libstdc++-v3/include/ext/functional

   1 // Functional extensions -*- C++ -*-
   2
   3 // Copyright (C) 2002-2024 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 <bits/requires_hosted.h> // GNU extensions are currently omitted
  62
  63 #include <functional>
  64
  65 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  66 {
  67 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  68
  69 #pragma GCC diagnostic push
  70 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
  71
  72   /** The @c identity_element functions are not part of the C++
  73    *  standard; SGI provided them as an extension.  Its argument is an
  74    *  operation, and its return value is the identity element for that
  75    *  operation.  It is overloaded for addition and multiplication,
  76    *  and you can overload it for your own nefarious operations.
  77    *
  78    *  @addtogroup SGIextensions
  79    *  @{
  80    */
  81   /// An \link SGIextensions SGI extension \endlink.
  82   template <class _Tp>
  83     inline _Tp
  84     identity_element(std::plus<_Tp>)
  85     { return _Tp(0); }
  86
  87   /// An \link SGIextensions SGI extension \endlink.
  88   template <class _Tp>
  89     inline _Tp
  90     identity_element(std::multiplies<_Tp>)
  91     { return _Tp(1); }
  92   /** @}  */
  93
  94   /** As an extension to the binders, SGI provided composition functors and
  95    *  wrapper functions to aid in their creation.  The @c unary_compose
  96    *  functor is constructed from two functions/functors, @c f and @c g.
  97    *  Calling @c operator() with a single argument @c x returns @c f(g(x)).
  98    *  The function @c compose1 takes the two functions and constructs a
  99    *  @c unary_compose variable for you.
 100    *
 101    *  @c binary_compose is constructed from three functors, @c f, @c g1,
 102    *  and @c g2.  Its @c operator() returns @c f(g1(x),g2(x)).  The function
 103    *  compose2 takes f, g1, and g2, and constructs the @c binary_compose
 104    *  instance for you.  For example, if @c f returns an int, then
 105    *  \code
 106    *  int answer = (compose2(f,g1,g2))(x);
 107    *  \endcode
 108    *  is equivalent to
 109    *  \code
 110    *  int temp1 = g1(x);
 111    *  int temp2 = g2(x);
 112    *  int answer = f(temp1,temp2);
 113    *  \endcode
 114    *  But the first form is more compact, and can be passed around as a
 115    *  functor to other algorithms.
 116    *
 117    *  @addtogroup SGIextensions
 118    *  @{
 119    */
 120   /// An \link SGIextensions SGI extension \endlink.
 121   template <class _Operation1, class _Operation2>
 122     class unary_compose
 123     : public std::unary_function<typename _Operation2::argument_type,
 124                                  typename _Operation1::result_type>
 125     {
 126     protected:
 127       _Operation1 _M_fn1;
 128       _Operation2 _M_fn2;
 129
 130     public:
 131       unary_compose(const _Operation1& __x, const _Operation2& __y)
 132       : _M_fn1(__x), _M_fn2(__y) {}
 133
 134       typename _Operation1::result_type
 135       operator()(const typename _Operation2::argument_type& __x) const
 136       { return _M_fn1(_M_fn2(__x)); }
 137     };
 138
 139   /// An \link SGIextensions SGI extension \endlink.
 140   template <class _Operation1, class _Operation2>
 141     inline unary_compose<_Operation1, _Operation2>
 142     compose1(const _Operation1& __fn1, const _Operation2& __fn2)
 143     { return unary_compose<_Operation1,_Operation2>(__fn1, __fn2); }
 144
 145   /// An \link SGIextensions SGI extension \endlink.
 146   template <class _Operation1, class _Operation2, class _Operation3>
 147     class binary_compose
 148     : public std::unary_function<typename _Operation2::argument_type,
 149                                  typename _Operation1::result_type>
 150     {
 151     protected:
 152       _Operation1 _M_fn1;
 153       _Operation2 _M_fn2;
 154       _Operation3 _M_fn3;
 155
 156     public:
 157       binary_compose(const _Operation1& __x, const _Operation2& __y,
 158                      const _Operation3& __z)
 159       : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }
 160
 161       typename _Operation1::result_type
 162       operator()(const typename _Operation2::argument_type& __x) const
 163       { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }
 164     };
 165
 166   /// An \link SGIextensions SGI extension \endlink.
 167   template <class _Operation1, class _Operation2, class _Operation3>
 168     inline binary_compose<_Operation1, _Operation2, _Operation3>
 169     compose2(const _Operation1& __fn1, const _Operation2& __fn2,
 170              const _Operation3& __fn3)
 171     { return binary_compose<_Operation1, _Operation2, _Operation3>
 172         (__fn1, __fn2, __fn3); }
 173   /** @}  */
 174
 175   /** As an extension, SGI provided a functor called @c identity.  When a
 176    *  functor is required but no operations are desired, this can be used as a
 177    *  pass-through.  Its @c operator() returns its argument unchanged.
