libstdc++-v3/include/bits/stl_function.h

   1 // Functor implementations -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009, 2010,
   4 // 2011, 2012
   5 // Free Software Foundation, Inc.
   6 //
   7 // This file is part of the GNU ISO C++ Library.  This library is free
   8 // software; you can redistribute it and/or modify it under the
   9 // terms of the GNU General Public License as published by the
  10 // Free Software Foundation; either version 3, or (at your option)
  11 // any later version.
  12
  13 // This library is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // Under Section 7 of GPL version 3, you are granted additional
  19 // permissions described in the GCC Runtime Library Exception, version
  20 // 3.1, as published by the Free Software Foundation.
  21
  22 // You should have received a copy of the GNU General Public License and
  23 // a copy of the GCC Runtime Library Exception along with this program;
  24 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  25 // <http://www.gnu.org/licenses/>.
  26
  27 /*
  28  *
  29  * Copyright (c) 1994
  30  * Hewlett-Packard Company
  31  *
  32  * Permission to use, copy, modify, distribute and sell this software
  33  * and its documentation for any purpose is hereby granted without fee,
  34  * provided that the above copyright notice appear in all copies and
  35  * that both that copyright notice and this permission notice appear
  36  * in supporting documentation.  Hewlett-Packard Company makes no
  37  * representations about the suitability of this software for any
  38  * purpose.  It is provided "as is" without express or implied warranty.
  39  *
  40  *
  41  * Copyright (c) 1996-1998
  42  * Silicon Graphics Computer Systems, Inc.
  43  *
  44  * Permission to use, copy, modify, distribute and sell this software
  45  * and its documentation for any purpose is hereby granted without fee,
  46  * provided that the above copyright notice appear in all copies and
  47  * that both that copyright notice and this permission notice appear
  48  * in supporting documentation.  Silicon Graphics makes no
  49  * representations about the suitability of this software for any
  50  * purpose.  It is provided "as is" without express or implied warranty.
  51  */
  52
  53 /** @file bits/stl_function.h
  54  *  This is an internal header file, included by other library headers.
  55  *  Do not attempt to use it directly. @headername{functional}
  56  */
  57
  58 #ifndef _STL_FUNCTION_H
  59 #define _STL_FUNCTION_H 1
  60
  61 namespace std _GLIBCXX_VISIBILITY(default)
  62 {
  63 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  64
  65   // 20.3.1 base classes
  66   /** @defgroup functors Function Objects
  67    * @ingroup utilities
  68    *
  69    *  Function objects, or @e functors, are objects with an @c operator()
  70    *  defined and accessible.  They can be passed as arguments to algorithm
  71    *  templates and used in place of a function pointer.  Not only is the
  72    *  resulting expressiveness of the library increased, but the generated
  73    *  code can be more efficient than what you might write by hand.  When we
  74    *  refer to @a functors, then, generally we include function pointers in
  75    *  the description as well.
  76    *
  77    *  Often, functors are only created as temporaries passed to algorithm
  78    *  calls, rather than being created as named variables.
  79    *
  80    *  Two examples taken from the standard itself follow.  To perform a
  81    *  by-element addition of two vectors @c a and @c b containing @c double,
  82    *  and put the result in @c a, use
  83    *  \code
  84    *  transform (a.begin(), a.end(), b.begin(), a.begin(), plus<double>());
  85    *  \endcode
  86    *  To negate every element in @c a, use
  87    *  \code
  88    *  transform(a.begin(), a.end(), a.begin(), negate<double>());
  89    *  \endcode
  90    *  The addition and negation functions will be inlined directly.
  91    *
  92    *  The standard functors are derived from structs named @c unary_function
  93    *  and @c binary_function.  These two classes contain nothing but typedefs,
  94    *  to aid in generic (template) programming.  If you write your own
  95    *  functors, you might consider doing the same.
  96    *
  97    *  @{
  98    */
  99   /**
 100    *  This is one of the @link functors functor base classes@endlink.
