libstdc++
ext/functional
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1 // Functional extensions -*- C++ -*-
2 
3 // Copyright (C) 2002-2017 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
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 ext/functional
52  * This file is a GNU extension to the Standard C++ Library (possibly
53  * containing extensions from the HP/SGI STL subset).
54  */
55 
56 #ifndef _EXT_FUNCTIONAL
57 #define _EXT_FUNCTIONAL 1
58 
59 #pragma GCC system_header
60 
61 #include <functional>
62 
63 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
64 {
65 _GLIBCXX_BEGIN_NAMESPACE_VERSION
66 
67  using std::size_t;
68  using std::unary_function;
70  using std::mem_fun1_t;
72  using std::mem_fun1_ref_t;
74 
75  /** The @c identity_element functions are not part of the C++
76  * standard; SGI provided them as an extension. Its argument is an
77  * operation, and its return value is the identity element for that
78  * operation. It is overloaded for addition and multiplication,
79  * and you can overload it for your own nefarious operations.
80  *
81  * @addtogroup SGIextensions
82  * @{
83  */
84  /// An \link SGIextensions SGI extension \endlink.
85  template <class _Tp>
86  inline _Tp
87  identity_element(std::plus<_Tp>)
88  { return _Tp(0); }
89 
90  /// An \link SGIextensions SGI extension \endlink.
91  template <class _Tp>
92  inline _Tp
93  identity_element(std::multiplies<_Tp>)
94  { return _Tp(1); }
95  /** @} */
96 
97  /** As an extension to the binders, SGI provided composition functors and
98  * wrapper functions to aid in their creation. The @c unary_compose
99  * functor is constructed from two functions/functors, @c f and @c g.
100  * Calling @c operator() with a single argument @c x returns @c f(g(x)).
101  * The function @c compose1 takes the two functions and constructs a
102  * @c unary_compose variable for you.
103  *
104  * @c binary_compose is constructed from three functors, @c f, @c g1,
105  * and @c g2. Its @c operator() returns @c f(g1(x),g2(x)). The function
106  * compose2 takes f, g1, and g2, and constructs the @c binary_compose
107  * instance for you. For example, if @c f returns an int, then
108  * \code
109  * int answer = (compose2(f,g1,g2))(x);
110  * \endcode
111  * is equivalent to
112  * \code
113  * int temp1 = g1(x);
114  * int temp2 = g2(x);
115  * int answer = f(temp1,temp2);
116  * \endcode
117  * But the first form is more compact, and can be passed around as a
118  * functor to other algorithms.
119  *
120  * @addtogroup SGIextensions
121  * @{
122  */
123  /// An \link SGIextensions SGI extension \endlink.
124  template <class _Operation1, class _Operation2>
126  : public unary_function<typename _Operation2::argument_type,
127  typename _Operation1::result_type>
128  {
129  protected:
130  _Operation1 _M_fn1;
131  _Operation2 _M_fn2;
132 
133  public:
134  unary_compose(const _Operation1& __x, const _Operation2& __y)
135  : _M_fn1(__x), _M_fn2(__y) {}
136 
137  typename _Operation1::result_type
138  operator()(const typename _Operation2::argument_type& __x) const
139  { return _M_fn1(_M_fn2(__x)); }
140  };
141 
142  /// An \link SGIextensions SGI extension \endlink.
143  template <class _Operation1, class _Operation2>
145  compose1(const _Operation1& __fn1, const _Operation2& __fn2)
146  { return unary_compose<_Operation1,_Operation2>(__fn1, __fn2); }
147 
148  /// An \link SGIextensions SGI extension \endlink.
149  template <class _Operation1, class _Operation2, class _Operation3>
151  : public unary_function<typename _Operation2::argument_type,
152  typename _Operation1::result_type>
153  {
154  protected:
155  _Operation1 _M_fn1;
156  _Operation2 _M_fn2;
157  _Operation3 _M_fn3;
158 
159  public:
160  binary_compose(const _Operation1& __x, const _Operation2& __y,
161  const _Operation3& __z)
162  : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }
163 
164  typename _Operation1::result_type
165  operator()(const typename _Operation2::argument_type& __x) const
166  { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }
167  };
168 
169  /// An \link SGIextensions SGI extension \endlink.
170  template <class _Operation1, class _Operation2, class _Operation3>
172  compose2(const _Operation1& __fn1, const _Operation2& __fn2,
173  const _Operation3& __fn3)
175  (__fn1, __fn2, __fn3); }
176  /** @} */
177 
178  /** As an extension, SGI provided a functor called @c identity. When a
179  * functor is required but no operations are desired, this can be used as a
180  * pass-through. Its @c operator() returns its argument unchanged.