 178    *
 179    *  @addtogroup SGIextensions
 180    */
 181   template <class _Tp>
 182     struct identity
 183     : public std::_Identity<_Tp> {};
 184
 185   /** @c select1st and @c select2nd are extensions provided by SGI.  Their
 186    *  @c operator()s
 187    *  take a @c std::pair as an argument, and return either the first member
 188    *  or the second member, respectively.  They can be used (especially with
 189    *  the composition functors) to @a strip data from a sequence before
 190    *  performing the remainder of an algorithm.
 191    *
 192    *  @addtogroup SGIextensions
 193    *  @{
 194    */
 195   /// An \link SGIextensions SGI extension \endlink.
 196   template <class _Pair>
 197     struct select1st
 198     : public std::_Select1st<_Pair> {};
 199
 200   /// An \link SGIextensions SGI extension \endlink.
 201   template <class _Pair>
 202     struct select2nd
 203     : public std::_Select2nd<_Pair> {};
 204
 205   /** @}  */
 206
 207   // extension documented next
 208   template <class _Arg1, class _Arg2>
 209     struct _Project1st : public std::binary_function<_Arg1, _Arg2, _Arg1>
 210     {
 211       _Arg1
 212       operator()(const _Arg1& __x, const _Arg2&) const
 213       { return __x; }
 214     };
 215
 216   template <class _Arg1, class _Arg2>
 217     struct _Project2nd : public std::binary_function<_Arg1, _Arg2, _Arg2>
 218     {
 219       _Arg2
 220       operator()(const _Arg1&, const _Arg2& __y) const
 221       { return __y; }
 222     };
 223
 224   /** The @c operator() of the @c project1st functor takes two arbitrary
 225    *  arguments and returns the first one, while @c project2nd returns the
 226    *  second one.  They are extensions provided by SGI.
 227    *
 228    *  @addtogroup SGIextensions
 229    *  @{
 230    */
 231
 232   /// An \link SGIextensions SGI extension \endlink.
 233   template <class _Arg1, class _Arg2>
 234     struct project1st : public _Project1st<_Arg1, _Arg2> {};
 235
 236   /// An \link SGIextensions SGI extension \endlink.
 237   template <class _Arg1, class _Arg2>
 238     struct project2nd : public _Project2nd<_Arg1, _Arg2> {};
 239   /** @}  */
 240
 241   // extension documented next
 242   template <class _Result>
 243     struct _Constant_void_fun
 244     {
 245       typedef _Result result_type;
 246       result_type _M_val;
 247
 248       _Constant_void_fun(const result_type& __v) : _M_val(__v) {}
 249
 250       const result_type&
 251       operator()() const
 252       { return _M_val; }
 253     };
 254
 255   template <class _Result, class _Argument>
 256     struct _Constant_unary_fun
 257     {
 258       typedef _Argument argument_type;
 259       typedef  _Result  result_type;
 260       result_type _M_val;
 261
 262       _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}
 263
 264       const result_type&
 265       operator()(const _Argument&) const
 266       { return _M_val; }
 267     };
 268
 269   template <class _Result, class _Arg1, class _Arg2>
 270     struct _Constant_binary_fun
 271     {
 272       typedef  _Arg1   first_argument_type;
 273       typedef  _Arg2   second_argument_type;
 274       typedef  _Result result_type;
 275       _Result _M_val;
 276
 277       _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}
 278
 279       const result_type&
 280       operator()(const _Arg1&, const _Arg2&) const
 281       { return _M_val; }
 282     };
 283
 284   /** These three functors are each constructed from a single arbitrary
 285    *  variable/value.  Later, their @c operator()s completely ignore any
 286    *  arguments passed, and return the stored value.
 287    *  - @c constant_void_fun's @c operator() takes no arguments
 288    *  - @c constant_unary_fun's @c operator() takes one argument (ignored)
 289    *  - @c constant_binary_fun's @c operator() takes two arguments (ignored)
 290    *
 291    *  The helper creator functions @c constant0, @c constant1, and
 292    *  @c constant2 each take a @a result argument and construct variables of
 293    *  the appropriate functor type.
 294    *
 295    *  @addtogroup SGIextensions
 296    *  @{
 297    */
 298   /// An \link SGIextensions SGI extension \endlink.
