1 // Functor implementations -*- C++ -*-
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52 /** @file stl_function.h
53 * This is an internal header file, included by other library headers.
54 * You should not attempt to use it directly.
57 #ifndef _STL_FUNCTION_H
58 #define _STL_FUNCTION_H 1
60 _GLIBCXX_BEGIN_NAMESPACE(std)
62 // 20.3.1 base classes
63 /** @defgroup functors Function Objects
66 * Function objects, or @e functors, are objects with an @c operator()
67 * defined and accessible. They can be passed as arguments to algorithm
68 * templates and used in place of a function pointer. Not only is the
69 * resulting expressiveness of the library increased, but the generated
70 * code can be more efficient than what you might write by hand. When we
71 * refer to @a functors, then, generally we include function pointers in
72 * the description as well.
74 * Often, functors are only created as temporaries passed to algorithm
75 * calls, rather than being created as named variables.
77 * Two examples taken from the standard itself follow. To perform a
78 * by-element addition of two vectors @c a and @c b containing @c double,
79 * and put the result in @c a, use
81 * transform (a.begin(), a.end(), b.begin(), a.begin(), plus<double>());
83 * To negate every element in @c a, use
85 * transform(a.begin(), a.end(), a.begin(), negate<double>());
87 * The addition and negation functions will be inlined directly.
89 * The standard functors are derived from structs named @c unary_function
90 * and @c binary_function. These two classes contain nothing but typedefs,
91 * to aid in generic (template) programming. If you write your own
92 * functors, you might consider doing the same.
97 * This is one of the @link functors functor base classes@endlink.
99 template<typename _Arg, typename _Result>
100 struct unary_function
102 typedef _Arg argument_type; ///< @c argument_type is the type of the
103 /// argument (no surprises here)
105 typedef _Result result_type; ///< @c result_type is the return type
109 * This is one of the @link functors functor base classes@endlink.
111 template<typename _Arg1, typename _Arg2, typename _Result>
112 struct binary_function
114 typedef _Arg1 first_argument_type; ///< the type of the first argument
115 /// (no surprises here)
117 typedef _Arg2 second_argument_type; ///< the type of the second argument
118 typedef _Result result_type; ///< type of the return type
123 /** @defgroup arithmetic_functors Arithmetic Classes
126 * Because basic math often needs to be done during an algorithm,
127 * the library provides functors for those operations. See the
128 * documentation for @link functors the base classes@endlink
129 * for examples of their use.
133 /// One of the @link arithmetic_functors math functors@endlink.
134 template<typename _Tp>
135 struct plus : public binary_function<_Tp, _Tp, _Tp>
138 operator()(const _Tp& __x, const _Tp& __y) const
139 { return __x + __y; }
142 /// One of the @link arithmetic_functors math functors@endlink.
143 template<typename _Tp>
144 struct minus : public binary_function<_Tp, _Tp, _Tp>
147 operator()(const _Tp& __x, const _Tp& __y) const
148 { return __x - __y; }
151 /// One of the @link arithmetic_functors math functors@endlink.
152 template<typename _Tp>
153 struct multiplies : public binary_function<_Tp, _Tp, _Tp>
156 operator()(const _Tp& __x, const _Tp& __y) const
157 { return __x * __y; }
160 /// One of the @link arithmetic_functors math functors@endlink.
161 template<typename _Tp>
162 struct divides : public binary_function<_Tp, _Tp, _Tp>
165 operator()(const _Tp& __x, const _Tp& __y) const
166 { return __x / __y; }
169 /// One of the @link arithmetic_functors math functors@endlink.
170 template<typename _Tp>
171 struct modulus : public binary_function<_Tp, _Tp, _Tp>
174 operator()(const _Tp& __x, const _Tp& __y) const
175 { return __x % __y; }
178 /// One of the @link arithmetic_functors math functors@endlink.
