1 // Functor implementations -*- C++ -*-
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51 /** @file bits/stl_function.h
52 * This is an internal header file, included by other library headers.
53 * Do not attempt to use it directly. @headername{functional}
56 #ifndef _STL_FUNCTION_H
57 #define _STL_FUNCTION_H 1
59 namespace std _GLIBCXX_VISIBILITY(default)
61 _GLIBCXX_BEGIN_NAMESPACE_VERSION
63 // 20.3.1 base classes
64 /** @defgroup functors Function Objects
67 * Function objects, or @e functors, are objects with an @c operator()
68 * defined and accessible. They can be passed as arguments to algorithm
69 * templates and used in place of a function pointer. Not only is the
70 * resulting expressiveness of the library increased, but the generated
71 * code can be more efficient than what you might write by hand. When we
72 * refer to @a functors, then, generally we include function pointers in
73 * the description as well.
75 * Often, functors are only created as temporaries passed to algorithm
76 * calls, rather than being created as named variables.
78 * Two examples taken from the standard itself follow. To perform a
79 * by-element addition of two vectors @c a and @c b containing @c double,
80 * and put the result in @c a, use
82 * transform (a.begin(), a.end(), b.begin(), a.begin(), plus<double>());
84 * To negate every element in @c a, use
86 * transform(a.begin(), a.end(), a.begin(), negate<double>());
88 * The addition and negation functions will be inlined directly.
90 * The standard functors are derived from structs named @c unary_function
91 * and @c binary_function. These two classes contain nothing but typedefs,
92 * to aid in generic (template) programming. If you write your own
93 * functors, you might consider doing the same.
98 * This is one of the @link functors functor base classes@endlink.
100 template<typename _Arg, typename _Result>
101 struct unary_function
103 /// @c argument_type is the type of the argument
104 typedef _Arg argument_type;
106 /// @c result_type is the return type
107 typedef _Result result_type;
111 * This is one of the @link functors functor base classes@endlink.
113 template<typename _Arg1, typename _Arg2, typename _Result>
114 struct binary_function
116 /// @c first_argument_type is the type of the first argument
117 typedef _Arg1 first_argument_type;
119 /// @c second_argument_type is the type of the second argument
120 typedef _Arg2 second_argument_type;
122 /// @c result_type is the return type
123 typedef _Result result_type;
128 /** @defgroup arithmetic_functors Arithmetic Classes
131 * Because basic math often needs to be done during an algorithm,
132 * the library provides functors for those operations. See the
133 * documentation for @link functors the base classes@endlink
134 * for examples of their use.
138 /// One of the @link arithmetic_functors math functors@endlink.
139 template<typename _Tp>
140 struct plus : public binary_function<_Tp, _Tp, _Tp>
143 operator()(const _Tp& __x, const _Tp& __y) const
144 { return __x + __y; }
147 /// One of the @link arithmetic_functors math functors@endlink.
148 template<typename _Tp>
149 struct minus : public binary_function<_Tp, _Tp, _Tp>
152 operator()(const _Tp& __x, const _Tp& __y) const
153 { return __x - __y; }
156 /// One of the @link arithmetic_functors math functors@endlink.
157 template<typename _Tp>
158 struct multiplies : public binary_function<_Tp, _Tp, _Tp>
161 operator()(const _Tp& __x, const _Tp& __y) const
162 { return __x * __y; }
165 /// One of the @link arithmetic_functors math functors@endlink.
166 template<typename _Tp>
167 struct divides : public binary_function<_Tp, _Tp, _Tp>
170 operator()(const _Tp& __x, const _Tp& __y) const
171 { return __x / __y; }
174 /// One of the @link arithmetic_functors math functors@endlink.
175 template<typename _Tp>
176 struct modulus : public binary_function<_Tp, _Tp, _Tp>
179 operator()(const _Tp& __x, const _Tp& __y) const
180 { return __x % __y; }
183 /// One of the @link arithmetic_functors math functors@endlink.
