/* -*- 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.

  *

  */

 // This file contains a modified version of the enable_if library from BOOST.

 // See the appropriate copyright notice below.

 // Boost enable_if library

 // Copyright 2003 © The Trustees of Indiana University.

 // Use, modification, and distribution is subject to the Boost Software

 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at

 // http://www.boost.org/LICENSE_1_0.txt)

 //    Authors: Jaakko Järvi (jajarvi at osl.iu.edu)

 //             Jeremiah Willcock (jewillco at osl.iu.edu)

 //             Andrew Lumsdaine (lums at osl.iu.edu)

 #ifndef LEMON_BITS_UTILITY_H

 #define LEMON_BITS_UTILITY_H

 #include <lemon/error.h>

 ///\file

 ///\brief Miscellaneous basic utilities

 ///

 ///\todo Please rethink the organisation of the basic files like this.

 ///E.g. this file might be merged with invalid.h.

 namespace lemon

 {

   /// Basic type for defining "tags". A "YES" condition for \c enable_if.

   /// Basic type for defining "tags". A "YES" condition for \c enable_if.

   ///

   ///\sa False

   ///

   /// \todo This should go to a separate "basic_types.h" (or something)

   /// file.

   struct True {

     ///\e

     static const bool value = true;

   };

   /// Basic type for defining "tags". A "NO" condition for \c enable_if.

   /// Basic type for defining "tags". A "NO" condition for \c enable_if.

   ///

   ///\sa True

   struct False {

     ///\e

     static const bool value = false;

   };

   class InvalidType {

   private:

     InvalidType();

   };

   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;

   };

   template <typename T>

   struct Wrap {

     const T &value;

     Wrap(const T &t) : value(t) {}

   };

   /**************** dummy class to avoid ambiguity ****************/

   template<int T> struct dummy { dummy(int) {} };

   /**************** enable_if from BOOST ****************/

   template <bool B, class T = void>

   struct enable_if_c {

     typedef T type;

   };

   template <class T>

   struct enable_if_c<false, T> {};

   template <class Cond, class T = void> 

   struct enable_if : public enable_if_c<Cond::value, T> {};

   template <bool B, class T>

   struct lazy_enable_if_c {

     typedef typename T::type type;

   };

   template <class T>

   struct lazy_enable_if_c<false, T> {};

   template <class Cond, class T> 

   struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {};

   template <bool B, class T = void>

   struct disable_if_c {

     typedef T type;

   };

   template <class T>

   struct disable_if_c<true, T> {};

   template <class Cond, class T = void> 

   struct disable_if : public disable_if_c<Cond::value, T> {};

   template <bool B, class T>

   struct lazy_disable_if_c {

     typedef typename T::type type;

   };

   template <class T>

   struct lazy_disable_if_c<true, T> {};

   template <class Cond, class T> 

   struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {};

 } // namespace lemon

 #endif