179 template<typename _Tp>
180 struct negate : public unary_function<_Tp, _Tp>
183 operator()(const _Tp& __x) const
188 // 20.3.3 comparisons
189 /** @defgroup comparison_functors Comparison Classes
192 * The library provides six wrapper functors for all the basic comparisons
197 /// One of the @link comparison_functors comparison functors@endlink.
198 template<typename _Tp>
199 struct equal_to : public binary_function<_Tp, _Tp, bool>
202 operator()(const _Tp& __x, const _Tp& __y) const
203 { return __x == __y; }
206 /// One of the @link comparison_functors comparison functors@endlink.
207 template<typename _Tp>
208 struct not_equal_to : public binary_function<_Tp, _Tp, bool>
211 operator()(const _Tp& __x, const _Tp& __y) const
212 { return __x != __y; }
215 /// One of the @link comparison_functors comparison functors@endlink.
216 template<typename _Tp>
217 struct greater : public binary_function<_Tp, _Tp, bool>
220 operator()(const _Tp& __x, const _Tp& __y) const
221 { return __x > __y; }
224 /// One of the @link comparison_functors comparison functors@endlink.
225 template<typename _Tp>
226 struct less : public binary_function<_Tp, _Tp, bool>
229 operator()(const _Tp& __x, const _Tp& __y) const
230 { return __x < __y; }
233 /// One of the @link comparison_functors comparison functors@endlink.
234 template<typename _Tp>
235 struct greater_equal : public binary_function<_Tp, _Tp, bool>
238 operator()(const _Tp& __x, const _Tp& __y) const
239 { return __x >= __y; }
242 /// One of the @link comparison_functors comparison functors@endlink.
243 template<typename _Tp>
244 struct less_equal : public binary_function<_Tp, _Tp, bool>
247 operator()(const _Tp& __x, const _Tp& __y) const
248 { return __x <= __y; }
252 // 20.3.4 logical operations
253 /** @defgroup logical_functors Boolean Operations Classes
256 * Here are wrapper functors for Boolean operations: @c &&, @c ||,
261 /// One of the @link logical_functors Boolean operations functors@endlink.
262 template<typename _Tp>
263 struct logical_and : public binary_function<_Tp, _Tp, bool>
266 operator()(const _Tp& __x, const _Tp& __y) const
267 { return __x && __y; }
270 /// One of the @link logical_functors Boolean operations functors@endlink.
271 template<typename _Tp>
272 struct logical_or : public binary_function<_Tp, _Tp, bool>
275 operator()(const _Tp& __x, const _Tp& __y) const
276 { return __x || __y; }
279 /// One of the @link logical_functors Boolean operations functors@endlink.
280 template<typename _Tp>
281 struct logical_not : public unary_function<_Tp, bool>
284 operator()(const _Tp& __x) const
289 // _GLIBCXX_RESOLVE_LIB_DEFECTS
290 // DR 660. Missing Bitwise Operations.
291 template<typename _Tp>
292 struct bit_and : public binary_function<_Tp, _Tp, _Tp>
295 operator()(const _Tp& __x, const _Tp& __y) const
296 { return __x & __y; }
299 template<typename _Tp>
300 struct bit_or : public binary_function<_Tp, _Tp, _Tp>
303 operator()(const _Tp& __x, const _Tp& __y) const
304 { return __x | __y; }
307 template<typename _Tp>
308 struct bit_xor : public binary_function<_Tp, _Tp, _Tp>
311 operator()(const _Tp& __x, const _Tp& __y) const
312 { return __x ^ __y; }
316 /** @defgroup negators Negators
319 * The functions @c not1 and @c not2 each take a predicate functor
320 * and return an instance of @c unary_negate or
321 * @c binary_negate, respectively. These classes are functors whose
322 * @c operator() performs the stored predicate function and then returns
323 * the negation of the result.
