/* -*- C++ -*-

 *

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

 *

 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi

 * Kutatocsoport (Egervary Combinatorial Optimization Research Group,

 * 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