1 // Functional extensions -*- C++ -*-
3 // Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2009
4 // Free Software Foundation, Inc.
6 // This file is part of the GNU ISO C++ Library. This library is free
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8 // terms of the GNU General Public License as published by the
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18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
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29 * Hewlett-Packard Company
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.
41 * Silicon Graphics Computer Systems, Inc.
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.
52 /** @file ext/functional
53 * This file is a GNU extension to the Standard C++ Library (possibly
54 * containing extensions from the HP/SGI STL subset).
57 #ifndef _EXT_FUNCTIONAL
58 #define _EXT_FUNCTIONAL 1
60 #pragma GCC system_header
65 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
68 using std::unary_function;
69 using std::binary_function;
70 using std::mem_fun1_t;
71 using std::const_mem_fun1_t;
72 using std::mem_fun1_ref_t;
73 using std::const_mem_fun1_ref_t;
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.
81 * @addtogroup SGIextensions
84 /// An \link SGIextensions SGI extension \endlink.
87 identity_element(std::plus<_Tp>)
90 /// An \link SGIextensions SGI extension \endlink.
93 identity_element(std::multiplies<_Tp>)
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.
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
109 * int answer = (compose2(f,g1,g2))(x);
115 * int answer = f(temp1,temp2);
117 * But the first form is more compact, and can be passed around as a
118 * functor to other algorithms.
120 * @addtogroup SGIextensions
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>
134 unary_compose(const _Operation1& __x, const _Operation2& __y)
135 : _M_fn1(__x), _M_fn2(__y) {}
137 typename _Operation1::result_type
138 operator()(const typename _Operation2::argument_type& __x) const
139 { return _M_fn1(_M_fn2(__x)); }
142 /// An \link SGIextensions SGI extension \endlink.
143 template <class _Operation1, class _Operation2>
144 inline unary_compose<_Operation1, _Operation2>
145 compose1(const _Operation1& __fn1, const _Operation2& __fn2)
146 { return unary_compose<_Operation1,_Operation2>(__fn1, __fn2); }
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>
160 binary_compose(const _Operation1& __x, const _Operation2& __y,
161 const _Operation3& __z)
162 : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }
164 typename _Operation1::result_type
165 operator()(const typename _Operation2::argument_type& __x) const
166 { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }
169 /// An \link SGIextensions SGI extension \endlink.
170 template <class _Operation1, class _Operation2, class _Operation3>
171 inline binary_compose<_Operation1, _Operation2, _Operation3>
172 compose2(const _Operation1& __fn1, const _Operation2& __fn2,
173 const _Operation3& __fn3)
174 { return binary_compose<_Operation1, _Operation2, _Operation3>
175 (__fn1, __fn2, __fn3); }
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.
182 * @addtogroup SGIextensions
185 struct identity : public std::_Identity<_Tp> {};
187 /** @c select1st and @c select2nd are extensions provided by SGI. Their
189 * take a @c std::pair as an argument, and return either the first member
190 * or the second member, respectively. They can be used (especially with
191 * the composition functors) to "strip" data from a sequence before
192 * performing the remainder of an algorithm.
194 * @addtogroup SGIextensions
197 /// An \link SGIextensions SGI extension \endlink.
198 template <class _Pair>
199 struct select1st : public std::_Select1st<_Pair> {};
201 /// An \link SGIextensions SGI extension \endlink.
202 template <class _Pair>
203 struct select2nd : public std::_Select2nd<_Pair> {};
206 // extension documented next
207 template <class _Arg1, class _Arg2>
208 struct _Project1st : public binary_function<_Arg1, _Arg2, _Arg1>
211 operator()(const _Arg1& __x, const _Arg2&) const
215 template <class _Arg1, class _Arg2>
216 struct _Project2nd : public binary_function<_Arg1, _Arg2, _Arg2>
219 operator()(const _Arg1&, const _Arg2& __y) const
223 /** The @c operator() of the @c project1st functor takes two arbitrary
224 * arguments and returns the first one, while @c project2nd returns the
225 * second one. They are extensions provided by SGI.
227 * @addtogroup SGIextensions
231 /// An \link SGIextensions SGI extension \endlink.
232 template <class _Arg1, class _Arg2>
233 struct project1st : public _Project1st<_Arg1, _Arg2> {};
235 /// An \link SGIextensions SGI extension \endlink.