181  *
182  * @addtogroup SGIextensions
183  */
184  template <class _Tp>
185  struct identity
186  : public std::_Identity<_Tp> {};
187 
188  /** @c select1st and @c select2nd are extensions provided by SGI. Their
189  * @c operator()s
190  * take a @c std::pair as an argument, and return either the first member
191  * or the second member, respectively. They can be used (especially with
192  * the composition functors) to @a strip data from a sequence before
193  * performing the remainder of an algorithm.
194  *
195  * @addtogroup SGIextensions
196  * @{
197  */
198  /// An \link SGIextensions SGI extension \endlink.
199  template <class _Pair>
200  struct select1st
201  : public std::_Select1st<_Pair> {};
202 
203  /// An \link SGIextensions SGI extension \endlink.
204  template <class _Pair>
205  struct select2nd
206  : public std::_Select2nd<_Pair> {};
207 
208  /** @} */
209 
210  // extension documented next
211  template <class _Arg1, class _Arg2>
212  struct _Project1st : public binary_function<_Arg1, _Arg2, _Arg1>
213  {
214  _Arg1
215  operator()(const _Arg1& __x, const _Arg2&) const
216  { return __x; }
217  };
218 
219  template <class _Arg1, class _Arg2>
220  struct _Project2nd : public binary_function<_Arg1, _Arg2, _Arg2>
221  {
222  _Arg2
223  operator()(const _Arg1&, const _Arg2& __y) const
224  { return __y; }
225  };
226 
227  /** The @c operator() of the @c project1st functor takes two arbitrary
228  * arguments and returns the first one, while @c project2nd returns the
229  * second one. They are extensions provided by SGI.
230  *
231  * @addtogroup SGIextensions
232  * @{
233  */
234 
235  /// An \link SGIextensions SGI extension \endlink.
236  template <class _Arg1, class _Arg2>
237  struct project1st : public _Project1st<_Arg1, _Arg2> {};
238 
239  /// An \link SGIextensions SGI extension \endlink.
240  template <class _Arg1, class _Arg2>
241  struct project2nd : public _Project2nd<_Arg1, _Arg2> {};
242  /** @} */
243 
244  // extension documented next
245  template <class _Result>
246  struct _Constant_void_fun
247  {
248  typedef _Result result_type;
249  result_type _M_val;
250 
251  _Constant_void_fun(const result_type& __v) : _M_val(__v) {}
252 
253  const result_type&
254  operator()() const
255  { return _M_val; }
256  };
257 
258  template <class _Result, class _Argument>
259  struct _Constant_unary_fun
260  {
261  typedef _Argument argument_type;
262  typedef _Result result_type;
263  result_type _M_val;
264 
265  _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}
266 
267  const result_type&
268  operator()(const _Argument&) const
269  { return _M_val; }
270  };
271 
272  template <class _Result, class _Arg1, class _Arg2>
273  struct _Constant_binary_fun
274  {
275  typedef _Arg1 first_argument_type;
276  typedef _Arg2 second_argument_type;
277  typedef _Result result_type;
278  _Result _M_val;
279 
280  _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}
281 
282  const result_type&
283  operator()(const _Arg1&, const _Arg2&) const
284  { return _M_val; }
285  };
286 
287  /** These three functors are each constructed from a single arbitrary
288  * variable/value. Later, their @c operator()s completely ignore any
289  * arguments passed, and return the stored value.
290  * - @c constant_void_fun's @c operator() takes no arguments
291  * - @c constant_unary_fun's @c operator() takes one argument (ignored)
292  * - @c constant_binary_fun's @c operator() takes two arguments (ignored)
293  *
294  * The helper creator functions @c constant0, @c constant1, and
295  * @c constant2 each take a @a result argument and construct variables of
296  * the appropriate functor type.
297  *
298  * @addtogroup SGIextensions
299  * @{
300  */
301  /// An \link SGIextensions SGI extension \endlink.
302  template <class _Result>
304  : public _Constant_void_fun<_Result>
305  {
306  constant_void_fun(const _Result& __v)
307  : _Constant_void_fun<_Result>(__v) {}
308  };
309 
310  /// An \link SGIextensions SGI extension \endlink.
311  template <class _Result, class _Argument = _Result>
312  struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>
313  {
314  constant_unary_fun(const _Result& __v)
315  : _Constant_unary_fun<_Result, _Argument>(__v) {}
316  };
317 
318  /// An \link SGIextensions SGI extension \endlink.
319  template <class _Result, class _Arg1 = _Result, class _Arg2 = _Arg1>
321  : public _Constant_binary_fun<_Result, _Arg1, _Arg2>
322  {
323  constant_binary_fun(const _Result& __v)
324  : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}
325  };
326 
327  /// An \link SGIextensions SGI extension \endlink.
328  template <class _Result>
330  constant0(const _Result& __val)
331  { return constant_void_fun<_Result>(__val); }
332 
333  /// An \link SGIextensions SGI extension \endlink.