 101    */
 102   template<typename _Arg, typename _Result>
 103     struct unary_function
 104     {
 105       /// @c argument_type is the type of the argument
 106       typedef _Arg      argument_type;
 107
 108       /// @c result_type is the return type
 109       typedef _Result   result_type;
 110     };
 111
 112   /**
 113    *  This is one of the @link functors functor base classes@endlink.
 114    */
 115   template<typename _Arg1, typename _Arg2, typename _Result>
 116     struct binary_function
 117     {
 118       /// @c first_argument_type is the type of the first argument
 119       typedef _Arg1     first_argument_type;
 120
 121       /// @c second_argument_type is the type of the second argument
 122       typedef _Arg2     second_argument_type;
 123
 124       /// @c result_type is the return type
 125       typedef _Result   result_type;
 126     };
 127   /** @}  */
 128
 129   // 20.3.2 arithmetic
 130   /** @defgroup arithmetic_functors Arithmetic Classes
 131    * @ingroup functors
 132    *
 133    *  Because basic math often needs to be done during an algorithm,
 134    *  the library provides functors for those operations.  See the
 135    *  documentation for @link functors the base classes@endlink
 136    *  for examples of their use.
 137    *
 138    *  @{
 139    */
 140   /// One of the @link arithmetic_functors math functors@endlink.
 141   template<typename _Tp>
 142     struct plus : public binary_function<_Tp, _Tp, _Tp>
 143     {
 144       _Tp
 145       operator()(const _Tp& __x, const _Tp& __y) const
 146       { return __x + __y; }
 147     };
 148
 149   /// One of the @link arithmetic_functors math functors@endlink.
 150   template<typename _Tp>
 151     struct minus : public binary_function<_Tp, _Tp, _Tp>
 152     {
 153       _Tp
 154       operator()(const _Tp& __x, const _Tp& __y) const
 155       { return __x - __y; }
 156     };
 157
 158   /// One of the @link arithmetic_functors math functors@endlink.
 159   template<typename _Tp>
 160     struct multiplies : public binary_function<_Tp, _Tp, _Tp>
 161     {
 162       _Tp
 163       operator()(const _Tp& __x, const _Tp& __y) const
 164       { return __x * __y; }
 165     };
 166
 167   /// One of the @link arithmetic_functors math functors@endlink.
 168   template<typename _Tp>
 169     struct divides : public binary_function<_Tp, _Tp, _Tp>
 170     {
 171       _Tp
 172       operator()(const _Tp& __x, const _Tp& __y) const
 173       { return __x / __y; }
 174     };
 175
 176   /// One of the @link arithmetic_functors math functors@endlink.
 177   template<typename _Tp>
 178     struct modulus : public binary_function<_Tp, _Tp, _Tp>
 179     {
 180       _Tp
 181       operator()(const _Tp& __x, const _Tp& __y) const
 182       { return __x % __y; }
 183     };
 184
 185   /// One of the @link arithmetic_functors math functors@endlink.
 186   template<typename _Tp>
 187     struct negate : public unary_function<_Tp, _Tp>
 188     {
 189       _Tp
 190       operator()(const _Tp& __x) const
 191       { return -__x; }
 192     };
 193   /** @}  */
 194
 195   // 20.3.3 comparisons
 196   /** @defgroup comparison_functors Comparison Classes
 197    * @ingroup functors
 198    *
 199    *  The library provides six wrapper functors for all the basic comparisons
 200    *  in C++, like @c <.
 201    *
 202    *  @{
 203    */
 204   /// One of the @link comparison_functors comparison functors@endlink.
 205   template<typename _Tp>
 206     struct equal_to : public binary_function<_Tp, _Tp, bool>
 207     {
 208       bool
 209       operator()(const _Tp& __x, const _Tp& __y) const
 210       { return __x == __y; }
 211     };
 212
 213   /// One of the @link comparison_functors comparison functors@endlink.
