1// -*- C++ -*-
2
3// Copyright (C) 2005-2015 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>
48#include <ext/pb_ds/detail/types_traits.hpp>
49
50namespace __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
70