libstdc++
eq_by_less.hpp
Go to the documentation of this file.
1 // -*- C++ -*-
2 
3 // Copyright (C) 2005, 2006, 2009, 2011 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the terms
7 // of the GNU General Public License as published by the Free Software
8 // Foundation; either version 3, or (at your option) any later
9 // version.
10 
11 // This library is distributed in the hope that it will be useful, but
12 // WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 // General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 // Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
26 
27 // Permission to use, copy, modify, sell, and distribute this software
28 // is hereby granted without fee, provided that the above copyright
29 // notice appears in all copies, and that both that copyright notice
30 // and this permission notice appear in supporting documentation. None
31 // of the above authors, nor IBM Haifa Research Laboratories, make any
32 // representation about the suitability of this software for any
33 // purpose. It is provided "as is" without express or implied
34 // warranty.
35 
36 /**
37  * @file eq_by_less.hpp
38  * Contains an equivalence function.
39  */
40 
41 #ifndef PB_DS_EQ_BY_LESS_HPP
42 #define PB_DS_EQ_BY_LESS_HPP
43 
44 #include <utility>
45 #include <functional>
46 #include <vector>
47 #include <assert.h>
49 
50 namespace __gnu_pbds
51 {
52  namespace detail
53  {
54  /// Equivalence function.
55  template<typename Key, class Cmp_Fn>
56  struct eq_by_less : private Cmp_Fn
57  {
58  bool
59  operator()(const Key& r_lhs, const Key& r_rhs) const
60  {
61  const bool l = Cmp_Fn::operator()(r_lhs, r_rhs);
62  const bool g = Cmp_Fn::operator()(r_rhs, r_lhs);
63  return !(l || g);
64  }
65  };
66  } // namespace detail
67 } // namespace __gnu_pbds
68 
69 #endif // #ifndef PB_DS_EQ_BY_LESS_HPP
Equivalence function.
Definition: eq_by_less.hpp:56