 214   template<typename _Tp>
 215     struct not_equal_to : public binary_function<_Tp, _Tp, bool>
 216     {
 217       bool
 218       operator()(const _Tp& __x, const _Tp& __y) const
 219       { return __x != __y; }
 220     };
 221
 222   /// One of the @link comparison_functors comparison functors@endlink.
 223   template<typename _Tp>
 224     struct greater : public binary_function<_Tp, _Tp, bool>
 225     {
 226       bool
 227       operator()(const _Tp& __x, const _Tp& __y) const
 228       { return __x > __y; }
 229     };
 230
 231   /// One of the @link comparison_functors comparison functors@endlink.
 232   template<typename _Tp>
 233     struct less : public binary_function<_Tp, _Tp, bool>
 234     {
 235       bool
 236       operator()(const _Tp& __x, const _Tp& __y) const
 237       { return __x < __y; }
 238     };
 239
 240   /// One of the @link comparison_functors comparison functors@endlink.
 241   template<typename _Tp>
 242     struct greater_equal : public binary_function<_Tp, _Tp, bool>
 243     {
 244       bool
 245       operator()(const _Tp& __x, const _Tp& __y) const
 246       { return __x >= __y; }
 247     };
 248
 249   /// One of the @link comparison_functors comparison functors@endlink.
 250   template<typename _Tp>
 251     struct less_equal : public binary_function<_Tp, _Tp, bool>
 252     {
 253       bool
 254       operator()(const _Tp& __x, const _Tp& __y) const
 255       { return __x <= __y; }
 256     };
 257   /** @}  */
 258
 259   // 20.3.4 logical operations
 260   /** @defgroup logical_functors Boolean Operations Classes
 261    * @ingroup functors
 262    *
 263    *  Here are wrapper functors for Boolean operations: @c &&, @c ||,
 264    *  and @c !.
 265    *
 266    *  @{
 267    */
 268   /// One of the @link logical_functors Boolean operations functors@endlink.
 269   template<typename _Tp>
 270     struct logical_and : public binary_function<_Tp, _Tp, bool>
 271     {
 272       bool
 273       operator()(const _Tp& __x, const _Tp& __y) const
 274       { return __x && __y; }
 275     };
 276
 277   /// One of the @link logical_functors Boolean operations functors@endlink.
 278   template<typename _Tp>
 279     struct logical_or : public binary_function<_Tp, _Tp, bool>
 280     {
 281       bool
 282       operator()(const _Tp& __x, const _Tp& __y) const
 283       { return __x || __y; }
 284     };
 285
 286   /// One of the @link logical_functors Boolean operations functors@endlink.
 287   template<typename _Tp>
 288     struct logical_not : public unary_function<_Tp, bool>
 289     {
 290       bool
 291       operator()(const _Tp& __x) const
 292       { return !__x; }
 293     };
 294   /** @}  */
 295
 296   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 297   // DR 660. Missing Bitwise Operations.
 298   template<typename _Tp>
 299     struct bit_and : public binary_function<_Tp, _Tp, _Tp>
 300     {
 301       _Tp
 302       operator()(const _Tp& __x, const _Tp& __y) const
 303       { return __x & __y; }
 304     };
 305
 306   template<typename _Tp>
 307     struct bit_or : public binary_function<_Tp, _Tp, _Tp>
 308     {
 309       _Tp
 310       operator()(const _Tp& __x, const _Tp& __y) const
 311       { return __x | __y; }
 312     };
 313
 314   template<typename _Tp>
 315     struct bit_xor : public binary_function<_Tp, _Tp, _Tp>
 316     {
 317       _Tp
 318       operator()(const _Tp& __x, const _Tp& __y) const
 319       { return __x ^ __y; }
 320     };
 321
 322   // 20.3.5 negators
 323   /** @defgroup negators Negators
 324    * @ingroup functors
 325    *
 326    *  The functions @c not1 and @c not2 each take a predicate functor
 327    *  and return an instance of @c unary_negate or
 328    *  @c binary_negate, respectively.  These classes are functors whose
 329    *  @c operator() performs the stored predicate function and then returns
 330    *  the negation of the result.