325 * For example, given a vector of integers and a trivial predicate,
327 * struct IntGreaterThanThree
328 * : public std::unary_function<int, bool>
330 * bool operator() (int x) { return x > 3; }
333 * std::find_if (v.begin(), v.end(), not1(IntGreaterThanThree()));
335 * The call to @c find_if will locate the first index (i) of @c v for which
336 * <code>!(v[i] > 3)</code> is true.
338 * The not1/unary_negate combination works on predicates taking a single
339 * argument. The not2/binary_negate combination works on predicates which
340 * take two arguments.
344 /// One of the @link negators negation functors@endlink.
345 template<typename _Predicate>
347 : public unary_function<typename _Predicate::argument_type, bool>
354 unary_negate(const _Predicate& __x) : _M_pred(__x) { }
357 operator()(const typename _Predicate::argument_type& __x) const
358 { return !_M_pred(__x); }
361 /// One of the @link negators negation functors@endlink.
362 template<typename _Predicate>
363 inline unary_negate<_Predicate>
364 not1(const _Predicate& __pred)
365 { return unary_negate<_Predicate>(__pred); }
367 /// One of the @link negators negation functors@endlink.
368 template<typename _Predicate>
370 : public binary_function<typename _Predicate::first_argument_type,
371 typename _Predicate::second_argument_type, bool>
378 binary_negate(const _Predicate& __x) : _M_pred(__x) { }
381 operator()(const typename _Predicate::first_argument_type& __x,
382 const typename _Predicate::second_argument_type& __y) const
383 { return !_M_pred(__x, __y); }
386 /// One of the @link negators negation functors@endlink.
387 template<typename _Predicate>
388 inline binary_negate<_Predicate>
389 not2(const _Predicate& __pred)
390 { return binary_negate<_Predicate>(__pred); }
393 // 20.3.7 adaptors pointers functions
394 /** @defgroup pointer_adaptors Adaptors for pointers to functions
397 * The advantage of function objects over pointers to functions is that
398 * the objects in the standard library declare nested typedefs describing
399 * their argument and result types with uniform names (e.g., @c result_type
400 * from the base classes @c unary_function and @c binary_function).
401 * Sometimes those typedefs are required, not just optional.
403 * Adaptors are provided to turn pointers to unary (single-argument) and
404 * binary (double-argument) functions into function objects. The
405 * long-winded functor @c pointer_to_unary_function is constructed with a
406 * function pointer @c f, and its @c operator() called with argument @c x
407 * returns @c f(x). The functor @c pointer_to_binary_function does the same
408 * thing, but with a double-argument @c f and @c operator().
410 * The function @c ptr_fun takes a pointer-to-function @c f and constructs
411 * an instance of the appropriate functor.
415 /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
416 template<typename _Arg, typename _Result>
417 class pointer_to_unary_function : public unary_function<_Arg, _Result>
420 _Result (*_M_ptr)(_Arg);
423 pointer_to_unary_function() { }
426 pointer_to_unary_function(_Result (*__x)(_Arg))
430 operator()(_Arg __x) const
431 { return _M_ptr(__x); }
434 /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
435 template<typename _Arg, typename _Result>
436 inline pointer_to_unary_function<_Arg, _Result>
437 ptr_fun(_Result (*__x)(_Arg))
438 { return pointer_to_unary_function<_Arg, _Result>(__x); }
440 /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
441 template<typename _Arg1, typename _Arg2, typename _Result>
442 class pointer_to_binary_function
443 : public binary_function<_Arg1, _Arg2, _Result>
446 _Result (*_M_ptr)(_Arg1, _Arg2);
449 pointer_to_binary_function() { }