 299   template <class _Result>
 300     struct constant_void_fun
 301     : public _Constant_void_fun<_Result>
 302     {
 303       constant_void_fun(const _Result& __v)
 304       : _Constant_void_fun<_Result>(__v) {}
 305     };
 306
 307   /// An \link SGIextensions SGI extension \endlink.
 308   template <class _Result, class _Argument = _Result>
 309     struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>
 310     {
 311       constant_unary_fun(const _Result& __v)
 312       : _Constant_unary_fun<_Result, _Argument>(__v) {}
 313     };
 314
 315   /// An \link SGIextensions SGI extension \endlink.
 316   template <class _Result, class _Arg1 = _Result, class _Arg2 = _Arg1>
 317     struct constant_binary_fun
 318     : public _Constant_binary_fun<_Result, _Arg1, _Arg2>
 319     {
 320       constant_binary_fun(const _Result& __v)
 321       : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}
 322     };
 323
 324   /// An \link SGIextensions SGI extension \endlink.
 325   template <class _Result>
 326     inline constant_void_fun<_Result>
 327     constant0(const _Result& __val)
 328     { return constant_void_fun<_Result>(__val); }
 329
 330   /// An \link SGIextensions SGI extension \endlink.
 331   template <class _Result>
 332     inline constant_unary_fun<_Result, _Result>
 333     constant1(const _Result& __val)
 334     { return constant_unary_fun<_Result, _Result>(__val); }
 335
 336   /// An \link SGIextensions SGI extension \endlink.
 337   template <class _Result>
 338     inline constant_binary_fun<_Result,_Result,_Result>
 339     constant2(const _Result& __val)
 340     { return constant_binary_fun<_Result, _Result, _Result>(__val); }
 341   /** @}  */
 342
 343   /** The @c subtractive_rng class is documented on
 344    *  <a href="http://www.sgi.com/tech/stl/">SGI's site</a>.
 345    *  Note that this code assumes that @c int is 32 bits.
 346    *
 347    *  @ingroup SGIextensions
 348    */
 349   class subtractive_rng
 350   : public std::unary_function<unsigned int, unsigned int>
 351   {
 352   private:
 353     unsigned int _M_table[55];
 354     std::size_t _M_index1;
 355     std::size_t _M_index2;
 356
 357   public:
 358     /// Returns a number less than the argument.
 359     unsigned int
 360     operator()(unsigned int __limit)
 361     {
 362       _M_index1 = (_M_index1 + 1) % 55;
 363       _M_index2 = (_M_index2 + 1) % 55;
 364       _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];
 365       return _M_table[_M_index1] % __limit;
 366     }
 367
 368     void
 369     _M_initialize(unsigned int __seed)
 370     {
 371       unsigned int __k = 1;
 372       _M_table[54] = __seed;
 373       std::size_t __i;
 374       for (__i = 0; __i < 54; __i++)
 375         {
 376           std::size_t __ii = (21 * (__i + 1) % 55) - 1;
 377           _M_table[__ii] = __k;
 378           __k = __seed - __k;
 379           __seed = _M_table[__ii];
 380         }
 381       for (int __loop = 0; __loop < 4; __loop++)
 382         {
 383           for (__i = 0; __i < 55; __i++)
 384             _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];
 385         }
 386       _M_index1 = 0;
 387       _M_index2 = 31;
 388     }
 389
 390     /// Ctor allowing you to initialize the seed.
 391     subtractive_rng(unsigned int __seed)
 392     { _M_initialize(__seed); }
 393
 394     /// Default ctor; initializes its state with some number you don't see.
 395     subtractive_rng()
 396     { _M_initialize(161803398u); }
 397   };
 398
 399   // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,
 400   // provided for backward compatibility, they are no longer part of
 401   // the C++ standard.
 402
 403   template <class _Ret, class _Tp, class _Arg>
 404     inline std::mem_fun1_t<_Ret, _Tp, _Arg>
 405     mem_fun1(_Ret (_Tp::*__f)(_Arg))
 406     { return std::mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
 407
 408   template <class _Ret, class _Tp, class _Arg>
 409     inline std::const_mem_fun1_t<_Ret, _Tp, _Arg>
 410     mem_fun1(_Ret (_Tp::*__f)(_Arg) const)
 411     { return std::const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
 412
 413   template <class _Ret, class _Tp, class _Arg>
 414     inline std::mem_fun1_ref_t<_Ret, _Tp, _Arg>
 415     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))
 416     { return std::mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
 417
 418   template <class _Ret, class _Tp, class _Arg>
 419     inline std::const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
 420     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)
 421     { return std::const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
 422
 423 #pragma GCC diagnostic pop
 424
 425 _GLIBCXX_END_NAMESPACE_VERSION
 426 } // namespace
 427
 428 #endif
 429