184 template<typename _Tp>
185 struct negate : public unary_function<_Tp, _Tp>
188 operator()(const _Tp& __x) const
193 // 20.3.3 comparisons
194 /** @defgroup comparison_functors Comparison Classes
197 * The library provides six wrapper functors for all the basic comparisons
202 /// One of the @link comparison_functors comparison functors@endlink.
203 template<typename _Tp>
204 struct equal_to : public binary_function<_Tp, _Tp, bool>
207 operator()(const _Tp& __x, const _Tp& __y) const
208 { return __x == __y; }
211 /// One of the @link comparison_functors comparison functors@endlink.
212 template<typename _Tp>
213 struct not_equal_to : public binary_function<_Tp, _Tp, bool>
216 operator()(const _Tp& __x, const _Tp& __y) const
217 { return __x != __y; }
220 /// One of the @link comparison_functors comparison functors@endlink.
221 template<typename _Tp>
222 struct greater : public binary_function<_Tp, _Tp, bool>
225 operator()(const _Tp& __x, const _Tp& __y) const
226 { return __x > __y; }
229 /// One of the @link comparison_functors comparison functors@endlink.
230 template<typename _Tp>
231 struct less : public binary_function<_Tp, _Tp, bool>
234 operator()(const _Tp& __x, const _Tp& __y) const
235 { return __x < __y; }
238 /// One of the @link comparison_functors comparison functors@endlink.
239 template<typename _Tp>
240 struct greater_equal : public binary_function<_Tp, _Tp, bool>
243 operator()(const _Tp& __x, const _Tp& __y) const
244 { return __x >= __y; }
247 /// One of the @link comparison_functors comparison functors@endlink.
248 template<typename _Tp>
249 struct less_equal : public binary_function<_Tp, _Tp, bool>
252 operator()(const _Tp& __x, const _Tp& __y) const
253 { return __x <= __y; }
257 // 20.3.4 logical operations
258 /** @defgroup logical_functors Boolean Operations Classes
261 * Here are wrapper functors for Boolean operations: @c &&, @c ||,
266 /// One of the @link logical_functors Boolean operations functors@endlink.
267 template<typename _Tp>
268 struct logical_and : public binary_function<_Tp, _Tp, bool>
271 operator()(const _Tp& __x, const _Tp& __y) const
272 { return __x && __y; }
275 /// One of the @link logical_functors Boolean operations functors@endlink.
276 template<typename _Tp>
277 struct logical_or : public binary_function<_Tp, _Tp, bool>
280 operator()(const _Tp& __x, const _Tp& __y) const
281 { return __x || __y; }
284 /// One of the @link logical_functors Boolean operations functors@endlink.
285 template<typename _Tp>
286 struct logical_not : public unary_function<_Tp, bool>
289 operator()(const _Tp& __x) const
294 // _GLIBCXX_RESOLVE_LIB_DEFECTS
295 // DR 660. Missing Bitwise Operations.
296 template<typename _Tp>
297 struct bit_and : public binary_function<_Tp, _Tp, _Tp>
300 operator()(const _Tp& __x, const _Tp& __y) const
301 { return __x & __y; }
304 template<typename _Tp>
305 struct bit_or : public binary_function<_Tp, _Tp, _Tp>
308 operator()(const _Tp& __x, const _Tp& __y) const
309 { return __x | __y; }
312 template<typename _Tp>
313 struct bit_xor : public binary_function<_Tp, _Tp, _Tp>
316 operator()(const _Tp& __x, const _Tp& __y) const
317 { return __x ^ __y; }
321 /** @defgroup negators Negators
324 * The functions @c not1 and @c not2 each take a predicate functor
325 * and return an instance of @c unary_negate or
326 * @c binary_negate, respectively. These classes are functors whose
327 * @c operator() performs the stored predicate function and then returns
328 * the negation of the result.
