserts that the final callback of the given continuable is called
+/// with a cancelled result which is represented by a default constructed
+/// exception_t.
+///
+/// \since 4.0.0
+#define ASSERT_ASYNC_CANCELLATION(CONTINUABLE)                                 \
+  cti::detail::testing::assert_async_cancellation(CONTINUABLE);
+
 /// Asserts that the final callback of the given continuable is never called
 /// with any result.
 ///
@@ -158,7 +166,7 @@
 /// \since 1.0.0
 #define ASSERT_ASYNC_TYPES(CONTINUABLE, ...)                                   \
   cti::detail::testing::assert_async_types(                                    \
-      CONTINUABLE, cti::detail::traits::identity<__VA_ARGS__>{})
+      CONTINUABLE, cti::detail::identity<__VA_ARGS__>{})
 
 /// Asserts that the continuable is finished with the given exception
 ///
@@ -169,4 +177,4 @@
 
 /// \}
 
-#endif // CONTINUABLE_TESTING_HPP_INCLUDED
+#endif // CONTINUABLE_EXTERNAL_GTEST_HPP_INCLUDED

include/continuable/operations/async.hpp

@@ -0,0 +1,116 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_OPERATIONS_ASYNC_HPP_INCLUDED
+#define CONTINUABLE_OPERATIONS_ASYNC_HPP_INCLUDED
+
+#include <utility>
+#include <continuable/detail/core/types.hpp>
+#include <continuable/detail/operations/async.hpp>
+
+namespace cti {
+/// \ingroup Operations
+/// \{
+
+/// Wraps the given callable inside a continuable_base such that it is
+/// invoked when the asynchronous result is requested to return the result.
+///
+/// The async function shall be seen as an equivalent to std::async.
+///
+/// The behaviour will be equal as when using make_ready_continuable together
+/// with continuable_base::then, but async is implemented in
+/// a more efficient way:
+/// ```cpp
+/// auto do_sth() {
+///   return async([] {
+///     do_sth_more();
+///     return 0;
+///   });
+/// }
+/// ```
+///
+/// \param callable The callable type which is invoked on request.
+///
+/// \param args The arguments which are passed to the callable upon invocation.
+///
+/// \returns A continuable_base which asynchronous result type will
+///          be computed with the same rules as continuable_base::then .
+///
+/// \since 4.0.0
+///
+template <typename Callable, typename... Args>
+auto async(Callable&& callable, Args&&... args) {
+  return detail::operations::async(std::forward<Callable>(callable),
+                                   detail::types::this_thread_executor_tag{},
+                                   std::forward<Args>(args)...);
+}
+
+/// Wraps the given callable inside a continuable_base such that it is
+/// invoked through the given executor when the asynchronous result
+/// is requested to return the result.
+///
+/// The behaviour will be equal as when using make_ready_continuable together
+/// with continuable_base::then and the given executor but async_on
+/// is implemented in a more efficient way:
+/// ```cpp
+/// auto do_sth() {
+///   auto executor = [](auto&& work) {
+///     // Do something with the work here
+///     std::forward<decltype(work)>(work);
+///   };
+///
+///   return async_on([] {
+///     do_sth_more();
+///     return 0;
+///   }, my_executor);
+/// }
+/// ```
+///
+/// \param callable The callable type which is invoked on request.
+///
+/// \param executor The executor that is used to dispatch the given callable.
+///
+/// \param args The arguments which are passed to the callable upon invocation.
+///
+/// \returns A continuable_base which asynchronous result type will
+///          be computed with the same rules as continuable_base::then .
+///
+/// \since 4.0.0
+///
+template <typename Callable, typename Executor, typename... Args>
+auto async_on(Callable&& callable, Executor&& executor, Args&&... args) {
+  return detail::operations::async(std::forward<Callable>(callable),
+                                   std::forward<Executor>(executor),
+                                   std::forward<Args>(args)...);
+}
+/// \}
+} // namespace cti
+
+#endif // CONTINUABLE_OPERATIONS_ASYNC_HPP_INCLUDED

