lemon/bits/utility.h
author Peter Kovacs <kpeter@inf.elte.hu>
Fri, 04 Jan 2008 03:29:54 +0100
changeset 28 e337bdf46777
child 39 0a01d811071f
permissions -rw-r--r--
Doc improvements.
     1 /* -*- C++ -*-
     2  *
     3  * This file is a part of LEMON, a generic C++ optimization library
     4  *
     5  * Copyright (C) 2003-2007
     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 © 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 Järvi (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_UTILITY_H
    36 #define LEMON_BITS_UTILITY_H
    37 
    38 ///\file
    39 ///\brief Miscellaneous basic utilities
    40 ///
    41 ///\todo Please rethink the organisation of the basic files like this.
    42 ///E.g. this file might be merged with invalid.h.
    43 
    44 
    45 namespace lemon
    46 {
    47 
    48   /// Basic type for defining "tags". A "YES" condition for \c enable_if.
    49 
    50   /// Basic type for defining "tags". A "YES" condition for \c enable_if.
    51   ///
    52   ///\sa False
    53   ///
    54   /// \todo This should go to a separate "basic_types.h" (or something)
    55   /// file.
    56   struct True {
    57     ///\e
    58     static const bool value = true;
    59   };
    60 
    61   /// Basic type for defining "tags". A "NO" condition for \c enable_if.
    62 
    63   /// Basic type for defining "tags". A "NO" condition for \c enable_if.
    64   ///
    65   ///\sa True
    66   struct False {
    67     ///\e
    68     static const bool value = false;
    69   };
    70 
    71 
    72   struct InvalidType {
    73   };
    74 
    75   template <typename T>
    76   struct Wrap {
    77     const T &value;
    78     Wrap(const T &t) : value(t) {}
    79   };
    80 
    81   /**************** dummy class to avoid ambiguity ****************/
    82 
    83   template<int T> struct dummy { dummy(int) {} };
    84 
    85   /**************** enable_if from BOOST ****************/
    86   
    87   template <typename Type, typename T = void>
    88   struct exists {
    89     typedef T type;
    90   };
    91 
    92  
    93   template <bool B, class T = void>
    94   struct enable_if_c {
    95     typedef T type;
    96   };
    97 
    98   template <class T>
    99   struct enable_if_c<false, T> {};
   100 
   101   template <class Cond, class T = void> 
   102   struct enable_if : public enable_if_c<Cond::value, T> {};
   103 
   104   template <bool B, class T>
   105   struct lazy_enable_if_c {
   106     typedef typename T::type type;
   107   };
   108 
   109   template <class T>
   110   struct lazy_enable_if_c<false, T> {};
   111 
   112   template <class Cond, class T> 
   113   struct lazy_enable_if : public lazy_enable_if_c<Cond::value, T> {};
   114 
   115 
   116   template <bool B, class T = void>
   117   struct disable_if_c {
   118     typedef T type;
   119   };
   120 
   121   template <class T>
   122   struct disable_if_c<true, T> {};
   123 
   124   template <class Cond, class T = void> 
   125   struct disable_if : public disable_if_c<Cond::value, T> {};
   126 
   127   template <bool B, class T>
   128   struct lazy_disable_if_c {
   129     typedef typename T::type type;
   130   };
   131 
   132   template <class T>
   133   struct lazy_disable_if_c<true, T> {};
   134 
   135   template <class Cond, class T> 
   136   struct lazy_disable_if : public lazy_disable_if_c<Cond::value, T> {};
   137 
   138 } // namespace lemon
   139 
   140 #endif