Remove boost::any requirement by providing our own implementation

include/chaiscript/dispatchkit/any.hpp

@@ -0,0 +1,162 @@
+// This file is distributed under the BSD License.
+// See "license.txt" for details.
+// Copyright 2009-2011, Jonathan Turner (jonathan@emptycrate.com)
+// and Jason Turner (jason@emptycrate.com)
+// http://www.chaiscript.com
+
+#ifndef CHAISCRIPT_ANY_HPP_
+#define CHAISCRIPT_ANY_HPP_
+
+namespace chaiscript {
+  namespace detail {
+    namespace exception
+    {
+      /// \brief Thrown in the event that an Any cannot be cast to the desired type
+      ///
+      /// It is used internally during function dispatch.
+      ///
+      /// \sa chaiscript::detail::Any
+      class bad_any_cast : public std::bad_cast
+      {
+        public:
+          bad_any_cast() throw()
+            : m_what("bad any cast")
+          {
+          }
+
+          virtual ~bad_any_cast() throw() {}
+
+          /// \brief Description of what error occured
+          virtual const char * what() const throw()
+          {
+            return m_what.c_str();
+          }
+
+        private:
+          std::string m_what;
+      };
+    }
+  
+
+    class Any {
+      private:
+        struct Data
+        {
+          virtual void *data() = 0;
+          virtual const std::type_info &type() const = 0;
+          virtual std::shared_ptr<Data> clone() const = 0;
+        };
+
+        template<typename T>
+          struct Data_Impl : Data
+          {
+            Data_Impl(const T &t_type)
+              : m_type(typeid(T)),
+                m_data(t_type)
+            {
+            }
+
+            virtual void *data()
+            {
+              return &m_data;
+            }
+
+            const std::type_info &type() const
+            {
+              return m_type;
+            }
+
+            std::shared_ptr<Data> clone() const
+            {
+              return std::shared_ptr<Data>(new Data_Impl<T>(m_data));
+            }
+
+            const std::type_info &m_type;
+            T m_data;
+          };
+
+        std::shared_ptr<Data> m_data;
+
+      public:
+        // construct/copy/destruct
+        Any() {}
+
+        Any(const Any &t_any) 
+        { 
+          if (!t_any.empty())
+          {
+            m_data = t_any.m_data->clone(); 
+          } else {
+            m_data.reset();
+          }
+        }
+
+        template<typename ValueType> 
+          Any(const ValueType &t_value)
+        {
+          m_data = std::shared_ptr<Data>(new Data_Impl<ValueType>(t_value));
+        }
+
+        Any & operator=(const Any &t_any)
+        {
+          Any copy(t_any);
+          swap(copy);
+          return *this; 
+        }
+
+        template<typename ValueType> 
+          Any & operator=(const ValueType &t_value)
+        {
+          m_data = std::shared_ptr<Data>(new Data_Impl<ValueType>(t_value));
+          return *this;
+        }
+
+        template<typename ToType>
+          ToType &cast() const
+          {
+            if (typeid(ToType) == m_data->type())
+            {
+              return *static_cast<ToType *>(m_data->data());
+            } else {
+              throw chaiscript::detail::exception::bad_any_cast();
+            }
+ 
+          }
+
+
+        ~Any()
+        {
+        }
+
+        // modifiers
+        Any & swap(Any &t_other)
+        {
+          std::shared_ptr<Data> data = t_other.m_data;
+          t_other.m_data = m_data;
+          m_data = data;
+          return *this;
+        }
+
+        // queries
+        bool empty() const
+        {
+          return !bool(m_data);
+        }
+
+        const std::type_info & type() const
+        {
+          if (m_data)
+          {
+            return m_data->type();
+          } else {
+            return typeid(void);
+          }
+        }
+    };
+
+  }
+}
+
+#endif
+
+

include/chaiscript/dispatchkit/boxed_cast.hpp

@@ -13,7 +13,6 @@
 #include "dynamic_cast_conversion.hpp"
 
 #include "../chaiscript_threading.hpp"
-#include <boost/any.hpp>
 
 namespace chaiscript 
 {
@@ -65,7 +64,7 @@ namespace chaiscript
   {
     try {
       return detail::Cast_Helper<Type>::cast(bv);
-    } catch (const boost::bad_any_cast &) {
+    } catch (const chaiscript::detail::exception::bad_any_cast &) {
 
