Merge c7cddbe20b2caf5f9609d2ea357dd88eb8c5ba6b into 3bf72420c2a66531e1ff2f76352542da895b356a

include/chaiscript/dispatchkit/bootstrap_stl.hpp

@@ -219,6 +219,51 @@ namespace chaiscript
         }
 
 
+      /// Add random_access_advance_container concept to the given ContainerType, using advance.
+      /// http://www.sgi.com/tech/stl/RandomAccessContainer.html
+      template<typename ContainerType>
+        void random_access_advance_container_type(const std::string &/*type*/, Module& m)
+        {
+          //In the interest of runtime safety for the m, we prefer the at() method for [] access,
+          //to throw an exception in an out of bounds condition.
+          m.add(
+              fun(
+                [](ContainerType &c, int index) -> typename ContainerType::reference {
+                  /// \todo we are prefering to keep the key as 'int' to avoid runtime conversions
+                  /// during dispatch. reevaluate
+                  auto itr = c.begin();
+                  auto end = c.end();
+                  if (index < 0 || std::distance(itr, end) < index)
+                  {
+                    throw std::range_error("Desired index out of range");
+                  }
+                  std::advance(itr, index);
+                  return *itr;
+                }), "[]");
+
+          m.add(
+              fun(
+                [](const ContainerType &c, int index) -> typename ContainerType::const_reference {
+                  /// \todo we are prefering to keep the key as 'int' to avoid runtime conversions
+                  /// during dispatch. reevaluate
+                  auto itr = c.begin();
+                  auto end = c.end();
+                  if (index < 0 || std::distance(itr, end) < index)
+                  {
+                    throw std::range_error("Desired index out of range");
+                  }
+                  std::advance(itr, index);
+                  return *itr;
+                }), "[]");
+        }
+      template<typename ContainerType>
+        ModulePtr random_access_advance_container_type(const std::string &type)
+        {
+          auto m = std::make_shared<Module>();
+          random_access_advance_container_type<ContainerType>(type, *m);
+          return m;
+        }
+
 
       /// Add assignable concept to the given ContainerType
       /// http://www.sgi.com/tech/stl/Assignable.html
@@ -591,6 +636,7 @@ namespace chaiscript
           default_constructible_type<ListType>(type, m);
           assignable_type<ListType>(type, m);
           input_range_type<ListType>(type, m);
+          random_access_advance_container_type<ListType>(type, m);
         }
       template<typename ListType>
         ModulePtr list_type(const std::string &type)

unittests/list_push_back.chai

@@ -7,6 +7,5 @@ x.push_back("A")
 assert_equal(3, x.front());
 assert_equal("A", x.back());
 
-
+// Random access with List objects.
-
+assert_equal("A", x[1])
-