lemon/bits/enable_if.h
author Alpar Juttner <alpar@cs.elte.hu>
Fri, 12 Dec 2008 21:52:53 +0000
branch1.0
changeset 350 d5cfcff85dfd
parent 220 a5d8c039f218
permissions -rw-r--r--
Merge bugfix #195
     1 /* -*- mode: C++; indent-tabs-mode: nil; -*-
     2  *
     3  * This file is a part of LEMON, a generic C++ optimization library.
     4  *
     5  * Copyright (C) 2003-2008
     6  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
     7  * (Egervary Research Group on Combinatorial Optimization, EGRES).
     8  *
     9  * Permission to use, modify and distribute this software is granted
    10  * provided that this copyright notice appears in all copies. For
    11  * precise terms see the accompanying LICENSE file.
    12  *
    13  * This software is provided "AS IS" with no warranty of any kind,
    14  * express or implied, and with no claim as to its suitability for any
    15  * purpose.
    16  *
    17  */
    18 
    19 // This file contains a modified version of the enable_if library from BOOST.
    20 // See the appropriate copyright notice below.
    21 
    22 // Boost enable_if library
    23 
    24 // Copyright 2003 (c) The Trustees of Indiana University.
    25 
    26 // Use, modification, and distribution is subject to the Boost Software
    27 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
    28 // http://www.boost.org/LICENSE_1_0.txt)
    29 
    30 //    Authors: Jaakko Jarvi (jajarvi at osl.iu.edu)
    31 //             Jeremiah Willcock (jewillco at osl.iu.edu)
    32 //             Andrew Lumsdaine (lums at osl.iu.edu)
    33 
    34 
    35 #ifndef LEMON_BITS_ENABLE_IF_H
    36 #define LEMON_BITS_ENABLE_IF_H
    37 
    38 //\file
    39 //\brief Miscellaneous basic utilities
    40 
    41 namespace lemon
    42 {
    43 
    44   // Basic type for defining "tags". A "YES" condition for \c enable_if.
    45 
    46   // Basic type for defining "tags". A "YES" condition for \c enable_if.
    47   //
    48   //\sa False
    49   struct True {
    50     //\e
    51     static const bool value = true;
    52   };
    53 
    54   // Basic type for defining "tags". A "NO" condition for \c enable_if.
    55 
    56   // Basic type for defining "tags". A "NO" condition for \c enable_if.
    57   //
    58   //\sa True
    59   struct False {
    60     //\e
    61     static const bool value = false;
    62   };
    63 
    64 
    65 
    66   template <typename T>
    67   struct Wrap {
    68     const T &value;
    69     Wrap(const T &t) : value(t) {}
    70   };
    71 
    72   /**************** dummy class to avoid ambiguity ****************/
    73 
    74   template<int T> struct dummy { dummy(int) {} };
    75 
    76   /**************** enable_if from BOOST ****************/
    77 
    78   template <typename Type, typename T = void>
    79   struct exists {
    80     typedef T type;
    81   };
    82 
    83 
    84   template <bool B, class T = void>
    85   struct enable_if_c {
    86     typedef T type;
    87   };
    88 
    89   template <class T>
    90   struct enable_if_c<false, T> {};
    91 
    92   template <class Cond, class T = void>
    93   struct enable_if : public enable_if_c<Cond::value, T> {};
    94 
    95   template <bool B, class T>
    96   struct lazy_enable_if_c {
    97     typedef typename T::type type;
    98   };
    99 
   100   template <class T>
   101   struct lazy_enable_if_c<false, T> {};
   102 
   103   template <class Cond, class T>
   104   struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {};
   105 
   106 
   107   template <bool B, class T = void>
   108   struct disable_if_c {
   109     typedef T type;
   110   };
   111 
   112   template <class T>
   113   struct disable_if_c<true, T> {};
   114 
   115   template <class Cond, class T = void>
   116   struct disable_if : public disable_if_c<Cond::value, T> {};
   117 
   118   template <bool B, class T>
   119   struct lazy_disable_if_c {
   120     typedef typename T::type type;
   121   };
   122 
   123   template <class T>
   124   struct lazy_disable_if_c<true, T> {};
   125 
   126   template <class Cond, class T>
   127   struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {};
   128 
   129 } // namespace lemon
   130 
   131 #endif