 #ifdef BOOST_MSVC
       //Thank you MSVC, yes we know that a constant value is being used in the if
@@ -80,7 +79,7 @@ namespace chaiscript
           // We will not catch any bad_boxed_dynamic_cast that is thrown, let the user get it
           // either way, we are not responsible if it doesn't work
           return detail::Cast_Helper<Type>::cast(detail::boxed_dynamic_cast<Type>(bv));
-        } catch (const boost::bad_any_cast &) {
+        } catch (const chaiscript::detail::exception::bad_any_cast &) {
           throw exception::bad_boxed_cast(bv.get_type_info(), typeid(Type));
         }
       } else {

include/chaiscript/dispatchkit/boxed_cast_helper.hpp

@@ -10,7 +10,6 @@
 #include "type_info.hpp"
 #include "boxed_value.hpp"
 
-#include <boost/any.hpp>
 
 namespace chaiscript 
 {
@@ -32,16 +31,16 @@ namespace chaiscript
           {
             if (!ob.get_type_info().is_const())
             {
-              return std::cref((boost::any_cast<std::reference_wrapper<Result> >(ob.get())).get());
+              return std::cref((ob.get().cast<std::reference_wrapper<Result> >()).get());
             } else {
-              return boost::any_cast<std::reference_wrapper<const Result> >(ob.get());
+              return ob.get().cast<std::reference_wrapper<const Result> >();
             }
           } else {
             if (!ob.get_type_info().is_const())
             {
-              return std::cref(*(boost::any_cast<std::shared_ptr<Result> >(ob.get())));   
+              return std::cref(*(ob.get().cast<std::shared_ptr<Result> >()));   
             } else {
-              return std::cref(*(boost::any_cast<std::shared_ptr<const Result> >(ob.get())));   
+              return std::cref(*(ob.get().cast<std::shared_ptr<const Result> >()));   
             }
           }
         }
@@ -74,16 +73,16 @@ namespace chaiscript
           {
             if (!ob.get_type_info().is_const())
             {
-              return &(boost::any_cast<std::reference_wrapper<Result> >(ob.get())).get();
+              return &(ob.get().cast<std::reference_wrapper<Result> >()).get();
             } else {
-              return &(boost::any_cast<std::reference_wrapper<const Result> >(ob.get())).get();
+              return &(ob.get().cast<std::reference_wrapper<const Result> >()).get();
             }
           } else {
             if (!ob.get_type_info().is_const())
             {
-              return (boost::any_cast<std::shared_ptr<Result> >(ob.get())).get();
+              return (ob.get().cast<std::shared_ptr<Result> >()).get();
             } else {
-              return (boost::any_cast<std::shared_ptr<const Result> >(ob.get())).get();
+              return (ob.get().cast<std::shared_ptr<const Result> >()).get();
             }
           }
         }
@@ -101,9 +100,9 @@ namespace chaiscript
         {
           if (ob.is_ref())
           {
-            return &(boost::any_cast<std::reference_wrapper<Result> >(ob.get())).get();
+            return &(ob.get().cast<std::reference_wrapper<Result> >()).get();
           } else {
-            return (boost::any_cast<std::shared_ptr<Result> >(ob.get())).get();
+            return (ob.get().cast<std::shared_ptr<Result> >()).get();
           }
         }
       };
@@ -120,9 +119,9 @@ namespace chaiscript
         {
           if (ob.is_ref())
           {
-            return boost::any_cast<std::reference_wrapper<Result> >(ob.get());
+            return ob.get().cast<std::reference_wrapper<Result> >();
           } else {
-            Result &r = *(boost::any_cast<std::shared_ptr<Result> >(ob.get()));
+            Result &r = *(ob.get().cast<std::shared_ptr<Result> >());
             return r;
           }
         }
@@ -138,7 +137,7 @@ namespace chaiscript
 
         static Result_Type cast(const Boxed_Value &ob)
         {
-          return boost::any_cast<std::shared_ptr<Result> >(ob.get());
+          return ob.get().cast<std::shared_ptr<Result> >();
         }
       };
 