452 pointer_to_binary_function(_Result (*__x)(_Arg1, _Arg2))
456 operator()(_Arg1 __x, _Arg2 __y) const
457 { return _M_ptr(__x, __y); }
460 /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
461 template<typename _Arg1, typename _Arg2, typename _Result>
462 inline pointer_to_binary_function<_Arg1, _Arg2, _Result>
463 ptr_fun(_Result (*__x)(_Arg1, _Arg2))
464 { return pointer_to_binary_function<_Arg1, _Arg2, _Result>(__x); }
467 template<typename _Tp>
468 struct _Identity : public unary_function<_Tp,_Tp>
471 operator()(_Tp& __x) const
475 operator()(const _Tp& __x) const
479 template<typename _Pair>
480 struct _Select1st : public unary_function<_Pair,
481 typename _Pair::first_type>
483 typename _Pair::first_type&
484 operator()(_Pair& __x) const
485 { return __x.first; }
487 const typename _Pair::first_type&
488 operator()(const _Pair& __x) const
489 { return __x.first; }
491 #ifdef __GXX_EXPERIMENTAL_CXX0X__
492 template<typename _Pair2>
493 typename _Pair2::first_type&
494 operator()(_Pair2& __x) const
495 { return __x.first; }
497 template<typename _Pair2>
498 const typename _Pair2::first_type&
499 operator()(const _Pair2& __x) const
500 { return __x.first; }
504 template<typename _Pair>
505 struct _Select2nd : public unary_function<_Pair,
506 typename _Pair::second_type>
508 typename _Pair::second_type&
509 operator()(_Pair& __x) const
510 { return __x.second; }
512 const typename _Pair::second_type&
513 operator()(const _Pair& __x) const
514 { return __x.second; }
517 // 20.3.8 adaptors pointers members
518 /** @defgroup memory_adaptors Adaptors for pointers to members
521 * There are a total of 8 = 2^3 function objects in this family.
522 * (1) Member functions taking no arguments vs member functions taking
524 * (2) Call through pointer vs call through reference.
525 * (3) Const vs non-const member function.
527 * All of this complexity is in the function objects themselves. You can
528 * ignore it by using the helper function mem_fun and mem_fun_ref,
529 * which create whichever type of adaptor is appropriate.
533 /// One of the @link memory_adaptors adaptors for member
534 /// pointers@endlink.
535 template<typename _Ret, typename _Tp>
536 class mem_fun_t : public unary_function<_Tp*, _Ret>
540 mem_fun_t(_Ret (_Tp::*__pf)())
544 operator()(_Tp* __p) const
545 { return (__p->*_M_f)(); }
551 /// One of the @link memory_adaptors adaptors for member
552 /// pointers@endlink.
553 template<typename _Ret, typename _Tp>
554 class const_mem_fun_t : public unary_function<const _Tp*, _Ret>
558 const_mem_fun_t(_Ret (_Tp::*__pf)() const)
562 operator()(const _Tp* __p) const
563 { return (__p->*_M_f)(); }
566 _Ret (_Tp::*_M_f)() const;
569 /// One of the @link memory_adaptors adaptors for member
570 /// pointers@endlink.
571 template<typename _Ret, typename _Tp>
572 class mem_fun_ref_t : public unary_function<_Tp, _Ret>
576 mem_fun_ref_t(_Ret (_Tp::*__pf)())
580 operator()(_Tp& __r) const
581 { return (__r.*_M_f)(); }
587 /// One of the @link memory_adaptors adaptors for member
588 /// pointers@endlink.
589 template<typename _Ret, typename _Tp>
590 class const_mem_fun_ref_t : public unary_function<_Tp, _Ret>
594 const_mem_fun_ref_t(_Ret (_Tp::*__pf)() const)
598 operator()(const _Tp& __r) const
599 { return (__r.*_M_f)(); }
602 _Ret (_Tp::*_M_f)() const;
605 /// One of the @link memory_adaptors adaptors for member
606 /// pointers@endlink.
607 template<typename _Ret, typename _Tp, typename _Arg>
608 class mem_fun1_t : public binary_function<_Tp*, _Arg, _Ret>
612 mem_fun1_t(_Ret (_Tp::*__pf)(_Arg))
616 operator()(_Tp* __p, _Arg __x) const
617 { return (__p->*_M_f)(__x); }
620 _Ret (_Tp::*_M_f)(_Arg);
623 /// One of the @link memory_adaptors adaptors for member
624 /// pointers@endlink.
