/* -*- C++ -*-

  *

  * src/lemon/utility.h - Part of LEMON, a generic C++ optimization library

  *

  * Copyright (C) 2005 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_UTILITY_H

 #define LEMON_UTILITY_H

 namespace lemon

 {

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

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

   /// file.

   struct True {

     static const bool value = true;

   };

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

   struct False {

     static const bool value = false;

   };

   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