libstdc++-v3/include/ext/functional

   1 // Functional extensions -*- C++ -*-
   2
   3 // Copyright (C) 2002-2016 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 <functional>
  62
  63 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
  64 {
  65 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  66
  67   using std::size_t;
  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;
  74
  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.
  80    *
  81    *  @addtogroup SGIextensions
  82    *  @{
  83    */
  84   /// An \link SGIextensions SGI extension \endlink.
  85   template <class _Tp>
  86     inline _Tp
  87     identity_element(std::plus<_Tp>)
  88     { return _Tp(0); }
  89
  90   /// An \link SGIextensions SGI extension \endlink.
  91   template <class _Tp>
  92     inline _Tp
  93     identity_element(std::multiplies<_Tp>)
  94     { return _Tp(1); }
  95   /** @}  */
  96
  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.
 103    *
 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
 108    *  \code
 109    *  int answer = (compose2(f,g1,g2))(x);
 110    *  \endcode
 111    *  is equivalent to
 112    *  \code
 113    *  int temp1 = g1(x);
 114    *  int temp2 = g2(x);
 115    *  int answer = f(temp1,temp2);
 116    *  \endcode
 117    *  But the first form is more compact, and can be passed around as a
 118    *  functor to other algorithms.
 119    *
 120    *  @addtogroup SGIextensions
 121    *  @{
 122    */
 123   /// An \link SGIextensions SGI extension \endlink.
 124   template <class _Operation1, class _Operation2>
 125     class unary_compose
 126     : public unary_function<typename _Operation2::argument_type,
 127                             typename _Operation1::result_type>
 128     {
 129     protected:
 130       _Operation1 _M_fn1;
 131       _Operation2 _M_fn2;
 132
 133     public:
 134       unary_compose(const _Operation1& __x, const _Operation2& __y)
 135       : _M_fn1(__x), _M_fn2(__y) {}
 136
 137       typename _Operation1::result_type
 138       operator()(const typename _Operation2::argument_type& __x) const
 139       { return _M_fn1(_M_fn2(__x)); }
 140     };
 141
 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); }
 147
 148   /// An \link SGIextensions SGI extension \endlink.
 149   template <class _Operation1, class _Operation2, class _Operation3>
 150     class binary_compose
 151     : public unary_function<typename _Operation2::argument_type,
 152                             typename _Operation1::result_type>
 153     {
 154     protected:
 155       _Operation1 _M_fn1;
 156       _Operation2 _M_fn2;
 157       _Operation3 _M_fn3;
 158
 159     public:
 160       binary_compose(const _Operation1& __x, const _Operation2& __y,
 161                      const _Operation3& __z)
 162       : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }
 163
 164       typename _Operation1::result_type
 165       operator()(const typename _Operation2::argument_type& __x) const
 166       { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }
 167     };
 168
 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); }
 176   /** @}  */
 177
 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.
 181    *
 182    *  @addtogroup SGIextensions
 183    */
 184   template <class _Tp>
 185     struct identity
 186     : public std::_Identity<_Tp> {};
 187
 188   /** @c select1st and @c select2nd are extensions provided by SGI.  Their
 189    *  @c operator()s
 190    *  take a @c std::pair as an argument, and return either the first member
 191    *  or the second member, respectively.  They can be used (especially with
 192    *  the composition functors) to @a strip data from a sequence before
 193    *  performing the remainder of an algorithm.
 194    *
 195    *  @addtogroup SGIextensions
 196    *  @{
 197    */
 198   /// An \link SGIextensions SGI extension \endlink.
 199   template <class _Pair>
 200     struct select1st
 201     : public std::_Select1st<_Pair> {};
 202
 203   /// An \link SGIextensions SGI extension \endlink.
 204   template <class _Pair>
 205     struct select2nd
 206     : public std::_Select2nd<_Pair> {};
 207
 208   /** @}  */
 209
 210   // extension documented next
 211   template <class _Arg1, class _Arg2>
 212     struct _Project1st : public binary_function<_Arg1, _Arg2, _Arg1>
 213     {
 214       _Arg1
 215       operator()(const _Arg1& __x, const _Arg2&) const
 216       { return __x; }
 217     };
 218
 219   template <class _Arg1, class _Arg2>
 220     struct _Project2nd : public binary_function<_Arg1, _Arg2, _Arg2>
 221     {
 222       _Arg2
 223       operator()(const _Arg1&, const _Arg2& __y) const
 224       { return __y; }
 225     };
 226
 227   /** The @c operator() of the @c project1st functor takes two arbitrary
 228    *  arguments and returns the first one, while @c project2nd returns the
 229    *  second one.  They are extensions provided by SGI.
 230    *
 231    *  @addtogroup SGIextensions
 232    *  @{
 233    */
 234
 235   /// An \link SGIextensions SGI extension \endlink.
 236   template <class _Arg1, class _Arg2>
 237     struct project1st : public _Project1st<_Arg1, _Arg2> {};
 238
 239   /// An \link SGIextensions SGI extension \endlink.