236 template <class _Arg1, class _Arg2>
237 struct project2nd : public _Project2nd<_Arg1, _Arg2> {};
240 // extension documented next
241 template <class _Result>
242 struct _Constant_void_fun
244 typedef _Result result_type;
247 _Constant_void_fun(const result_type& __v) : _M_val(__v) {}
254 template <class _Result, class _Argument>
255 struct _Constant_unary_fun
257 typedef _Argument argument_type;
258 typedef _Result result_type;
261 _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}
264 operator()(const _Argument&) const
268 template <class _Result, class _Arg1, class _Arg2>
269 struct _Constant_binary_fun
271 typedef _Arg1 first_argument_type;
272 typedef _Arg2 second_argument_type;
273 typedef _Result result_type;
276 _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}
279 operator()(const _Arg1&, const _Arg2&) const
283 /** These three functors are each constructed from a single arbitrary
284 * variable/value. Later, their @c operator()s completely ignore any
285 * arguments passed, and return the stored value.
286 * - @c constant_void_fun's @c operator() takes no arguments
287 * - @c constant_unary_fun's @c operator() takes one argument (ignored)
288 * - @c constant_binary_fun's @c operator() takes two arguments (ignored)
290 * The helper creator functions @c constant0, @c constant1, and
291 * @c constant2 each take a "result" argument and construct variables of
292 * the appropriate functor type.
294 * @addtogroup SGIextensions
297 /// An \link SGIextensions SGI extension \endlink.
298 template <class _Result>
299 struct constant_void_fun
300 : public _Constant_void_fun<_Result>
302 constant_void_fun(const _Result& __v)
303 : _Constant_void_fun<_Result>(__v) {}
306 /// An \link SGIextensions SGI extension \endlink.
307 template <class _Result, class _Argument = _Result>
308 struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>
310 constant_unary_fun(const _Result& __v)
311 : _Constant_unary_fun<_Result, _Argument>(__v) {}
314 /// An \link SGIextensions SGI extension \endlink.
315 template <class _Result, class _Arg1 = _Result, class _Arg2 = _Arg1>
316 struct constant_binary_fun
317 : public _Constant_binary_fun<_Result, _Arg1, _Arg2>
319 constant_binary_fun(const _Result& __v)
320 : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}
323 /// An \link SGIextensions SGI extension \endlink.
324 template <class _Result>
325 inline constant_void_fun<_Result>
326 constant0(const _Result& __val)
327 { return constant_void_fun<_Result>(__val); }
329 /// An \link SGIextensions SGI extension \endlink.
330 template <class _Result>
331 inline constant_unary_fun<_Result, _Result>
332 constant1(const _Result& __val)
333 { return constant_unary_fun<_Result, _Result>(__val); }
335 /// An \link SGIextensions SGI extension \endlink.
336 template <class _Result>
337 inline constant_binary_fun<_Result,_Result,_Result>
338 constant2(const _Result& __val)
339 { return constant_binary_fun<_Result, _Result, _Result>(__val); }
342 /** The @c subtractive_rng class is documented on
343 * <a href="http://www.sgi.com/tech/stl/">SGI's site</a>.
344 * Note that this code assumes that @c int is 32 bits.
346 * @ingroup SGIextensions
348 class subtractive_rng
349 : public unary_function<unsigned int, unsigned int>
352 unsigned int _M_table[55];
357 /// Returns a number less than the argument.
359 operator()(unsigned int __limit)
361 _M_index1 = (_M_index1 + 1) % 55;
362 _M_index2 = (_M_index2 + 1) % 55;
363 _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];
364 return _M_table[_M_index1] % __limit;
368 _M_initialize(unsigned int __seed)
370 unsigned int __k = 1;
371 _M_table[54] = __seed;
373 for (__i = 0; __i < 54; __i++)
375 size_t __ii = (21 * (__i + 1) % 55) - 1;
376 _M_table[__ii] = __k;
378 __seed = _M_table[__ii];
380 for (int __loop = 0; __loop < 4; __loop++)
382 for (__i = 0; __i < 55; __i++)
383 _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];
389 /// Ctor allowing you to initialize the seed.
390 subtractive_rng(unsigned int __seed)
391 { _M_initialize(__seed); }
393 /// Default ctor; initializes its state with some number you don't see.
395 { _M_initialize(161803398u); }
398 // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,
399 // provided for backward compatibility, they are no longer part of
402 template <class _Ret, class _Tp, class _Arg>
403 inline mem_fun1_t<_Ret, _Tp, _Arg>
404 mem_fun1(_Ret (_Tp::*__f)(_Arg))
405 { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
407 template <class _Ret, class _Tp, class _Arg>
408 inline const_mem_fun1_t<_Ret, _Tp, _Arg>
409 mem_fun1(_Ret (_Tp::*__f)(_Arg) const)
410 { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
412 template <class _Ret, class _Tp, class _Arg>
413 inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
414 mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))
415 { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
417 template <class _Ret, class _Tp, class _Arg>
418 inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
419 mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)
420 { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
422 _GLIBCXX_END_NAMESPACE