1 /* -*- C++ -*-
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 � 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 J�rvi (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;
WrapWrap78     Wrap(const T &t) : value(t) {}
79   };
80 
81   /**************** dummy class to avoid ambiguity ****************/
82 
dummydummy83   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
141