 331    *
 332    *  For example, given a vector of integers and a trivial predicate,
 333    *  \code
 334    *  struct IntGreaterThanThree
 335    *    : public std::unary_function<int, bool>
 336    *  {
 337    *      bool operator() (int x) { return x > 3; }
 338    *  };
 339    *
 340    *  std::find_if (v.begin(), v.end(), not1(IntGreaterThanThree()));
 341    *  \endcode
 342    *  The call to @c find_if will locate the first index (i) of @c v for which
 343    *  <code>!(v[i] > 3)</code> is true.
 344    *
 345    *  The not1/unary_negate combination works on predicates taking a single
 346    *  argument.  The not2/binary_negate combination works on predicates which
 347    *  take two arguments.
 348    *
 349    *  @{
 350    */
 351   /// One of the @link negators negation functors@endlink.
 352   template<typename _Predicate>
 353     class unary_negate
 354     : public unary_function<typename _Predicate::argument_type, bool>
 355     {
 356     protected:
 357       _Predicate _M_pred;
 358
 359     public:
 360       explicit
 361       unary_negate(const _Predicate& __x) : _M_pred(__x) { }
 362
 363       bool
 364       operator()(const typename _Predicate::argument_type& __x) const
 365       { return !_M_pred(__x); }
 366     };
 367
 368   /// One of the @link negators negation functors@endlink.
 369   template<typename _Predicate>
 370     inline unary_negate<_Predicate>
 371     not1(const _Predicate& __pred)
 372     { return unary_negate<_Predicate>(__pred); }
 373
 374   /// One of the @link negators negation functors@endlink.
 375   template<typename _Predicate>
 376     class binary_negate
 377     : public binary_function<typename _Predicate::first_argument_type,
 378                              typename _Predicate::second_argument_type, bool>
 379     {
 380     protected:
 381       _Predicate _M_pred;
 382
 383     public:
 384       explicit
 385       binary_negate(const _Predicate& __x) : _M_pred(__x) { }
 386
 387       bool
 388       operator()(const typename _Predicate::first_argument_type& __x,
 389                  const typename _Predicate::second_argument_type& __y) const
 390       { return !_M_pred(__x, __y); }
 391     };
 392
 393   /// One of the @link negators negation functors@endlink.
 394   template<typename _Predicate>
 395     inline binary_negate<_Predicate>
 396     not2(const _Predicate& __pred)
 397     { return binary_negate<_Predicate>(__pred); }
 398   /** @}  */
 399
 400   // 20.3.7 adaptors pointers functions
 401   /** @defgroup pointer_adaptors Adaptors for pointers to functions
 402    * @ingroup functors
 403    *
 404    *  The advantage of function objects over pointers to functions is that
 405    *  the objects in the standard library declare nested typedefs describing
 406    *  their argument and result types with uniform names (e.g., @c result_type
 407    *  from the base classes @c unary_function and @c binary_function).
 408    *  Sometimes those typedefs are required, not just optional.
 409    *
 410    *  Adaptors are provided to turn pointers to unary (single-argument) and
 411    *  binary (double-argument) functions into function objects.  The
 412    *  long-winded functor @c pointer_to_unary_function is constructed with a
 413    *  function pointer @c f, and its @c operator() called with argument @c x
 414    *  returns @c f(x).  The functor @c pointer_to_binary_function does the same
 415    *  thing, but with a double-argument @c f and @c operator().
 416    *
 417    *  The function @c ptr_fun takes a pointer-to-function @c f and constructs
 418    *  an instance of the appropriate functor.
