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+////////////////////////////////////////////////////////////////////////////////
+// The Loki Library
+// Copyright (c) 2001 by Andrei Alexandrescu
+// This code accompanies the book:
+// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design 
+//     Patterns Applied". Copyright (c) 2001. Addison-Wesley.
+// Permission to use, copy, modify, distribute and sell this software for any 
+//     purpose is hereby granted without fee, provided that the above copyright 
+//     notice appear in all copies and that both that copyright notice and this 
+//     permission notice appear in supporting documentation.
+// The author or Addison-Wesley Longman make no representations about the 
+//     suitability of this software for any purpose. It is provided "as is" 
+//     without express or implied warranty.
+////////////////////////////////////////////////////////////////////////////////
+#ifndef LOKI_MULTIMETHODS_INC_
+#define LOKI_MULTIMETHODS_INC_
+
+// $Id: MultiMethods.h 751 2006-10-17 19:50:37Z syntheticpp $
+
+
+#include "Typelist.h"
+#include "LokiTypeInfo.h"
+#include "Functor.h"
+#include "AssocVector.h"
+
+////////////////////////////////////////////////////////////////////////////////
+// IMPORTANT NOTE:
+// The double dispatchers implemented below differ from the excerpts shown in
+// the book - they are simpler while respecting the same interface.
+////////////////////////////////////////////////////////////////////////////////
+
+namespace Loki
+{
+////////////////////////////////////////////////////////////////////////////////
+// class template InvocationTraits (helper)
+// Helps implementing optional symmetry
+////////////////////////////////////////////////////////////////////////////////
+
+    namespace Private
+    {
+        template <class SomeLhs, class SomeRhs, 
+            class Executor, typename ResultType>
+        struct InvocationTraits
+        {
+            static ResultType 
+        DoDispatch(SomeLhs& lhs, SomeRhs& rhs, 
+            Executor& exec, Int2Type<false>)
+            {
+                return exec.Fire(lhs, rhs);
+            }
+            static ResultType 
+        DoDispatch(SomeLhs& lhs, SomeRhs& rhs, 
+            Executor& exec, Int2Type<true>)
+            {
+                return exec.Fire(rhs, lhs);
+            }
+        };
+    }
+
+////////////////////////////////////////////////////////////////////////////////
+// class template StaticDispatcher
+// Implements an automatic static double dispatcher based on two typelists
+////////////////////////////////////////////////////////////////////////////////
+
+    template
+    <
+        class Executor,
+        class BaseLhs, 
+        class TypesLhs,
+        bool symmetric = true,
+        class BaseRhs = BaseLhs,
+        class TypesRhs = TypesLhs,
+        typename ResultType = void
+    >
+    class StaticDispatcher
+    {
+        template <class SomeLhs>
+        static ResultType DispatchRhs(SomeLhs& lhs, BaseRhs& rhs,
+            Executor exec, NullType)
+        { return exec.OnError(lhs, rhs); }
+        
+        template <class Head, class Tail, class SomeLhs>
+        static ResultType DispatchRhs(SomeLhs& lhs, BaseRhs& rhs,
+            Executor exec, Typelist<Head, Tail>)
+        {            
+            if (Head* p2 = dynamic_cast<Head*>(&rhs))
+            {
+                Int2Type<(symmetric &&
+                          int(TL::IndexOf<TypesRhs, Head>::value) <
+                          int(TL::IndexOf<TypesLhs, SomeLhs>::value))> i2t;
+
+                typedef Private::InvocationTraits< 
+                        SomeLhs, Head, Executor, ResultType> CallTraits;
+                    