include/continuable/operations/loop.hpp

@@ -0,0 +1,141 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_OPERATIONS_LOOP_HPP_INCLUDED
+#define CONTINUABLE_OPERATIONS_LOOP_HPP_INCLUDED
+
+#include <utility>
+#include <continuable/continuable-primitives.hpp>
+#include <continuable/continuable-result.hpp>
+#include <continuable/detail/operations/loop.hpp>
+
+namespace cti {
+/// \ingroup Operations
+/// \{
+
+/// Can be used to create an asynchronous loop.
+///
+/// The callable will be called repeatedly until it returns a
+/// cti::continuable_base which then resolves to a present cti::result.
+///
+/// For better readability cti::loop_result, cti::loop_break and
+/// cti::loop_continue are provided which can be used as following:
+/// ```cpp
+/// auto while_answer_not_yes() {
+///   return loop([] {
+///     return ask_something().then([](std::string answer) -> loop_result<> {
+///       if (answer == "yes") {
+///         return loop_break();
+///       } else {
+///         return loop_continue();
+///       }
+///     });
+///   });
+/// }
+/// ```
+///
+/// \param callable The callable type which must return a cti::continuable_base
+///        which then resolves to a cti::result of arbitrary values.
+///
+/// \param args The arguments that are passed to the callable upon
+///             each invocation.
+///
+/// \since 4.0.0
+///
+template <typename Callable, typename... Args>
+auto loop(Callable&& callable, Args&&... args) {
+  return detail::operations::loop(std::forward<Callable>(callable),
+                                  std::forward<Args>(args)...);
+}
+
+/// Can be used to indicate a specific result inside an asynchronous loop.
+///
+/// See cti::loop for details.
+///
+/// \since 4.0.0
+template <typename... T>
+using loop_result = plain_t<result<T...>>;
+
+/// Can be used to create a loop_result which causes the loop to be
+/// cancelled and resolved with the given arguments.
+///
+/// See cti::loop for details.
+///
+/// \since 4.0.0
+template <typename... T>
+auto loop_break(T&&... args) {
+  return make_plain(make_result(std::forward<T>(args)...));
+}
+
+/// Can be used to create a loop_result which causes the loop to be repeated.
+///
+/// See cti::loop for details.
+///
+/// \since 4.0.0
+inline auto loop_continue() noexcept {
+  return empty_result{};
+}
+
+/// Can be used to create an asynchronous loop over a specific range.
+///
+/// The callable will be called repeatedly with each with begin increased
+/// until end is reached.
+///
+/// ```cpp
+/// auto iterate_some() {
+///   // Iterate step from 0 to 9
+///   return range_loop([] (int step) {
+///     return do_something(i).then([] {
+///       // You don't have to return a result here
+///     });
+///   }, 0, 10);
+/// }
+/// ```
+///
+/// \param callable The callable type which must return a cti::continuable_base
+///        which then resolves to a cti::result of arbitrary values.
+///
+/// \param begin The iterator to iterate over
+///
+/// \param end The iterator to iterate until
+///
+/// \since 4.0.0
+///
+template <typename Callable, typename Iterator>
+auto range_loop(Callable&& callable, Iterator begin, Iterator end) {
+  return detail::operations::loop( //
+      detail::operations::make_range_looper(std::forward<Callable>(callable),
+                                            begin, end));
+}
+
+/// \}
+} // namespace cti
+
+#endif // CONTINUABLE_OPERATIONS_LOOP_HPP_INCLUDED

include/continuable/operations/split.hpp

@@ -0,0 +1,96 @@
+
+/*
+
+                        /~` _  _ _|_. _     _ |_ | _
+                        \_,(_)| | | || ||_|(_||_)|(/_
+
+                    https://github.com/Naios/continuable
+                                   v4.2.0
+
+  Copyright(c) 2015 - 2022 Denis Blank <denis.blank at outlook dot com>
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files(the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions :
+
+  The above copyright notice and this permission notice shall be included in
+  all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+**/
+
+#ifndef CONTINUABLE_OPERATIONS_SPLIT_HPP_INCLUDED
+#define CONTINUABLE_OPERATIONS_SPLIT_HPP_INCLUDED
+
+#include <utility>
+#include <continuable/detail/operations/split.hpp>
+#include <continuable/detail/utility/traits.hpp>
+
+namespace cti {
+/// \ingroup Operations
+/// \{
+
+/// Splits the asynchronous control flow and merges multiple promises/callbacks
+/// together, which take the same types of arguments, into one.
+///
+/// The invocation order of all promises is undefined.
+///
+/// The split function is the opposite of the connection functions
+/// like `when_all` because is can merge multiple waiters together rather than
+/// joining those.
+///
+/// The split function can be used to resolve multiple waiters when resolving
+/// a single promise.
+/// ```cpp
+/// class my_class {
+///   cti::promise<> promise_;
+///
+/// public:
+///   cti::continuable<> wait_for_sth() {
+///     return [this](auto&& promise) mutable {
+///       // Make sure accessing promise_ is done in a thread safe way!
+///       promise_ = cti::split(std::move(promise_),
+///                             std::forward<decltype(promise)>(promise));
+///     };
+///   }
+///
+///   void resolve_all() {
+///     // Resolves all waiting promises
+///     promise_.set_value();
+///   }
+/// };
+/// ```
+///
+/// \note The split function only works if all asynchronous arguments are
+///       copyable. All asynchronous arguments and exceptions will be passed
+///       to all split promises.
+///
+/// \param promises The promises to split the control flow into,
+///                 can be single promises or heterogeneous or homogeneous
+///                 containers of promises (see traverse_pack for a description
+///                 of supported nested arguments).
+///
+/// \returns A new promise with the same asynchronous result types as
+///          the given promises.
+///
+/// \since 4.0.0
+///
+template <typename... Promises>
+auto split(Promises&&... promises) {
+  return detail::operations::split_promise<
+      detail::traits::unrefcv_t<Promises>...>(
+      std::forward<Promises>(promises)...);
+}
+/// \}
+} // namespace cti
+
+#endif // CONTINUABLE_OPERATIONS_SPLIT_HPP_INCLUDED