 419    *
 420    *  @{
 421    */
 422   /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
 423   template<typename _Arg, typename _Result>
 424     class pointer_to_unary_function : public unary_function<_Arg, _Result>
 425     {
 426     protected:
 427       _Result (*_M_ptr)(_Arg);
 428
 429     public:
 430       pointer_to_unary_function() { }
 431
 432       explicit
 433       pointer_to_unary_function(_Result (*__x)(_Arg))
 434       : _M_ptr(__x) { }
 435
 436       _Result
 437       operator()(_Arg __x) const
 438       { return _M_ptr(__x); }
 439     };
 440
 441   /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
 442   template<typename _Arg, typename _Result>
 443     inline pointer_to_unary_function<_Arg, _Result>
 444     ptr_fun(_Result (*__x)(_Arg))
 445     { return pointer_to_unary_function<_Arg, _Result>(__x); }
 446
 447   /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
 448   template<typename _Arg1, typename _Arg2, typename _Result>
 449     class pointer_to_binary_function
 450     : public binary_function<_Arg1, _Arg2, _Result>
 451     {
 452     protected:
 453       _Result (*_M_ptr)(_Arg1, _Arg2);
 454
 455     public:
 456       pointer_to_binary_function() { }
 457
 458       explicit
 459       pointer_to_binary_function(_Result (*__x)(_Arg1, _Arg2))
 460       : _M_ptr(__x) { }
 461
 462       _Result
 463       operator()(_Arg1 __x, _Arg2 __y) const
 464       { return _M_ptr(__x, __y); }
 465     };
 466
 467   /// One of the @link pointer_adaptors adaptors for function pointers@endlink.
 468   template<typename _Arg1, typename _Arg2, typename _Result>
 469     inline pointer_to_binary_function<_Arg1, _Arg2, _Result>
 470     ptr_fun(_Result (*__x)(_Arg1, _Arg2))
 471     { return pointer_to_binary_function<_Arg1, _Arg2, _Result>(__x); }
 472   /** @}  */
 473
 474   template<typename _Tp>
 475     struct _Identity
 476     : public unary_function<_Tp,_Tp>
 477     {
 478       _Tp&
 479       operator()(_Tp& __x) const
 480       { return __x; }
 481
 482       const _Tp&
 483       operator()(const _Tp& __x) const
 484       { return __x; }
 485     };
 486
 487   template<typename _Pair>
 488     struct _Select1st
 489     : public unary_function<_Pair, typename _Pair::first_type>
 490     {
 491       typename _Pair::first_type&
 492       operator()(_Pair& __x) const
 493       { return __x.first; }
 494
 495       const typename _Pair::first_type&
 496       operator()(const _Pair& __x) const
 497       { return __x.first; }
 498
 499 #if __cplusplus >= 201103L
 500       template<typename _Pair2>
 501         typename _Pair2::first_type&
 502         operator()(_Pair2& __x) const
 503         { return __x.first; }
 504
 505       template<typename _Pair2>
 506         const typename _Pair2::first_type&
 507         operator()(const _Pair2& __x) const
 508         { return __x.first; }
 509 #endif
 510     };
 511
 512   template<typename _Pair>
 513     struct _Select2nd
 514     : public unary_function<_Pair, typename _Pair::second_type>
 515     {
 516       typename _Pair::second_type&
 517       operator()(_Pair& __x) const
 518       { return __x.second; }
 519
 520       const typename _Pair::second_type&
 521       operator()(const _Pair& __x) const
 522       { return __x.second; }
 523     };
 524
 525   // 20.3.8 adaptors pointers members
 526   /** @defgroup memory_adaptors Adaptors for pointers to members
 527    * @ingroup functors
 528    *
 529    *  There are a total of 8 = 2^3 function objects in this family.
 530    *   (1) Member functions taking no arguments vs member functions taking
 531    *        one argument.
 532    *   (2) Call through pointer vs call through reference.
 533    *   (3) Const vs non-const member function.
