1 // Functor implementations -*- C++ -*-
2
3 // Copyright (C) 2001-2023 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
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU 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 /*
26 *
27 * Copyright (c) 1994
28 * Hewlett-Packard Company
29 *
30 * Permission to use, copy, modify, distribute and sell this software
31 * and its documentation for any purpose is hereby granted without fee,
32 * provided that the above copyright notice appear in all copies and
33 * that both that copyright notice and this permission notice appear
34 * in supporting documentation. Hewlett-Packard Company makes no
35 * representations about the suitability of this software for any
36 * purpose. It is provided "as is" without express or implied warranty.
37 *
38 *
39 * Copyright (c) 1996-1998
40 * Silicon Graphics Computer Systems, Inc.
41 *
42 * Permission to use, copy, modify, distribute and sell this software
43 * and its documentation for any purpose is hereby granted without fee,
44 * provided that the above copyright notice appear in all copies and
45 * that both that copyright notice and this permission notice appear
46 * in supporting documentation. Silicon Graphics makes no
47 * representations about the suitability of this software for any
48 * purpose. It is provided "as is" without express or implied warranty.
49 */
50
51 /** @file backward/binders.h
52 * This is an internal header file, included by other library headers.
53 * Do not attempt to use it directly. @headername{functional}
54 */
55
56 #ifndef _BACKWARD_BINDERS_H
57 #define _BACKWARD_BINDERS_H 1
58
59 // Suppress deprecated warning for this file.
60 #pragma GCC diagnostic push
61 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
62
63 namespace std _GLIBCXX_VISIBILITY(default)
64 {
65 _GLIBCXX_BEGIN_NAMESPACE_VERSION
66
67 // 20.3.6 binders
68 /** @defgroup binders Binder Classes
69 * @ingroup functors
70 *
71 * Binders turn functions/functors with two arguments into functors
72 * with a single argument, storing an argument to be applied later.
73 * For example, a variable @c B of type @c binder1st is constructed
74 * from a functor @c f and an argument @c x. Later, B's @c
75 * operator() is called with a single argument @c y. The return
76 * value is the value of @c f(x,y). @c B can be @a called with
77 * various arguments (y1, y2, ...) and will in turn call @c
78 * f(x,y1), @c f(x,y2), ...
79 *
80 * The function @c bind1st is provided to save some typing. It takes the
81 * function and an argument as parameters, and returns an instance of
82 * @c binder1st.
83 *
84 * The type @c binder2nd and its creator function @c bind2nd do the same
85 * thing, but the stored argument is passed as the second parameter instead
86 * of the first, e.g., @c bind2nd(std::minus<float>(),1.3) will create a
87 * functor whose @c operator() accepts a floating-point number, subtracts
88 * 1.3 from it, and returns the result. (If @c bind1st had been used,
89 * the functor would perform <em>1.3 - x</em> instead.
90 *
91 * Creator-wrapper functions like @c bind1st are intended to be used in
92 * calling algorithms. Their return values will be temporary objects.
93 * (The goal is to not require you to type names like
94 * @c std::binder1st<std::plus<int>> for declaring a variable to hold the
95 * return value from @c bind1st(std::plus<int>(),5).
96 *
97 * These become more useful when combined with the composition functions.
98 *
99 * These functions are deprecated in C++11 and can be replaced by
100 * @c std::bind (or @c std::tr1::bind) which is more powerful and flexible,
101 * supporting functions with any number of arguments. Uses of @c bind1st
102 * can be replaced by @c std::bind(f, x, std::placeholders::_1) and
103 * @c bind2nd by @c std::bind(f, std::placeholders::_1, x).
104 * @{
105 */
106 /// One of the @link binders binder functors@endlink.
107 template<typename _Operation>
108 class binder1st
109 : public unary_function<typename _Operation::second_argument_type,
110 typename _Operation::result_type>
111 {
112 protected:
113 _Operation op;
114 typename _Operation::first_argument_type value;
115
116 public:
117 binder1st(const _Operation& __x,
118 const typename _Operation::first_argument_type& __y)
119 : op(__x), value(__y) { }
120
121 typename _Operation::result_type
122 operator()(const typename _Operation::second_argument_type& __x) const
123 { return op(value, __x); }
124
125 // _GLIBCXX_RESOLVE_LIB_DEFECTS
126 // 109. Missing binders for non-const sequence elements
127 typename _Operation::result_type
128 operator()(typename _Operation::second_argument_type& __x) const
129 { return op(value, __x); }
130 } _GLIBCXX11_DEPRECATED_SUGGEST("std::bind");
131
132 /// One of the @link binders binder functors@endlink.
133 template<typename _Operation, typename _Tp>
134 _GLIBCXX11_DEPRECATED_SUGGEST("std::bind")
135 inline binder1st<_Operation>
136 bind1st(const _Operation& __fn, const _Tp& __x)
137 {
138 typedef typename _Operation::first_argument_type _Arg1_type;
139 return binder1st<_Operation>(__fn, _Arg1_type(__x));
140 }
141
142 /// One of the @link binders binder functors@endlink.
143 template<typename _Operation>
144 class binder2nd
145 : public unary_function<typename _Operation::first_argument_type,
146 typename _Operation::result_type>
147 {
148 protected:
149 _Operation op;
150 typename _Operation::second_argument_type value;
151
152 public:
153 binder2nd(const _Operation& __x,
154 const typename _Operation::second_argument_type& __y)
155 : op(__x), value(__y) { }
156
157 typename _Operation::result_type
158 operator()(const typename _Operation::first_argument_type& __x) const
159 { return op(__x, value); }
160
161 // _GLIBCXX_RESOLVE_LIB_DEFECTS
162 // 109. Missing binders for non-const sequence elements
163 typename _Operation::result_type
164 operator()(typename _Operation::first_argument_type& __x) const
165 { return op(__x, value); }
166 } _GLIBCXX11_DEPRECATED_SUGGEST("std::bind");
167
168 /// One of the @link binders binder functors@endlink.
169 template<typename _Operation, typename _Tp>
170 _GLIBCXX11_DEPRECATED_SUGGEST("std::bind")
171 inline binder2nd<_Operation>
172 bind2nd(const _Operation& __fn, const _Tp& __x)
173 {
174 typedef typename _Operation::second_argument_type _Arg2_type;
175 return binder2nd<_Operation>(__fn, _Arg2_type(__x));
176 }
177 /** @} */
178
179 _GLIBCXX_END_NAMESPACE_VERSION
180 } // namespace
181
182 #pragma GCC diagnostic pop
183
184 #endif /* _BACKWARD_BINDERS_H */