@@ -154,9 +153,9 @@ namespace chaiscript
         {
           if (!ob.get_type_info().is_const())
           {
-            return std::const_pointer_cast<const Result>(boost::any_cast<std::shared_ptr<Result> >(ob.get()));
+            return std::const_pointer_cast<const Result>(ob.get().cast<std::shared_ptr<Result> >());
           } else {
-            return boost::any_cast<std::shared_ptr<const Result> >(ob.get());
+            return ob.get().cast<std::shared_ptr<const Result> >();
           }
         }
       };

include/chaiscript/dispatchkit/boxed_number.hpp

@@ -38,9 +38,9 @@ namespace chaiscript
             case Operators::not_equal:
               return const_var(t != u);
             default:
-              throw boost::bad_any_cast();        
+              throw chaiscript::detail::exception::bad_any_cast();        
           }
-          throw boost::bad_any_cast();        
+          throw chaiscript::detail::exception::bad_any_cast();        
         }
       };
 
@@ -73,7 +73,7 @@ namespace chaiscript
               t -= u;
               break;
             default:
-              throw boost::bad_any_cast();        
+              throw chaiscript::detail::exception::bad_any_cast();        
           }
 
           return t_lhs;
@@ -106,7 +106,7 @@ namespace chaiscript
               t ^= u;
               break;
             default:
-              throw boost::bad_any_cast();        
+              throw chaiscript::detail::exception::bad_any_cast();        
           }
           return t_lhs;
         }
@@ -134,9 +134,9 @@ namespace chaiscript
             case Operators::bitwise_complement:
               return const_var(~t);
             default:
-              throw boost::bad_any_cast();        
+              throw chaiscript::detail::exception::bad_any_cast();        
           }
-          throw boost::bad_any_cast();        
+          throw chaiscript::detail::exception::bad_any_cast();        
         }
       };
 
@@ -160,9 +160,9 @@ namespace chaiscript
             case Operators::unary_plus:
               return const_var(+t);
             default:
-              throw boost::bad_any_cast();        
+              throw chaiscript::detail::exception::bad_any_cast();        
           }
-          throw boost::bad_any_cast();        
+          throw chaiscript::detail::exception::bad_any_cast();        
         }
       };
 
@@ -183,7 +183,7 @@ namespace chaiscript
           } else if (t_oper > Operators::const_flag) {
             return const_binary::go<LHS, RHS>(t_oper, *static_cast<const LHS *>(t_lhs.get_const_ptr()), *static_cast<const RHS *>(t_rhs.get_const_ptr()), t_lhs);
           } else {
-            throw boost::bad_any_cast();
+            throw chaiscript::detail::exception::bad_any_cast();
           }
         }
       };
@@ -199,13 +199,13 @@ namespace chaiscript
           } else if (t_oper > Operators::non_const_flag && t_oper < Operators::non_const_int_flag && !t_lhs.is_const()) {
             return binary::go<LHS, RHS>(t_oper, *static_cast<LHS *>(t_lhs.get_ptr()), *static_cast<const RHS *>(t_rhs.get_const_ptr()), t_lhs);
           } else if (t_oper > Operators::non_const_int_flag && t_oper < Operators::const_int_flag) {
-            throw boost::bad_any_cast();
+            throw chaiscript::detail::exception::bad_any_cast();
           } else if (t_oper > Operators::const_int_flag && t_oper < Operators::const_flag) {
-            throw boost::bad_any_cast();
+            throw chaiscript::detail::exception::bad_any_cast();
           } else if (t_oper > Operators::const_flag) {
             return const_binary::go<LHS, RHS>(t_oper, *static_cast<const LHS *>(t_lhs.get_const_ptr()), *static_cast<const RHS *>(t_rhs.get_const_ptr()), t_lhs);
           } else {
-            throw boost::bad_any_cast();
+            throw chaiscript::detail::exception::bad_any_cast();
           }
         }
       };
@@ -248,7 +248,7 @@ namespace chaiscript
           } else if (inp_ == typeid(std::uint64_t)) {
             return Go<LHS, std::uint64_t, Float>::go(t_oper, t_lhs, t_rhs);
           } else {
-            throw boost::bad_any_cast();
+            throw chaiscript::detail::exception::bad_any_cast();
           }
         } 
 
@@ -289,7 +289,7 @@ namespace chaiscript
           } else if (inp_ == typeid(std::uint64_t)) {
             return oper_rhs<std::uint64_t, false>(t_oper, t_lhs, t_rhs);
           } else  {
-            throw boost::bad_any_cast();
+            throw chaiscript::detail::exception::bad_any_cast();
           }
         }
       