 534    *
 535    *  All of this complexity is in the function objects themselves.  You can
 536    *   ignore it by using the helper function mem_fun and mem_fun_ref,
 537    *   which create whichever type of adaptor is appropriate.
 538    *
 539    *  @{
 540    */
 541   /// One of the @link memory_adaptors adaptors for member
 542   /// pointers@endlink.
 543   template<typename _Ret, typename _Tp>
 544     class mem_fun_t : public unary_function<_Tp*, _Ret>
 545     {
 546     public:
 547       explicit
 548       mem_fun_t(_Ret (_Tp::*__pf)())
 549       : _M_f(__pf) { }
 550
 551       _Ret
 552       operator()(_Tp* __p) const
 553       { return (__p->*_M_f)(); }
 554
 555     private:
 556       _Ret (_Tp::*_M_f)();
 557     };
 558
 559   /// One of the @link memory_adaptors adaptors for member
 560   /// pointers@endlink.
 561   template<typename _Ret, typename _Tp>
 562     class const_mem_fun_t : public unary_function<const _Tp*, _Ret>
 563     {
 564     public:
 565       explicit
 566       const_mem_fun_t(_Ret (_Tp::*__pf)() const)
 567       : _M_f(__pf) { }
 568
 569       _Ret
 570       operator()(const _Tp* __p) const
 571       { return (__p->*_M_f)(); }
 572
 573     private:
 574       _Ret (_Tp::*_M_f)() const;
 575     };
 576
 577   /// One of the @link memory_adaptors adaptors for member
 578   /// pointers@endlink.
 579   template<typename _Ret, typename _Tp>
 580     class mem_fun_ref_t : public unary_function<_Tp, _Ret>
 581     {
 582     public:
 583       explicit
 584       mem_fun_ref_t(_Ret (_Tp::*__pf)())
 585       : _M_f(__pf) { }
 586
 587       _Ret
 588       operator()(_Tp& __r) const
 589       { return (__r.*_M_f)(); }
 590
 591     private:
 592       _Ret (_Tp::*_M_f)();
 593   };
 594
 595   /// One of the @link memory_adaptors adaptors for member
 596   /// pointers@endlink.
 597   template<typename _Ret, typename _Tp>
 598     class const_mem_fun_ref_t : public unary_function<_Tp, _Ret>
 599     {
 600     public:
 601       explicit
 602       const_mem_fun_ref_t(_Ret (_Tp::*__pf)() const)
 603       : _M_f(__pf) { }
 604
 605       _Ret
 606       operator()(const _Tp& __r) const
 607       { return (__r.*_M_f)(); }
 608
 609     private:
 610       _Ret (_Tp::*_M_f)() const;
 611     };
 612
 613   /// One of the @link memory_adaptors adaptors for member
 614   /// pointers@endlink.
 615   template<typename _Ret, typename _Tp, typename _Arg>
 616     class mem_fun1_t : public binary_function<_Tp*, _Arg, _Ret>
 617     {
 618     public:
 619       explicit
 620       mem_fun1_t(_Ret (_Tp::*__pf)(_Arg))
 621       : _M_f(__pf) { }
 622
 623       _Ret
 624       operator()(_Tp* __p, _Arg __x) const
 625       { return (__p->*_M_f)(__x); }
 626
 627     private:
 628       _Ret (_Tp::*_M_f)(_Arg);
 629     };
 630
 631   /// One of the @link memory_adaptors adaptors for member
 632   /// pointers@endlink.
 633   template<typename _Ret, typename _Tp, typename _Arg>
 634     class const_mem_fun1_t : public binary_function<const _Tp*, _Arg, _Ret>
 635     {
 636     public:
 637       explicit
 638       const_mem_fun1_t(_Ret (_Tp::*__pf)(_Arg) const)
 639       : _M_f(__pf) { }
 640
 641       _Ret
 642       operator()(const _Tp* __p, _Arg __x) const
 643       { return (__p->*_M_f)(__x); }
 644
 645     private:
 646       _Ret (_Tp::*_M_f)(_Arg) const;
 647     };
 648
 649   /// One of the @link memory_adaptors adaptors for member
 650   /// pointers@endlink.