+                return CallTraits::DoDispatch(lhs, *p2, exec, i2t);
+            }
+            return DispatchRhs(lhs, rhs, exec, Tail());
+        }
+        
+        static ResultType DispatchLhs(BaseLhs& lhs, BaseRhs& rhs,
+            Executor exec, NullType)
+        { return exec.OnError(lhs, rhs); }
+        
+        template <class Head, class Tail>
+        static ResultType DispatchLhs(BaseLhs& lhs, BaseRhs& rhs,
+            Executor exec, Typelist<Head, Tail>)
+        {            
+            if (Head* p1 = dynamic_cast<Head*>(&lhs))
+            {
+                return DispatchRhs(*p1, rhs, exec, TypesRhs());
+            }
+            return DispatchLhs(lhs, rhs, exec, Tail());
+        }
+
+    public:
+        static ResultType Go(BaseLhs& lhs, BaseRhs& rhs,
+            Executor exec)
+        { return DispatchLhs(lhs, rhs, exec, TypesLhs()); }
+    };
+    
+////////////////////////////////////////////////////////////////////////////////
+// class template BasicDispatcher
+// Implements a logarithmic double dispatcher for functors (or functions)
+// Doesn't offer automated casts or symmetry
+////////////////////////////////////////////////////////////////////////////////
+
+    template
+    <
+        class BaseLhs,
+        class BaseRhs = BaseLhs,
+        typename ResultType = void,
+        typename CallbackType = ResultType (*)(BaseLhs&, BaseRhs&)
+    >
+    class BasicDispatcher
+    {
+        typedef std::pair<TypeInfo,TypeInfo> KeyType;
+        typedef CallbackType MappedType;
+        typedef AssocVector<KeyType, MappedType> MapType;
+        MapType callbackMap_;
+        
+        void DoAdd(TypeInfo lhs, TypeInfo rhs, CallbackType fun);
+        bool DoRemove(TypeInfo lhs, TypeInfo rhs);
+        
+    public:
+        template <class SomeLhs, class SomeRhs>
+        void Add(CallbackType fun)
+        {
+            DoAdd(typeid(SomeLhs), typeid(SomeRhs), fun);
+        }
+        
+        template <class SomeLhs, class SomeRhs>
+        bool Remove()
+        {
+            return DoRemove(typeid(SomeLhs), typeid(SomeRhs));
+        }
+        
+        ResultType Go(BaseLhs& lhs, BaseRhs& rhs);
+    };
+
+    // Non-inline to reduce compile time overhead...
+    template <class BaseLhs, class BaseRhs, 
+        typename ResultType, typename CallbackType>
+    void BasicDispatcher<BaseLhs,BaseRhs,ResultType,CallbackType>
+         ::DoAdd(TypeInfo lhs, TypeInfo rhs, CallbackType fun)
+    {
+        callbackMap_[KeyType(lhs, rhs)] = fun;
+    }
+        
+    template <class BaseLhs, class BaseRhs, 
+        typename ResultType, typename CallbackType>
+    bool BasicDispatcher<BaseLhs,BaseRhs,ResultType,CallbackType>
+         ::DoRemove(TypeInfo lhs, TypeInfo rhs)
+    {
+        return callbackMap_.erase(KeyType(lhs, rhs)) == 1;
+    }
+
+    template <class BaseLhs, class BaseRhs, 
+        typename ResultType, typename CallbackType>
+    ResultType BasicDispatcher<BaseLhs,BaseRhs,ResultType,CallbackType>
+               ::Go(BaseLhs& lhs, BaseRhs& rhs)
+    {
+        typename MapType::key_type k(typeid(lhs),typeid(rhs));
+        typename MapType::iterator i = callbackMap_.find(k);
+        if (i == callbackMap_.end())
+        {
+                throw std::runtime_error("Function not found");
+        }
+        return (i->second)(lhs, rhs);
+    }
+
+////////////////////////////////////////////////////////////////////////////////
+// class template StaticCaster
+// Implementation of the CastingPolicy used by FunctorDispatcher
+////////////////////////////////////////////////////////////////////////////////
+
+    template <class To, class From>
+    struct StaticCaster
+    {
+        static To& Cast(From& obj)
+        {