330 * For example, given a vector of integers and a trivial predicate,
332 * struct IntGreaterThanThree
333 * : public std::unary_function<int, bool>
335 * bool operator() (int x) { return x > 3; }
338 * std::find_if (v.begin(), v.end(), not1(IntGreaterThanThree()));
340 * The call to @c find_if will locate the first index (i) of @c v for which
341 * <code>!(v[i] > 3)</code> is true.
343 * The not1/unary_negate combination works on predicates taking a single
344 * argument. The not2/binary_negate combination works on predicates which
345 * take two arguments.
349 /// One of the @link negators negation functors@endlink.
350 template<typename _Predicate>
352 : public unary_function<typename _Predicate::argument_type, bool>
359 unary_negate(const _Predicate& __x) : _M_pred(__x) { }
362 operator()(const typename _Predicate::argument_type& __x) const
363 { return !_M_pred(__x); }
366 /// One of the @link negators negation functors@endlink.
367 template<typename _Predicate>
368 inline unary_negate<_Predicate>
369 not1(const _Predicate& __pred)
370 { return unary_negate<_Predicate>(__pred); }
372 /// One of the @link negators negation functors@endlink.
373 template<typename _Predicate>
375 : public binary_function<typename _Predicate::first_argument_type,
376 typename _Predicate::second_argument_type, bool>
383 binary_negate(const _Predicate& __x) : _M_pred(__x) { }
386 operator()(const typename _Predicate::first_argument_type& __x,
387 const typename _Predicate::second_argument_type& __y) const
388 { return !_M_pred(__x, __y); }
391 /// One of the @link negators negation functors@endlink.
392 template<typename _Predicate>
393 inline binary_negate<_Predicate>
394 not2(const _Predicate& __pred)
395 { return binary_negate<_Predicate>(__pred); }
398 // 20.3.7 adaptors pointers functions
399 /** @defgroup pointer_adaptors Adaptors for pointers to functions
402 * The advantage of function objects over pointers to functions is that
403 * the objects in the standard library declare nested typedefs describing
404 * their argument and result types with uniform names (e.g., @c result_type
405 * from the base classes @c unary_function and @c binary_function).
406 * Sometimes those typedefs are required, not just optional.
408 * Adaptors are provided to turn pointers to unary (single-argument) and
409 * binary (double-argument) functions into function objects. The
410 * long-winded functor @c pointer_to_unary_function is constructed with a
411 * function pointer @c f, and its @c operator() called with argument @c x
412 * returns @c f(x). The functor @c pointer_to_binary_function does the same
413 * thing, but with a double-argument @c f and @c operator().
415 * The function @c ptr_fun takes a pointer-to-function @c f and constructs
416 * an instance of the appropriate functor.
420 /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
421 template<typename _Arg, typename _Result>
422 class pointer_to_unary_function : public unary_function<_Arg, _Result>
425 _Result (*_M_ptr)(_Arg);
428 pointer_to_unary_function() { }
431 pointer_to_unary_function(_Result (*__x)(_Arg))
435 operator()(_Arg __x) const
436 { return _M_ptr(__x); }
439 /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
440 template<typename _Arg, typename _Result>
441 inline pointer_to_unary_function<_Arg, _Result>
442 ptr_fun(_Result (*__x)(_Arg))
443 { return pointer_to_unary_function<_Arg, _Result>(__x); }
445 /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
446 template<typename _Arg1, typename _Arg2, typename _Result>
447 class pointer_to_binary_function
448 : public binary_function<_Arg1, _Arg2, _Result>
451 _Result (*_M_ptr)(_Arg1, _Arg2);
454 pointer_to_binary_function() { }