 651   template<typename _Ret, typename _Tp, typename _Arg>
 652     class mem_fun1_ref_t : public binary_function<_Tp, _Arg, _Ret>
 653     {
 654     public:
 655       explicit
 656       mem_fun1_ref_t(_Ret (_Tp::*__pf)(_Arg))
 657       : _M_f(__pf) { }
 658
 659       _Ret
 660       operator()(_Tp& __r, _Arg __x) const
 661       { return (__r.*_M_f)(__x); }
 662
 663     private:
 664       _Ret (_Tp::*_M_f)(_Arg);
 665     };
 666
 667   /// One of the @link memory_adaptors adaptors for member
 668   /// pointers@endlink.
 669   template<typename _Ret, typename _Tp, typename _Arg>
 670     class const_mem_fun1_ref_t : public binary_function<_Tp, _Arg, _Ret>
 671     {
 672     public:
 673       explicit
 674       const_mem_fun1_ref_t(_Ret (_Tp::*__pf)(_Arg) const)
 675       : _M_f(__pf) { }
 676
 677       _Ret
 678       operator()(const _Tp& __r, _Arg __x) const
 679       { return (__r.*_M_f)(__x); }
 680
 681     private:
 682       _Ret (_Tp::*_M_f)(_Arg) const;
 683     };
 684
 685   // Mem_fun adaptor helper functions.  There are only two:
 686   // mem_fun and mem_fun_ref.
 687   template<typename _Ret, typename _Tp>
 688     inline mem_fun_t<_Ret, _Tp>
 689     mem_fun(_Ret (_Tp::*__f)())
 690     { return mem_fun_t<_Ret, _Tp>(__f); }
 691
 692   template<typename _Ret, typename _Tp>
 693     inline const_mem_fun_t<_Ret, _Tp>
 694     mem_fun(_Ret (_Tp::*__f)() const)
 695     { return const_mem_fun_t<_Ret, _Tp>(__f); }
 696
 697   template<typename _Ret, typename _Tp>
 698     inline mem_fun_ref_t<_Ret, _Tp>
 699     mem_fun_ref(_Ret (_Tp::*__f)())
 700     { return mem_fun_ref_t<_Ret, _Tp>(__f); }
 701
 702   template<typename _Ret, typename _Tp>
 703     inline const_mem_fun_ref_t<_Ret, _Tp>
 704     mem_fun_ref(_Ret (_Tp::*__f)() const)
 705     { return const_mem_fun_ref_t<_Ret, _Tp>(__f); }
 706
 707   template<typename _Ret, typename _Tp, typename _Arg>
 708     inline mem_fun1_t<_Ret, _Tp, _Arg>
 709     mem_fun(_Ret (_Tp::*__f)(_Arg))
 710     { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
 711
 712   template<typename _Ret, typename _Tp, typename _Arg>
 713     inline const_mem_fun1_t<_Ret, _Tp, _Arg>
 714     mem_fun(_Ret (_Tp::*__f)(_Arg) const)
 715     { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
 716
 717   template<typename _Ret, typename _Tp, typename _Arg>
 718     inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
 719     mem_fun_ref(_Ret (_Tp::*__f)(_Arg))
 720     { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
 721
 722   template<typename _Ret, typename _Tp, typename _Arg>
 723     inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
 724     mem_fun_ref(_Ret (_Tp::*__f)(_Arg) const)
 725     { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
 726
 727   /** @}  */
 728
 729 _GLIBCXX_END_NAMESPACE_VERSION
 730 } // namespace
 731
 732 #if (__cplusplus < 201103L) || _GLIBCXX_USE_DEPRECATED
 733 # include <backward/binders.h>
 734 #endif
 735
 736 #endif /* _STL_FUNCTION_H */