@@ -302,12 +302,12 @@ namespace chaiscript
         const Type_Info &inp_ = v.get_type_info();
         if (inp_ == typeid(bool))
         {
-          throw boost::bad_any_cast();
+          throw chaiscript::detail::exception::bad_any_cast();
         }
 
         if (!inp_.is_arithmetic())
         {
-          throw boost::bad_any_cast();
+          throw chaiscript::detail::exception::bad_any_cast();
         }
       }
 

include/chaiscript/dispatchkit/boxed_value.hpp

@@ -12,7 +12,7 @@
 #include "../chaiscript_threading.hpp"
 
 #include <map>
-#include <boost/any.hpp>
+#include "any.hpp"
 
 namespace chaiscript 
 {
@@ -36,7 +36,7 @@ namespace chaiscript
       struct Data
       {
         Data(const Type_Info &ti,
-            const boost::any &to,
+            const chaiscript::detail::Any &to,
             bool tr,
             const void *t_void_ptr)
           : m_type_info(ti), m_obj(to), m_data_ptr(ti.is_const()?0:const_cast<void *>(t_void_ptr)), m_const_data_ptr(t_void_ptr),
@@ -60,7 +60,7 @@ namespace chaiscript
         }
 
         Type_Info m_type_info;
-        boost::any m_obj;
+        chaiscript::detail::Any m_obj;
         void *m_data_ptr;
         const void *m_const_data_ptr;
         bool m_is_ref;
@@ -73,7 +73,7 @@ namespace chaiscript
         {
           return std::shared_ptr<Data> (new Data(
                 detail::Get_Type_Info<void>::get(),
-                boost::any(), 
+                chaiscript::detail::Any(), 
                 false,
                 0)
               );
@@ -90,7 +90,7 @@ namespace chaiscript
           {
             return std::shared_ptr<Data>(new Data(
                   detail::Get_Type_Info<T>::get(), 
-                  boost::any(obj), 
+                  chaiscript::detail::Any(obj), 
                   false,
                   obj.get())
                 );
@@ -107,7 +107,7 @@ namespace chaiscript
           {
             return std::shared_ptr<Data>(new Data(
                   detail::Get_Type_Info<T>::get(),
-                  boost::any(obj),
+                  chaiscript::detail::Any(obj),
                   true,
                   &obj.get())
                 );
@@ -119,7 +119,7 @@ namespace chaiscript
             std::shared_ptr<T> p(new T(t));
             return std::shared_ptr<Data>(new Data(
                   detail::Get_Type_Info<T>::get(), 
-                  boost::any(p), 
+                  chaiscript::detail::Any(p), 
                   false,
                   p.get())
                 );
@@ -129,7 +129,7 @@ namespace chaiscript
         {
           return std::shared_ptr<Data> (new Data(
                 Type_Info(),
-                boost::any(),
+                chaiscript::detail::Any(),
                 false,
                 0)
               );
@@ -220,7 +220,7 @@ namespace chaiscript
         return (m_data->m_data_ptr == 0 && m_data->m_const_data_ptr == 0);
       }
 
-      const boost::any & get() const
+      const chaiscript::detail::Any & get() const
       {
         return m_data->m_obj;
       }

include/chaiscript/dispatchkit/dispatchkit.hpp

@@ -100,7 +100,7 @@ namespace chaiscript
       {
         if (!t_bv.is_const())
         {
-          throw exception::global_non_const();
+          throw chaiscript::exception::global_non_const();
         }
 
         m_globals.push_back(std::make_pair(t_bv, t_name));
@@ -421,7 +421,7 @@ namespace chaiscript
           validate_object_name(name);
           if (!obj.is_const())
           {
-            throw exception::global_non_const();
+            throw chaiscript::exception::global_non_const();
           }
 
           chaiscript::detail::threading::unique_lock<chaiscript::detail::threading::shared_mutex> l(m_global_object_mutex);
@@ -928,7 +928,7 @@ namespace chaiscript
 
           if (m_state.m_reserved_words.find(name) != m_state.m_reserved_words.end())
           {
-            throw exception::reserved_word_error(name);
+            throw chaiscript::exception::reserved_word_error(name);
           }
         }
 