+            return static_cast<To&>(obj);
+        }
+    };
+
+////////////////////////////////////////////////////////////////////////////////
+// class template DynamicCaster
+// Implementation of the CastingPolicy used by FunctorDispatcher
+////////////////////////////////////////////////////////////////////////////////
+
+    template <class To, class From>
+    struct DynamicCaster
+    {
+        static To& Cast(From& obj)
+        {
+            return dynamic_cast<To&>(obj);
+        }
+    };
+
+////////////////////////////////////////////////////////////////////////////////
+// class template Private::FnDispatcherHelper
+// Implements trampolines and argument swapping used by FnDispatcher
+////////////////////////////////////////////////////////////////////////////////
+
+    namespace Private
+    {
+        template <class BaseLhs, class BaseRhs,
+        class SomeLhs, class SomeRhs,
+            typename ResultType,
+            class CastLhs, class CastRhs,
+            ResultType (*Callback)(SomeLhs&, SomeRhs&)>
+        struct FnDispatcherHelper
+        {
+            static ResultType Trampoline(BaseLhs& lhs, BaseRhs& rhs)
+            {
+                return Callback(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
+            }
+            static ResultType TrampolineR(BaseRhs& rhs, BaseLhs& lhs)
+            {
+                return Trampoline(lhs, rhs);
+            }
+        };
+    }
+
+////////////////////////////////////////////////////////////////////////////////
+// class template FnDispatcher
+// Implements an automatic logarithmic double dispatcher for functions
+// Features automated conversions
+////////////////////////////////////////////////////////////////////////////////
+
+    template <class BaseLhs, class BaseRhs = BaseLhs,
+              typename ResultType = void,
+              template <class, class> class CastingPolicy = DynamicCaster,
+              template <class, class, class, class>
+              class DispatcherBackend = BasicDispatcher>
+    class FnDispatcher
+    {
+        DispatcherBackend<BaseLhs, BaseRhs, ResultType, 
+            ResultType (*)(BaseLhs&, BaseRhs&)> backEnd_;
+        
+    public:
+        template <class SomeLhs, class SomeRhs>
+        void Add(ResultType (*pFun)(BaseLhs&, BaseRhs&))
+        {
+            return backEnd_.template Add<SomeLhs, SomeRhs>(pFun);
+        }        
+        
+        template <class SomeLhs, class SomeRhs,
+            ResultType (*callback)(SomeLhs&, SomeRhs&)>
+        void Add()
+        {
+        typedef Private::FnDispatcherHelper<
+                    BaseLhs, BaseRhs, 
+                    SomeLhs, SomeRhs,
+                    ResultType,
+                    CastingPolicy<SomeLhs,BaseLhs>, 
+                    CastingPolicy<SomeRhs,BaseRhs>, 
+                    callback> Local;
+
+            Add<SomeLhs, SomeRhs>(&Local::Trampoline);
+        }
+        
+        template <class SomeLhs, class SomeRhs,
+            ResultType (*callback)(SomeLhs&, SomeRhs&),
+            bool symmetric>
+        void Add(bool = true) // [gcc] dummy bool
+        {
+        typedef Private::FnDispatcherHelper<
+                    BaseLhs, BaseRhs, 
+                    SomeLhs, SomeRhs,
+                    ResultType,
+                    CastingPolicy<SomeLhs,BaseLhs>, 
+                    CastingPolicy<SomeRhs,BaseRhs>, 
+                    callback> Local;
+
+            Add<SomeLhs, SomeRhs>(&Local::Trampoline);
+            if (symmetric)
+            {
+                Add<SomeRhs, SomeLhs>(&Local::TrampolineR);
+            }
+        }
+        
+        template <class SomeLhs, class SomeRhs>
+        void Remove()
+        {
+            backEnd_.template Remove<SomeLhs, SomeRhs>();