625 template<typename _Ret, typename _Tp, typename _Arg>
626 class const_mem_fun1_t : public binary_function<const _Tp*, _Arg, _Ret>
630 const_mem_fun1_t(_Ret (_Tp::*__pf)(_Arg) const)
634 operator()(const _Tp* __p, _Arg __x) const
635 { return (__p->*_M_f)(__x); }
638 _Ret (_Tp::*_M_f)(_Arg) const;
641 /// One of the @link memory_adaptors adaptors for member
642 /// pointers@endlink.
643 template<typename _Ret, typename _Tp, typename _Arg>
644 class mem_fun1_ref_t : public binary_function<_Tp, _Arg, _Ret>
648 mem_fun1_ref_t(_Ret (_Tp::*__pf)(_Arg))
652 operator()(_Tp& __r, _Arg __x) const
653 { return (__r.*_M_f)(__x); }
656 _Ret (_Tp::*_M_f)(_Arg);
659 /// One of the @link memory_adaptors adaptors for member
660 /// pointers@endlink.
661 template<typename _Ret, typename _Tp, typename _Arg>
662 class const_mem_fun1_ref_t : public binary_function<_Tp, _Arg, _Ret>
666 const_mem_fun1_ref_t(_Ret (_Tp::*__pf)(_Arg) const)
670 operator()(const _Tp& __r, _Arg __x) const
671 { return (__r.*_M_f)(__x); }
674 _Ret (_Tp::*_M_f)(_Arg) const;
677 // Mem_fun adaptor helper functions. There are only two:
678 // mem_fun and mem_fun_ref.
679 template<typename _Ret, typename _Tp>
680 inline mem_fun_t<_Ret, _Tp>
681 mem_fun(_Ret (_Tp::*__f)())
682 { return mem_fun_t<_Ret, _Tp>(__f); }
684 template<typename _Ret, typename _Tp>
685 inline const_mem_fun_t<_Ret, _Tp>
686 mem_fun(_Ret (_Tp::*__f)() const)
687 { return const_mem_fun_t<_Ret, _Tp>(__f); }
689 template<typename _Ret, typename _Tp>
690 inline mem_fun_ref_t<_Ret, _Tp>
691 mem_fun_ref(_Ret (_Tp::*__f)())
692 { return mem_fun_ref_t<_Ret, _Tp>(__f); }
694 template<typename _Ret, typename _Tp>
695 inline const_mem_fun_ref_t<_Ret, _Tp>
696 mem_fun_ref(_Ret (_Tp::*__f)() const)
697 { return const_mem_fun_ref_t<_Ret, _Tp>(__f); }
699 template<typename _Ret, typename _Tp, typename _Arg>
700 inline mem_fun1_t<_Ret, _Tp, _Arg>
701 mem_fun(_Ret (_Tp::*__f)(_Arg))
702 { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
704 template<typename _Ret, typename _Tp, typename _Arg>
705 inline const_mem_fun1_t<_Ret, _Tp, _Arg>
706 mem_fun(_Ret (_Tp::*__f)(_Arg) const)
707 { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
709 template<typename _Ret, typename _Tp, typename _Arg>
710 inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
711 mem_fun_ref(_Ret (_Tp::*__f)(_Arg))
712 { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
714 template<typename _Ret, typename _Tp, typename _Arg>
715 inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
716 mem_fun_ref(_Ret (_Tp::*__f)(_Arg) const)
717 { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
721 _GLIBCXX_END_NAMESPACE
723 #if !defined(__GXX_EXPERIMENTAL_CXX0X__) || _GLIBCXX_DEPRECATED
724 # include <backward/binders.h>
727 #endif /* _STL_FUNCTION_H */