include/chaiscript/dispatchkit/dynamic_cast_conversion.hpp

@@ -117,7 +117,7 @@ namespace chaiscript
               }
             }
           } else {
-            throw exception::bad_boxed_dynamic_cast(t_derived.get_type_info(), typeid(Base), "Unknown dynamic_cast_conversion");
+            throw chaiscript::exception::bad_boxed_dynamic_cast(t_derived.get_type_info(), typeid(Base), "Unknown dynamic_cast_conversion");
           }
         }
     };
@@ -272,9 +272,9 @@ namespace chaiscript
         try {
           return detail::Dynamic_Conversions::get().get_conversion(user_type<Base>(), derived.get_type_info())->convert(derived);
         } catch (const std::out_of_range &) {
-          throw exception::bad_boxed_dynamic_cast(derived.get_type_info(), typeid(Base), "No known conversion");
+          throw chaiscript::exception::bad_boxed_dynamic_cast(derived.get_type_info(), typeid(Base), "No known conversion");
         } catch (const std::bad_cast &) {
-          throw exception::bad_boxed_dynamic_cast(derived.get_type_info(), typeid(Base), "Unable to perform dynamic_cast operation");
+          throw chaiscript::exception::bad_boxed_dynamic_cast(derived.get_type_info(), typeid(Base), "Unable to perform dynamic_cast operation");
         }
       }
   }

include/chaiscript/dispatchkit/exception_specification.hpp

@@ -21,7 +21,7 @@ namespace chaiscript
         template<typename T>
         void throw_type(const Boxed_Value &bv)
         {
-          try { T t = boxed_cast<T>(bv); throw t; } catch (const exception::bad_boxed_cast &) {}
+          try { T t = boxed_cast<T>(bv); throw t; } catch (const chaiscript::exception::bad_boxed_cast &) {}
         }
     };
 

include/chaiscript/language/chaiscript_engine.hpp

@@ -57,7 +57,7 @@ namespace chaiscript
         {
           if (!m_data)
           {
-            throw exception::load_module_error(dlerror());
+            throw chaiscript::exception::load_module_error(dlerror());
           }
         }
 
@@ -80,7 +80,7 @@ namespace chaiscript
           {
             if (!m_symbol)
             {
-              throw exception::load_module_error(dlerror());
+              throw chaiscript::exception::load_module_error(dlerror());
             }
           }
 
@@ -180,7 +180,7 @@ namespace chaiscript
         {
           if (!m_data)
           {
-            throw exception::load_module_error(GetErrorMessage(GetLastError()));
+            throw chaiscript::exception::load_module_error(GetErrorMessage(GetLastError()));
           }
         }
 
@@ -200,7 +200,7 @@ namespace chaiscript
           {
             if (!m_symbol)
             {
-              throw exception::load_module_error(GetErrorMessage(GetLastError()));
+              throw chaiscript::exception::load_module_error(GetErrorMessage(GetLastError()));
             }
           }
 
@@ -223,7 +223,7 @@ namespace chaiscript
     {
       Loadable_Module(const std::string &, const std::string &)
       {
-        throw exception::load_module_error("Loadable module support not available for your platform");
+        throw chaiscript::exception::load_module_error("Loadable module support not available for your platform");
       }
 
       ModulePtr m_moduleptr;
@@ -302,10 +302,10 @@ namespace chaiscript
             l2.unlock();
             eval_file(appendedpath);
           }
-        } catch (const exception::file_not_found_error &) {
+        } catch (const chaiscript::exception::file_not_found_error &) {
           if (i == m_usepaths.size() - 1)
           {
-            throw exception::file_not_found_error(t_filename);
+            throw chaiscript::exception::file_not_found_error(t_filename);
           }
 
           // failed to load, try the next path
@@ -378,7 +378,7 @@ namespace chaiscript
       std::ifstream infile(t_filename.c_str(), std::ios::in | std::ios::ate | std::ios::binary );
 
       if (!infile.is_open()) {
-        throw exception::file_not_found_error(t_filename);
+        throw chaiscript::exception::file_not_found_error(t_filename);
       }
 
