From 14eaefdceba3be88265a6992b677292ba8dcbf4c Mon Sep 17 00:00:00 2001
From: Jason Turner <jason@emptycrate.com>
Date: Wed, 19 Jul 2017 15:52:34 -0600
Subject: [PATCH] Make `front()` `back()` checked

---
 .../chaiscript/dispatchkit/bootstrap_stl.hpp  | 69 ++++++++++++++++---
 1 file changed, 58 insertions(+), 11 deletions(-)

diff --git a/include/chaiscript/dispatchkit/bootstrap_stl.hpp b/include/chaiscript/dispatchkit/bootstrap_stl.hpp
index 6710ed00..7f409a3a 100644
--- a/include/chaiscript/dispatchkit/bootstrap_stl.hpp
+++ b/include/chaiscript/dispatchkit/bootstrap_stl.hpp
@@ -335,9 +335,24 @@ namespace chaiscript
       template<typename ContainerType>
         void back_insertion_sequence_type(const std::string &type, Module& m)
         {
-          typedef typename ContainerType::reference (ContainerType::*backptr)();
-
-          m.add(fun(static_cast<backptr>(&ContainerType::back)), "back");
+          m.add(fun([](ContainerType &container)->decltype(auto){ 
+                      if (container.empty()) {
+                        throw std::range_error("Container empty");
+                      } else {
+                        return (container.back());
+                      }
+                    }
+                  )
+                , "back");
+          m.add(fun([](const ContainerType &container)->decltype(auto){ 
+                      if (container.empty()) {
+                        throw std::range_error("Container empty");
+                      } else {
+                        return (container.back());
+                      }
+                    }
+                  )
+                , "back");
 
 
           typedef void (ContainerType::*push_back)(const typename ContainerType::value_type &);
@@ -380,13 +395,29 @@ namespace chaiscript
       template<typename ContainerType>
         void front_insertion_sequence_type(const std::string &type, Module& m)
         {
-          typedef typename ContainerType::reference (ContainerType::*front_ptr)();
-          typedef typename ContainerType::const_reference (ContainerType::*const_front_ptr)() const;
           typedef void (ContainerType::*push_ptr)(typename ContainerType::const_reference);
           typedef void (ContainerType::*pop_ptr)();
 
-          m.add(fun(static_cast<front_ptr>(&ContainerType::front)), "front");
-          m.add(fun(static_cast<const_front_ptr>(&ContainerType::front)), "front");
+          m.add(fun([](ContainerType &container)->decltype(auto){ 
+                      if (container.empty()) {
+                        throw std::range_error("Container empty");
+                      } else {
+                        return (container.front());
+                      }
+                    }
+                  )
+                , "front");
+
+          m.add(fun([](const ContainerType &container)->decltype(auto){ 
+                      if (container.empty()) {
+                        throw std::range_error("Container empty");
+                      } else {
+                        return (container.front());
+                      }
+                    }
+                  )
+                , "front");
+
 
           m.add(fun(static_cast<push_ptr>(&ContainerType::push_front)),
               [&]()->std::string{
@@ -577,11 +608,27 @@ namespace chaiscript
         {
           m.add(user_type<VectorType>(), type);
 
-          typedef typename VectorType::reference (VectorType::*frontptr)();
-          typedef typename VectorType::const_reference (VectorType::*constfrontptr)() const;
+          m.add(fun([](VectorType &container)->decltype(auto){ 
+                      if (container.empty()) {
+                        throw std::range_error("Container empty");
+                      } else {
+                        return (container.front());
+                      }
+                    }
+                  )
+                , "front");
+
+          m.add(fun([](const VectorType &container)->decltype(auto){ 
+                      if (container.empty()) {
+                        throw std::range_error("Container empty");
+                      } else {
+                        return (container.front());
+                      }
+                    }
+                  )
+                , "front");
+
 
-          m.add(fun(static_cast<frontptr>(&VectorType::front)), "front");
-          m.add(fun(static_cast<constfrontptr>(&VectorType::front)), "front");
 
 
           back_insertion_sequence_type<VectorType>(type, m);