457 pointer_to_binary_function(_Result (*__x)(_Arg1, _Arg2))
461 operator()(_Arg1 __x, _Arg2 __y) const
462 { return _M_ptr(__x, __y); }
465 /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
466 template<typename _Arg1, typename _Arg2, typename _Result>
467 inline pointer_to_binary_function<_Arg1, _Arg2, _Result>
468 ptr_fun(_Result (*__x)(_Arg1, _Arg2))
469 { return pointer_to_binary_function<_Arg1, _Arg2, _Result>(__x); }
472 template<typename _Tp>
474 : public unary_function<_Tp,_Tp>
477 operator()(_Tp& __x) const
481 operator()(const _Tp& __x) const
485 template<typename _Pair>
487 : public unary_function<_Pair, typename _Pair::first_type>
489 typename _Pair::first_type&
490 operator()(_Pair& __x) const
491 { return __x.first; }
493 const typename _Pair::first_type&
494 operator()(const _Pair& __x) const
495 { return __x.first; }
497 #if __cplusplus >= 201103L
498 template<typename _Pair2>
499 typename _Pair2::first_type&
500 operator()(_Pair2& __x) const
501 { return __x.first; }
503 template<typename _Pair2>
504 const typename _Pair2::first_type&
505 operator()(const _Pair2& __x) const
506 { return __x.first; }
510 template<typename _Pair>
512 : public unary_function<_Pair, typename _Pair::second_type>
514 typename _Pair::second_type&
515 operator()(_Pair& __x) const
516 { return __x.second; }
518 const typename _Pair::second_type&
519 operator()(const _Pair& __x) const
520 { return __x.second; }
523 // 20.3.8 adaptors pointers members
524 /** @defgroup memory_adaptors Adaptors for pointers to members
527 * There are a total of 8 = 2^3 function objects in this family.
528 * (1) Member functions taking no arguments vs member functions taking
530 * (2) Call through pointer vs call through reference.
531 * (3) Const vs non-const member function.
533 * All of this complexity is in the function objects themselves. You can
534 * ignore it by using the helper function mem_fun and mem_fun_ref,
535 * which create whichever type of adaptor is appropriate.
539 /// One of the @link memory_adaptors adaptors for member
540 /// pointers@endlink.
541 template<typename _Ret, typename _Tp>
542 class mem_fun_t : public unary_function<_Tp*, _Ret>
546 mem_fun_t(_Ret (_Tp::*__pf)())
550 operator()(_Tp* __p) const
551 { return (__p->*_M_f)(); }
557 /// One of the @link memory_adaptors adaptors for member
558 /// pointers@endlink.
559 template<typename _Ret, typename _Tp>
560 class const_mem_fun_t : public unary_function<const _Tp*, _Ret>
564 const_mem_fun_t(_Ret (_Tp::*__pf)() const)
568 operator()(const _Tp* __p) const
569 { return (__p->*_M_f)(); }
572 _Ret (_Tp::*_M_f)() const;
575 /// One of the @link memory_adaptors adaptors for member
576 /// pointers@endlink.
577 template<typename _Ret, typename _Tp>
578 class mem_fun_ref_t : public unary_function<_Tp, _Ret>
582 mem_fun_ref_t(_Ret (_Tp::*__pf)())
586 operator()(_Tp& __r) const
587 { return (__r.*_M_f)(); }
593 /// One of the @link memory_adaptors adaptors for member
594 /// pointers@endlink.
595 template<typename _Ret, typename _Tp>
596 class const_mem_fun_ref_t : public unary_function<_Tp, _Ret>
600 const_mem_fun_ref_t(_Ret (_Tp::*__pf)() const)
604 operator()(const _Tp& __r) const
605 { return (__r.*_M_f)(); }
608 _Ret (_Tp::*_M_f)() const;
611 /// One of the @link memory_adaptors adaptors for member
612 /// pointers@endlink.
613 template<typename _Ret, typename _Tp, typename _Arg>
614 class mem_fun1_t : public binary_function<_Tp*, _Arg, _Ret>
618 mem_fun1_t(_Ret (_Tp::*__pf)(_Arg))
622 operator()(_Tp* __p, _Arg __x) const
623 { return (__p->*_M_f)(__x); }
626 _Ret (_Tp::*_M_f)(_Arg);
629 /// One of the @link memory_adaptors adaptors for member
630 /// pointers@endlink.