       std::streampos size = infile.tellg();
@@ -420,7 +420,7 @@ namespace chaiscript
     /// \brief Adds a constant object that is available in all contexts and to all threads
     /// \param[in] t_bv Boxed_Value to add as a global
     /// \param[in] t_name Name of the value to add
-    /// \throw exception::global_non_const If t_bv is not a constant object
+    /// \throw chaiscript::exception::global_non_const If t_bv is not a constant object
     /// \sa Boxed_Value::is_const
     ChaiScript &add_global_const(const Boxed_Value &t_bv, const std::string &t_name)
     {
@@ -536,7 +536,7 @@ namespace chaiscript
     /// If no file can be found matching the search criteria and containing the appropriate entry point 
     /// (the symbol mentioned above), an exception is thrown.
     ///
-    /// \throw exception::load_module_error In the event that no matching module can be found.
+    /// \throw chaiscript::exception::load_module_error In the event that no matching module can be found.
     void load_module(const std::string &t_module_name)
     {
       std::vector<exception::load_module_error> errors;
@@ -560,7 +560,7 @@ namespace chaiscript
                     std::string name = m_modulepaths[i] + prefixes[j] + t_module_name + postfixes[k];
                     load_module(t_module_name, name);
                     return;
-                  } catch (const exception::load_module_error &e) {
+                  } catch (const chaiscript::exception::load_module_error &e) {
                     errors.push_back(e);
                     // Try next set
                   }
@@ -582,7 +582,7 @@ namespace chaiscript
         errstring += itr->what();
       }
 
-      throw exception::load_module_error("Unable to find module: " + t_module_name + " Errors: " + errstring);
+      throw chaiscript::exception::load_module_error("Unable to find module: " + t_module_name + " Errors: " + errstring);
     }
 
     /// \brief Load a binary module from a dynamic library. Works on platforms that support
@@ -616,7 +616,7 @@ namespace chaiscript
     ///
     /// \return result of the script execution
     /// 
-    /// \throw exception::eval_error In the case that evaluation fails.
+    /// \throw chaiscript::exception::eval_error In the case that evaluation fails.
     Boxed_Value operator()(const std::string &t_script, const Exception_Handler &t_handler = Exception_Handler())
     {
       try {
@@ -637,8 +637,8 @@ namespace chaiscript
     ///
     /// \return result of the script execution
     /// 
-    /// \throw exception::eval_error In the case that evaluation fails.
-    /// \throw exception::bad_boxed_cast In the case that evaluation succeeds but the result value cannot be converted
+    /// \throw chaiscript::exception::eval_error In the case that evaluation fails.
+    /// \throw chaiscript::exception::bad_boxed_cast In the case that evaluation succeeds but the result value cannot be converted
     ///        to the requested type.
     template<typename T>
     T eval(const std::string &t_input, const Exception_Handler &t_handler = Exception_Handler())
@@ -660,7 +660,7 @@ namespace chaiscript
     ///
     /// \return result of the script execution
     /// 
-    /// \throw exception::eval_error In the case that evaluation fails.
+    /// \throw chaiscript::exception::eval_error In the case that evaluation fails.
     Boxed_Value eval(const std::string &t_input, const Exception_Handler &t_handler = Exception_Handler())
     {
       try {
@@ -677,7 +677,7 @@ namespace chaiscript
     /// \param[in] t_filename File to load and parse.
     /// \param[in] t_handler Optional Exception_Handler used for automatic unboxing of script thrown exceptions
     /// \return result of the script execution
-    /// \throw exception::eval_error In the case that evaluation fails.
+    /// \throw chaiscript::exception::eval_error In the case that evaluation fails.
     Boxed_Value eval_file(const std::string &t_filename, const Exception_Handler &t_handler = Exception_Handler()) {
       try {
         return do_eval(load_file(t_filename), t_filename);
@@ -694,8 +694,8 @@ namespace chaiscript
     /// \param[in] t_filename File to load and parse.
     /// \param[in] t_handler Optional Exception_Handler used for automatic unboxing of script thrown exceptions
     /// \return result of the script execution
-    /// \throw exception::eval_error In the case that evaluation fails.
-    /// \throw exception::bad_boxed_cast In the case that evaluation succeeds but the result value cannot be converted
+    /// \throw chaiscript::exception::eval_error In the case that evaluation fails.
+    /// \throw chaiscript::exception::bad_boxed_cast In the case that evaluation succeeds but the result value cannot be converted
     ///        to the requested type.
     template<typename T>
     T eval_file(const std::string &t_filename, const Exception_Handler &t_handler = Exception_Handler()) {