1 // Functor implementations -*- C++ -*-
2
3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009, 2010, 2011
4 // Free Software Foundation, Inc.
5 //
6 // This file is part of the GNU ISO C++ Library. This library is free
7 // software; you can redistribute it and/or modify it under the
8 // terms of the GNU General Public License as published by the
9 // Free Software Foundation; either version 3, or (at your option)
10 // any later version.
11
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
20
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 // <http://www.gnu.org/licenses/>.
25
26 /*
27 *
28 * Copyright (c) 1994
29 * Hewlett-Packard Company
30 *
31 * Permission to use, copy, modify, distribute and sell this software
32 * and its documentation for any purpose is hereby granted without fee,
33 * provided that the above copyright notice appear in all copies and
34 * that both that copyright notice and this permission notice appear
35 * in supporting documentation. Hewlett-Packard Company makes no
36 * representations about the suitability of this software for any
37 * purpose. It is provided "as is" without express or implied warranty.
38 *
39 *
40 * Copyright (c) 1996-1998
41 * Silicon Graphics Computer Systems, Inc.
42 *
43 * Permission to use, copy, modify, distribute and sell this software
44 * and its documentation for any purpose is hereby granted without fee,
45 * provided that the above copyright notice appear in all copies and
46 * that both that copyright notice and this permission notice appear
47 * in supporting documentation. Silicon Graphics makes no
48 * representations about the suitability of this software for any
49 * purpose. It is provided "as is" without express or implied warranty.
50 */
51
52 /** @file backward/binders.h
53 * This is an internal header file, included by other library headers.
54 * Do not attempt to use it directly. @headername{functional}
55 */
56
57 #ifndef _BACKWARD_BINDERS_H
58 #define _BACKWARD_BINDERS_H 1
59
_GLIBCXX_VISIBILITY(default)60 namespace std _GLIBCXX_VISIBILITY(default)
61 {
62 _GLIBCXX_BEGIN_NAMESPACE_VERSION
63
64 // 20.3.6 binders
65 /** @defgroup binders Binder Classes
66 * @ingroup functors
67 *
68 * Binders turn functions/functors with two arguments into functors
69 * with a single argument, storing an argument to be applied later.
70 * For example, a variable @c B of type @c binder1st is constructed
71 * from a functor @c f and an argument @c x. Later, B's @c
72 * operator() is called with a single argument @c y. The return
73 * value is the value of @c f(x,y). @c B can be @a called with
74 * various arguments (y1, y2, ...) and will in turn call @c
75 * f(x,y1), @c f(x,y2), ...
76 *
77 * The function @c bind1st is provided to save some typing. It takes the
78 * function and an argument as parameters, and returns an instance of
79 * @c binder1st.
80 *
81 * The type @c binder2nd and its creator function @c bind2nd do the same
82 * thing, but the stored argument is passed as the second parameter instead
83 * of the first, e.g., @c bind2nd(std::minus<float>(),1.3) will create a
84 * functor whose @c operator() accepts a floating-point number, subtracts
85 * 1.3 from it, and returns the result. (If @c bind1st had been used,
86 * the functor would perform <em>1.3 - x</em> instead.
87 *
88 * Creator-wrapper functions like @c bind1st are intended to be used in
89 * calling algorithms. Their return values will be temporary objects.
90 * (The goal is to not require you to type names like
91 * @c std::binder1st<std::plus<int>> for declaring a variable to hold the
92 * return value from @c bind1st(std::plus<int>(),5).
93 *
94 * These become more useful when combined with the composition functions.
95 *
96 * These functions are deprecated in C++11 and can be replaced by
97 * @c std::bind (or @c std::tr1::bind) which is more powerful and flexible,
98 * supporting functions with any number of arguments. Uses of @c bind1st
99 * can be replaced by @c std::bind(f, x, std::placeholders::_1) and
100 * @c bind2nd by @c std::bind(f, std::placeholders::_1, x).
101 * @{
102 */
103 /// One of the @link binders binder functors@endlink.
104 template<typename _Operation>
105 class binder1st
106 : public unary_function<typename _Operation::second_argument_type,
107 typename _Operation::result_type>
108 {
109 protected:
110 _Operation op;
111 typename _Operation::first_argument_type value;
112
113 public:
114 binder1st(const _Operation& __x,
115 const typename _Operation::first_argument_type& __y)
116 : op(__x), value(__y) { }
117
118 typename _Operation::result_type
119 operator()(const typename _Operation::second_argument_type& __x) const
120 { return op(value, __x); }
121
122 // _GLIBCXX_RESOLVE_LIB_DEFECTS
123 // 109. Missing binders for non-const sequence elements
124 typename _Operation::result_type
125 operator()(typename _Operation::second_argument_type& __x) const
126 { return op(value, __x); }
127 } _GLIBCXX_DEPRECATED;
128
129 /// One of the @link binders binder functors@endlink.
130 template<typename _Operation, typename _Tp>
131 inline binder1st<_Operation>
132 bind1st(const _Operation& __fn, const _Tp& __x)
133 {
134 typedef typename _Operation::first_argument_type _Arg1_type;
135 return binder1st<_Operation>(__fn, _Arg1_type(__x));
136 }
137
138 /// One of the @link binders binder functors@endlink.
139 template<typename _Operation>
140 class binder2nd
141 : public unary_function<typename _Operation::first_argument_type,
142 typename _Operation::result_type>
143 {
144 protected:
145 _Operation op;
146 typename _Operation::second_argument_type value;
147
148 public:
149 binder2nd(const _Operation& __x,
150 const typename _Operation::second_argument_type& __y)
151 : op(__x), value(__y) { }
152
153 typename _Operation::result_type
154 operator()(const typename _Operation::first_argument_type& __x) const
155 { return op(__x, value); }
156
157 // _GLIBCXX_RESOLVE_LIB_DEFECTS
158 // 109. Missing binders for non-const sequence elements
159 typename _Operation::result_type
160 operator()(typename _Operation::first_argument_type& __x) const
161 { return op(__x, value); }
162 } _GLIBCXX_DEPRECATED;
163
164 /// One of the @link binders binder functors@endlink.
165 template<typename _Operation, typename _Tp>
166 inline binder2nd<_Operation>
167 bind2nd(const _Operation& __fn, const _Tp& __x)
168 {
169 typedef typename _Operation::second_argument_type _Arg2_type;
170 return binder2nd<_Operation>(__fn, _Arg2_type(__x));
171 }
172 /** @} */
173
174 _GLIBCXX_END_NAMESPACE_VERSION
175 } // namespace
176
177 #endif /* _BACKWARD_BINDERS_H */
178