631 template<typename _Ret, typename _Tp, typename _Arg>
632 class const_mem_fun1_t : public binary_function<const _Tp*, _Arg, _Ret>
636 const_mem_fun1_t(_Ret (_Tp::*__pf)(_Arg) const)
640 operator()(const _Tp* __p, _Arg __x) const
641 { return (__p->*_M_f)(__x); }
644 _Ret (_Tp::*_M_f)(_Arg) const;
647 /// One of the @link memory_adaptors adaptors for member
648 /// pointers@endlink.
649 template<typename _Ret, typename _Tp, typename _Arg>
650 class mem_fun1_ref_t : public binary_function<_Tp, _Arg, _Ret>
654 mem_fun1_ref_t(_Ret (_Tp::*__pf)(_Arg))
658 operator()(_Tp& __r, _Arg __x) const
659 { return (__r.*_M_f)(__x); }
662 _Ret (_Tp::*_M_f)(_Arg);
665 /// One of the @link memory_adaptors adaptors for member
666 /// pointers@endlink.
667 template<typename _Ret, typename _Tp, typename _Arg>
668 class const_mem_fun1_ref_t : public binary_function<_Tp, _Arg, _Ret>
672 const_mem_fun1_ref_t(_Ret (_Tp::*__pf)(_Arg) const)
676 operator()(const _Tp& __r, _Arg __x) const
677 { return (__r.*_M_f)(__x); }
680 _Ret (_Tp::*_M_f)(_Arg) const;
683 // Mem_fun adaptor helper functions. There are only two:
684 // mem_fun and mem_fun_ref.
685 template<typename _Ret, typename _Tp>
686 inline mem_fun_t<_Ret, _Tp>
687 mem_fun(_Ret (_Tp::*__f)())
688 { return mem_fun_t<_Ret, _Tp>(__f); }
690 template<typename _Ret, typename _Tp>
691 inline const_mem_fun_t<_Ret, _Tp>
692 mem_fun(_Ret (_Tp::*__f)() const)
693 { return const_mem_fun_t<_Ret, _Tp>(__f); }
695 template<typename _Ret, typename _Tp>
696 inline mem_fun_ref_t<_Ret, _Tp>
697 mem_fun_ref(_Ret (_Tp::*__f)())
698 { return mem_fun_ref_t<_Ret, _Tp>(__f); }
700 template<typename _Ret, typename _Tp>
701 inline const_mem_fun_ref_t<_Ret, _Tp>
702 mem_fun_ref(_Ret (_Tp::*__f)() const)
703 { return const_mem_fun_ref_t<_Ret, _Tp>(__f); }
705 template<typename _Ret, typename _Tp, typename _Arg>
706 inline mem_fun1_t<_Ret, _Tp, _Arg>
707 mem_fun(_Ret (_Tp::*__f)(_Arg))
708 { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
710 template<typename _Ret, typename _Tp, typename _Arg>
711 inline const_mem_fun1_t<_Ret, _Tp, _Arg>
712 mem_fun(_Ret (_Tp::*__f)(_Arg) const)
713 { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
715 template<typename _Ret, typename _Tp, typename _Arg>
716 inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
717 mem_fun_ref(_Ret (_Tp::*__f)(_Arg))
718 { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
720 template<typename _Ret, typename _Tp, typename _Arg>
721 inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
722 mem_fun_ref(_Ret (_Tp::*__f)(_Arg) const)
723 { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
727 _GLIBCXX_END_NAMESPACE_VERSION
730 #if (__cplusplus < 201103L) || _GLIBCXX_USE_DEPRECATED
731 # include <backward/binders.h>
734 #endif /* _STL_FUNCTION_H */