alpar@7: /* -*- C++ -*-
alpar@7:  *
alpar@7:  * This file is a part of LEMON, a generic C++ optimization library
alpar@7:  *
alpar@7:  * Copyright (C) 2003-2007
alpar@7:  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
alpar@7:  * (Egervary Research Group on Combinatorial Optimization, EGRES).
alpar@7:  *
alpar@7:  * Permission to use, modify and distribute this software is granted
alpar@7:  * provided that this copyright notice appears in all copies. For
alpar@7:  * precise terms see the accompanying LICENSE file.
alpar@7:  *
alpar@7:  * This software is provided "AS IS" with no warranty of any kind,
alpar@7:  * express or implied, and with no claim as to its suitability for any
alpar@7:  * purpose.
alpar@7:  *
alpar@7:  */
alpar@7: 
alpar@7: // This file contains a modified version of the enable_if library from BOOST.
alpar@7: // See the appropriate copyright notice below.
alpar@7: 
alpar@7: // Boost enable_if library
alpar@7: 
alpar@7: // Copyright 2003 © The Trustees of Indiana University.
alpar@7: 
alpar@7: // Use, modification, and distribution is subject to the Boost Software
alpar@7: // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
alpar@7: // http://www.boost.org/LICENSE_1_0.txt)
alpar@7: 
alpar@7: //    Authors: Jaakko Järvi (jajarvi at osl.iu.edu)
alpar@7: //             Jeremiah Willcock (jewillco at osl.iu.edu)
alpar@7: //             Andrew Lumsdaine (lums at osl.iu.edu)
alpar@7: 
alpar@7: 
alpar@7: #ifndef LEMON_BITS_UTILITY_H
alpar@7: #define LEMON_BITS_UTILITY_H
alpar@7: 
alpar@7: ///\file
alpar@7: ///\brief Miscellaneous basic utilities
alpar@7: ///
alpar@7: ///\todo Please rethink the organisation of the basic files like this.
alpar@7: ///E.g. this file might be merged with invalid.h.
alpar@7: 
alpar@7: 
alpar@7: namespace lemon
alpar@7: {
alpar@7: 
alpar@7:   /// Basic type for defining "tags". A "YES" condition for \c enable_if.
alpar@7: 
alpar@7:   /// Basic type for defining "tags". A "YES" condition for \c enable_if.
alpar@7:   ///
alpar@7:   ///\sa False
alpar@7:   ///
alpar@7:   /// \todo This should go to a separate "basic_types.h" (or something)
alpar@7:   /// file.
alpar@7:   struct True {
alpar@7:     ///\e
alpar@7:     static const bool value = true;
alpar@7:   };
alpar@7: 
alpar@7:   /// Basic type for defining "tags". A "NO" condition for \c enable_if.
alpar@7: 
alpar@7:   /// Basic type for defining "tags". A "NO" condition for \c enable_if.
alpar@7:   ///
alpar@7:   ///\sa True
alpar@7:   struct False {
alpar@7:     ///\e
alpar@7:     static const bool value = false;
alpar@7:   };
alpar@7: 
alpar@7: 
alpar@7:   struct InvalidType {
alpar@7:   };
alpar@7: 
alpar@7:   template <typename T>
alpar@7:   struct Wrap {
alpar@7:     const T &value;
alpar@7:     Wrap(const T &t) : value(t) {}
alpar@7:   };
alpar@7: 
alpar@7:   /**************** dummy class to avoid ambiguity ****************/
alpar@7: 
alpar@7:   template<int T> struct dummy { dummy(int) {} };
alpar@7: 
alpar@7:   /**************** enable_if from BOOST ****************/
alpar@7:   
alpar@7:   template <typename Type, typename T = void>
alpar@7:   struct exists {
alpar@7:     typedef T type;
alpar@7:   };
alpar@7: 
alpar@7:  
alpar@7:   template <bool B, class T = void>
alpar@7:   struct enable_if_c {
alpar@7:     typedef T type;
alpar@7:   };
alpar@7: 
alpar@7:   template <class T>
alpar@7:   struct enable_if_c<false, T> {};
alpar@7: 
alpar@7:   template <class Cond, class T = void> 
alpar@7:   struct enable_if : public enable_if_c<Cond::value, T> {};
alpar@7: 
alpar@7:   template <bool B, class T>
alpar@7:   struct lazy_enable_if_c {
alpar@7:     typedef typename T::type type;
alpar@7:   };
alpar@7: 
alpar@7:   template <class T>
alpar@7:   struct lazy_enable_if_c<false, T> {};
alpar@7: 
alpar@7:   template <class Cond, class T> 
alpar@7:   struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {};
alpar@7: 
alpar@7: 
alpar@7:   template <bool B, class T = void>
alpar@7:   struct disable_if_c {
alpar@7:     typedef T type;
alpar@7:   };
alpar@7: 
alpar@7:   template <class T>
alpar@7:   struct disable_if_c<true, T> {};
alpar@7: 
alpar@7:   template <class Cond, class T = void> 
alpar@7:   struct disable_if : public disable_if_c<Cond::value, T> {};
alpar@7: 
alpar@7:   template <bool B, class T>
alpar@7:   struct lazy_disable_if_c {
alpar@7:     typedef typename T::type type;
alpar@7:   };
alpar@7: 
alpar@7:   template <class T>
alpar@7:   struct lazy_disable_if_c<true, T> {};
alpar@7: 
alpar@7:   template <class Cond, class T> 
alpar@7:   struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {};
alpar@7: 
alpar@7: } // namespace lemon
alpar@7: 
alpar@7: #endif