Fixes array access with arithmetic conversions

Closes #156

include/chaiscript/dispatchkit/proxy_functions.hpp

@@ -717,8 +717,18 @@ namespace chaiscript
               {
                 matching_func = begin;
               } else {
-                // More than one function matches, not attempting
+                // handle const members vs non-const member, which is not really ambiguous
-                throw exception::dispatch_error(plist, std::vector<Const_Proxy_Function>(orig, end));
+                const auto &mat_fun_param_types = (*matching_func)->get_param_types();
+                const auto &next_fun_param_types = (*begin)->get_param_types();
+
+                if (plist[0].is_const() && !mat_fun_param_types[1].is_const() && next_fun_param_types[1].is_const()) {
+                  matching_func = begin; // keep the new one, the const/non-const matchup is correct
+                } else if (!plist[0].is_const() && !mat_fun_param_types[1].is_const() && next_fun_param_types[1].is_const()) {
+                  // keep the old one, it has a better const/non-const matchup
+                } else {
+                  // ambiguous function call
+                  throw exception::dispatch_error(plist, std::vector<Const_Proxy_Function>(orig, end));
+                }
               }
             }
 
@@ -803,12 +813,6 @@ namespace chaiscript
               return (*(func.second))(plist, t_conversions);
             }
           } catch (const exception::bad_boxed_cast &) {
-            //std::cout << "Bad Boxed Cast: " << func.second->get_arity() << '(';
-            //for (const auto &p : plist) {
-            //  std::cout << p.get_type_info().name() << ',';
-            //}
-            //std::cout << ")\n";
-
             //parameter failed to cast, try again
           } catch (const exception::arity_error &) {
             //invalid num params, try again

unittests/vector_access.chai

@@ -2,7 +2,9 @@ auto x = [1, 2, 3]
 assert_equal(3, x[2])
 
 
-for (auto i = x.size() - 1; i >= 0; --i)
+for (auto i = x.size()-1; i > 0; --i)
 {
+  print("Index: " + to_string(i))
   print(x[i]);
+  x[i] = 23;
 }