/* -*- C++ -*-

  *

  * This file is a part of LEMON, a generic C++ optimization library

  *

  * Copyright (C) 2003-2006

  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

  * (Egervary Research Group on Combinatorial Optimization, EGRES).

  *

  * Permission to use, modify and distribute this software is granted

  * provided that this copyright notice appears in all copies. For

  * precise terms see the accompanying LICENSE file.

  *

  * This software is provided "AS IS" with no warranty of any kind,

  * express or implied, and with no claim as to its suitability for any

  * purpose.

  *

  */

 #ifndef LEMON_BITS_VARIANT_H

 #define LEMON_BITS_VARIANT_H

 #include <lemon/error.h>

 namespace lemon {

   template <bool left, bool right>

   struct CTOr {

     static const bool value = true;

   };

   template <>

   struct CTOr<false, false> {

     static const bool value = false;

   };

   template <bool left, bool right>

   struct CTAnd {

     static const bool value = false;

   };

   template <>

   struct CTAnd<true, true> {

     static const bool value = true;

   };

   template <int left, int right>

   struct CTEqual {

     static const bool value = false;

   };

   template <int val>

   struct CTEqual<val, val> {

     static const bool value = true;

   };

   template <int left, int right>

   struct CTLess {

     static const bool value = left < right;

   };

   template <int left>

   struct CTLess<left, 0> {

     static const bool value = false;

   };

   template <int right>

   struct CTLess<0, right> {

     static const bool value = true;

   };

   template <>

   struct CTLess<0, 0> {

     static const bool value = false;

   };

   template <>

   struct CTLess<1, 1> {

     static const bool value = false;

   };

   template <bool less, int left, int right>

   struct CTMaxImpl {

     static const int value = left;    

   };

   template <int left, int right>

   struct CTMaxImpl<true, left, right> {

     static const int value = right;

   };

   template <int left, int right>

   struct CTMax {

     static const int value = 

     CTMaxImpl<CTLess<left, right>::value, left, right>::value;

   };

   /// \brief Simple Variant type with two type

   ///

   /// Simple Variant type with two type

   template <typename _First, typename _Second>

   class BiVariant {

   public:

     typedef _First First;

     typedef _Second Second;

     struct WrongStateError : public lemon::LogicError {

     public:

       virtual const char* what() const throw() {

         return "lemon::BiVariant::WrongStateError";

       }

     };

     BiVariant() {

       flag = true;

       new(reinterpret_cast<First*>(data)) First();

     }

     BiVariant(const First& first) {

       flag = true;

       new(reinterpret_cast<First*>(data)) First(first);

     }

     BiVariant(const Second& second) {

       flag = false;

       new(reinterpret_cast<Second*>(data)) Second(second);

     }

     BiVariant(const BiVariant& bivariant) {

       flag = bivariant.flag;

       if (flag) {

         new(reinterpret_cast<First*>(data)) First(bivariant.first());      

       } else {

         new(reinterpret_cast<Second*>(data)) Second(bivariant.second());      

       }

     }

     ~BiVariant() {

       destroy();

     }

     BiVariant& setFirst() {

       destroy();

       flag = true;

       new(reinterpret_cast<First*>(data)) First();   

       return *this;

     }

     BiVariant& setFirst(const First& first) {

       destroy();

       flag = true;

       new(reinterpret_cast<First*>(data)) First(first);   

       return *this;

     }

     BiVariant& setSecond() {

       destroy();

       flag = false;

       new(reinterpret_cast<Second*>(data)) Second();   

       return *this;

     }

     BiVariant& setSecond(const Second& second) {

       destroy();

       flag = false;

       new(reinterpret_cast<Second*>(data)) Second(second);   

       return *this;

     }

     BiVariant& operator=(const First& first) {

       return setFirst(first);

     }

     BiVariant& operator=(const Second& second) {

       return setSecond(second);

     }

     BiVariant& operator=(const BiVariant& bivariant) {

       if (this == &bivariant) return *this;

       destroy();

       flag = bivariant.flag;

       if (flag) {

         new(reinterpret_cast<First*>(data)) First(bivariant.first());      

       } else {

         new(reinterpret_cast<Second*>(data)) Second(bivariant.second());      

       }

       return *this;

     }

     First& first() {

       LEMON_ASSERT(flag, WrongStateError());

       return *reinterpret_cast<First*>(data); 

     }

     const First& first() const { 

       LEMON_ASSERT(flag, WrongStateError());

       return *reinterpret_cast<const First*>(data); 

     }

     operator First&() { return first(); }

     operator const First&() const { return first(); }

     Second& second() { 

       LEMON_ASSERT(!flag, WrongStateError());

       return *reinterpret_cast<Second*>(data); 

     }

     const Second& second() const { 

       LEMON_ASSERT(!flag, WrongStateError());

       return *reinterpret_cast<const Second*>(data); 

     }

     operator Second&() { return second(); }

     operator const Second&() const { return second(); }

     bool firstState() const { return flag; }

     bool secondState() const { return !flag; }

   private:

     void destroy() {

       if (flag) {

         reinterpret_cast<First*>(data)->~First();

       } else {

         reinterpret_cast<Second*>(data)->~Second();

       }

     }

     char data[CTMax<sizeof(First), sizeof(Second)>::value];

     bool flag;

   };

 }

 #endif