+        }
+
+        ResultType Go(BaseLhs& lhs, BaseRhs& rhs)
+        {
+            return backEnd_.Go(lhs, rhs);
+        }
+    };
+
+////////////////////////////////////////////////////////////////////////////////
+// class template FunctorDispatcherAdaptor
+// permits use of FunctorDispatcher under gcc.2.95.2/3
+///////////////////////////////////////////////////////////////////////////////
+
+    namespace Private
+    {
+    template <class BaseLhs, class BaseRhs,
+          class SomeLhs, class SomeRhs,
+          typename ResultType,
+          class CastLhs, class CastRhs,
+          class Fun, bool SwapArgs>
+        class FunctorDispatcherHelper 
+        {
+            Fun fun_;
+            ResultType Fire(BaseLhs& lhs, BaseRhs& rhs,Int2Type<false>)
+            {
+                return fun_(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
+            }
+            ResultType Fire(BaseLhs& rhs, BaseRhs& lhs,Int2Type<true>)
+            {
+                return fun_(CastLhs::Cast(lhs), CastRhs::Cast(rhs));
+            }
+        public:
+            FunctorDispatcherHelper(const Fun& fun) : fun_(fun) {}
+
+            ResultType operator()(BaseLhs& lhs, BaseRhs& rhs)
+            {
+                return Fire(lhs,rhs,Int2Type<SwapArgs>());
+            }
+        };
+    }
+
+////////////////////////////////////////////////////////////////////////////////
+// class template FunctorDispatcher
+// Implements a logarithmic double dispatcher for functors
+// Features automated casting
+////////////////////////////////////////////////////////////////////////////////
+
+    template <class BaseLhs, class BaseRhs = BaseLhs,
+              typename ResultType = void,
+              template <class, class> class CastingPolicy = DynamicCaster, 
+              template <class, class, class, class>
+              class DispatcherBackend = BasicDispatcher>
+    class FunctorDispatcher
+    {
+        typedef LOKI_TYPELIST_2(BaseLhs&, BaseRhs&) ArgsList;
+        typedef Functor<ResultType, ArgsList, LOKI_DEFAULT_THREADING> FunctorType;
+
+        DispatcherBackend<BaseLhs, BaseRhs, ResultType, FunctorType> backEnd_;
+
+    public:
+        template <class SomeLhs, class SomeRhs, class Fun>
+        void Add(const Fun& fun)
+        {
+            typedef Private::FunctorDispatcherHelper<
+                    BaseLhs, BaseRhs,
+                    SomeLhs, SomeRhs,
+                    ResultType,
+                    CastingPolicy<SomeLhs, BaseLhs>,
+                    CastingPolicy<SomeRhs, BaseRhs>,
+                    Fun, false> Adapter;
+
+            backEnd_.template Add<SomeLhs, SomeRhs>(FunctorType(Adapter(fun)));
+    }
+        template <class SomeLhs, class SomeRhs, bool symmetric, class Fun>
+        void Add(const Fun& fun)
+        {
+        Add<SomeLhs,SomeRhs>(fun);
+
+        if (symmetric)
+        {
+        // Note: symmetry only makes sense where BaseLhs==BaseRhs
+                typedef Private::FunctorDispatcherHelper<
+                    BaseLhs, BaseLhs,
+                    SomeLhs, SomeRhs,
+                    ResultType,
+                    CastingPolicy<SomeLhs, BaseLhs>,
+                    CastingPolicy<SomeRhs, BaseLhs>,
+                    Fun, true> AdapterR;
+
+                backEnd_.template Add<SomeRhs, SomeLhs>(FunctorType(AdapterR(fun)));
+        }
+        }
+        
+        template <class SomeLhs, class SomeRhs>
+        void Remove()
+        {
+            backEnd_.template Remove<SomeLhs, SomeRhs>();
+        }
+
+        ResultType Go(BaseLhs& lhs, BaseRhs& rhs)
+        {
+            return backEnd_.Go(lhs, rhs);
+        }
+    };
+} // namespace Loki
+
+
+
+#endif // end file guardian
+