334  template <class _Result>
336  constant1(const _Result& __val)
337  { return constant_unary_fun<_Result, _Result>(__val); }
338 
339  /// An \link SGIextensions SGI extension \endlink.
340  template <class _Result>
342  constant2(const _Result& __val)
344  /** @} */
345 
346  /** The @c subtractive_rng class is documented on
347  * <a href="http://www.sgi.com/tech/stl/">SGI's site</a>.
348  * Note that this code assumes that @c int is 32 bits.
349  *
350  * @ingroup SGIextensions
351  */
353  : public unary_function<unsigned int, unsigned int>
354  {
355  private:
356  unsigned int _M_table[55];
357  size_t _M_index1;
358  size_t _M_index2;
359 
360  public:
361  /// Returns a number less than the argument.
362  unsigned int
363  operator()(unsigned int __limit)
364  {
365  _M_index1 = (_M_index1 + 1) % 55;
366  _M_index2 = (_M_index2 + 1) % 55;
367  _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];
368  return _M_table[_M_index1] % __limit;
369  }
370 
371  void
372  _M_initialize(unsigned int __seed)
373  {
374  unsigned int __k = 1;
375  _M_table[54] = __seed;
376  size_t __i;
377  for (__i = 0; __i < 54; __i++)
378  {
379  size_t __ii = (21 * (__i + 1) % 55) - 1;
380  _M_table[__ii] = __k;
381  __k = __seed - __k;
382  __seed = _M_table[__ii];
383  }
384  for (int __loop = 0; __loop < 4; __loop++)
385  {
386  for (__i = 0; __i < 55; __i++)
387  _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];
388  }
389  _M_index1 = 0;
390  _M_index2 = 31;
391  }
392 
393  /// Ctor allowing you to initialize the seed.
394  subtractive_rng(unsigned int __seed)
395  { _M_initialize(__seed); }
396 
397  /// Default ctor; initializes its state with some number you don't see.
399  { _M_initialize(161803398u); }
400  };
401 
402  // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,
403  // provided for backward compatibility, they are no longer part of
404  // the C++ standard.
405 
406  template <class _Ret, class _Tp, class _Arg>
408  mem_fun1(_Ret (_Tp::*__f)(_Arg))
409  { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
410 
411  template <class _Ret, class _Tp, class _Arg>
413  mem_fun1(_Ret (_Tp::*__f)(_Arg) const)
414  { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
415 
416  template <class _Ret, class _Tp, class _Arg>
418  mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))
419  { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
420 
421  template <class _Ret, class _Tp, class _Arg>
423  mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)
425 
426 _GLIBCXX_END_NAMESPACE_VERSION
427 } // namespace
428 
429 #endif
430 
An SGI extension .
Definition: ext/functional:200
An SGI extension .
Definition: ext/functional:125
One of the adaptors for member pointers.
An SGI extension .
Definition: ext/functional:237
An SGI extension .
Definition: ext/functional:205
_Arg argument_type
argument_type is the type of the argument
Definition: stl_function.h:108
One of the math functors.
Definition: stl_function.h:147
One of the adaptors for member pointers.
An SGI extension .
Definition: ext/functional:303
GNU extensions for public use.
constant_binary_fun< _Result, _Result, _Result > constant2(const _Result &__val)
An SGI extension .
Definition: ext/functional:342
binary_compose< _Operation1, _Operation2, _Operation3 > compose2(const _Operation1 &__fn1, const _Operation2 &__fn2, const _Operation3 &__fn3)
An SGI extension .
Definition: ext/functional:172
One of the math functors.
Definition: stl_function.h:153
One of the adaptors for member pointers.
unary_compose< _Operation1, _Operation2 > compose1(const _Operation1 &__fn1, const _Operation2 &__fn2)
An SGI extension .
Definition: ext/functional:145
unsigned int operator()(unsigned int __limit)
Returns a number less than the argument.
Definition: ext/functional:363
_Arg1 first_argument_type
first_argument_type is the type of the first argument
Definition: stl_function.h:121
An SGI extension .
Definition: ext/functional:241
subtractive_rng(unsigned int __seed)
Ctor allowing you to initialize the seed.
Definition: ext/functional:394
One of the adaptors for member pointers.
subtractive_rng()
Default ctor; initializes its state with some number you don&#39;t see.
Definition: ext/functional:398
_Result result_type
result_type is the return type
Definition: stl_function.h:111
constant_unary_fun< _Result, _Result > constant1(const _Result &__val)
An SGI extension .
Definition: ext/functional:336
constant_void_fun< _Result > constant0(const _Result &__val)
An SGI extension .
Definition: ext/functional:330
_Arg2 second_argument_type
second_argument_type is the type of the second argument
Definition: stl_function.h:124
An SGI extension .
Definition: ext/functional:150