 240   template <class _Arg1, class _Arg2>
 241     struct project2nd : public _Project2nd<_Arg1, _Arg2> {};
 242   /** @}  */
 243
 244   // extension documented next
 245   template <class _Result>
 246     struct _Constant_void_fun
 247     {
 248       typedef _Result result_type;
 249       result_type _M_val;
 250
 251       _Constant_void_fun(const result_type& __v) : _M_val(__v) {}
 252
 253       const result_type&
 254       operator()() const
 255       { return _M_val; }
 256     };
 257
 258   template <class _Result, class _Argument>
 259     struct _Constant_unary_fun
 260     {
 261       typedef _Argument argument_type;
 262       typedef  _Result  result_type;
 263       result_type _M_val;
 264
 265       _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}
 266
 267       const result_type&
 268       operator()(const _Argument&) const
 269       { return _M_val; }
 270     };
 271
 272   template <class _Result, class _Arg1, class _Arg2>
 273     struct _Constant_binary_fun
 274     {
 275       typedef  _Arg1   first_argument_type;
 276       typedef  _Arg2   second_argument_type;
 277       typedef  _Result result_type;
 278       _Result _M_val;
 279
 280       _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}
 281
 282       const result_type&
 283       operator()(const _Arg1&, const _Arg2&) const
 284       { return _M_val; }
 285     };
 286
 287   /** These three functors are each constructed from a single arbitrary
 288    *  variable/value.  Later, their @c operator()s completely ignore any
 289    *  arguments passed, and return the stored value.
 290    *  - @c constant_void_fun's @c operator() takes no arguments
 291    *  - @c constant_unary_fun's @c operator() takes one argument (ignored)
 292    *  - @c constant_binary_fun's @c operator() takes two arguments (ignored)
 293    *
 294    *  The helper creator functions @c constant0, @c constant1, and
 295    *  @c constant2 each take a @a result argument and construct variables of
 296    *  the appropriate functor type.
 297    *
 298    *  @addtogroup SGIextensions
 299    *  @{
 300    */
 301   /// An \link SGIextensions SGI extension \endlink.
 302   template <class _Result>
 303     struct constant_void_fun
 304     : public _Constant_void_fun<_Result>
 305     {
 306       constant_void_fun(const _Result& __v)
 307       : _Constant_void_fun<_Result>(__v) {}
 308     };
 309
 310   /// An \link SGIextensions SGI extension \endlink.
 311   template <class _Result, class _Argument = _Result>
 312     struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>
 313     {
 314       constant_unary_fun(const _Result& __v)
 315       : _Constant_unary_fun<_Result, _Argument>(__v) {}
 316     };
 317
 318   /// An \link SGIextensions SGI extension \endlink.
 319   template <class _Result, class _Arg1 = _Result, class _Arg2 = _Arg1>
 320     struct constant_binary_fun
 321     : public _Constant_binary_fun<_Result, _Arg1, _Arg2>
 322     {
 323       constant_binary_fun(const _Result& __v)
 324       : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}
 325     };
 326
 327   /// An \link SGIextensions SGI extension \endlink.
 328   template <class _Result>
 329     inline constant_void_fun<_Result>
 330     constant0(const _Result& __val)
 331     { return constant_void_fun<_Result>(__val); }
 332
 333   /// An \link SGIextensions SGI extension \endlink.
 334   template <class _Result>
 335     inline constant_unary_fun<_Result, _Result>
 336     constant1(const _Result& __val)
 337     { return constant_unary_fun<_Result, _Result>(__val); }
 338
 339   /// An \link SGIextensions SGI extension \endlink.
 340   template <class _Result>
 341     inline constant_binary_fun<_Result,_Result,_Result>
 342     constant2(const _Result& __val)
 343     { return constant_binary_fun<_Result, _Result, _Result>(__val); }
 344   /** @}  */
 345
 346   /** The @c subtractive_rng class is documented on
 347    *  <a href="http://www.sgi.com/tech/stl/">SGI's site</a>.
 348    *  Note that this code assumes that @c int is 32 bits.
 349    *
 350    *  @ingroup SGIextensions
 351    */
 352   class subtractive_rng
 353   : public unary_function<unsigned int, unsigned int>
 354   {
 355   private:
 356     unsigned int _M_table[55];
 357     size_t _M_index1;
 358     size_t _M_index2;
 359
 360   public:
 361     /// Returns a number less than the argument.
 362     unsigned int
 363     operator()(unsigned int __limit)
 364     {
 365       _M_index1 = (_M_index1 + 1) % 55;
 366       _M_index2 = (_M_index2 + 1) % 55;
 367       _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];
 368       return _M_table[_M_index1] % __limit;
 369     }
 370
 371     void
 372     _M_initialize(unsigned int __seed)
 373     {
 374       unsigned int __k = 1;
 375       _M_table[54] = __seed;
 376       size_t __i;
 377       for (__i = 0; __i < 54; __i++)
 378         {
 379           size_t __ii = (21 * (__i + 1) % 55) - 1;
 380           _M_table[__ii] = __k;
 381           __k = __seed - __k;
 382           __seed = _M_table[__ii];
 383         }
 384       for (int __loop = 0; __loop < 4; __loop++)
 385         {
 386           for (__i = 0; __i < 55; __i++)
 387             _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];
 388         }
 389       _M_index1 = 0;
 390       _M_index2 = 31;
 391     }
 392
 393     /// Ctor allowing you to initialize the seed.
 394     subtractive_rng(unsigned int __seed)
 395     { _M_initialize(__seed); }
 396
 397     /// Default ctor; initializes its state with some number you don't see.
 398     subtractive_rng()
 399     { _M_initialize(161803398u); }
 400   };
 401
 402   // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,
 403   // provided for backward compatibility, they are no longer part of
 404   // the C++ standard.
 405
 406   template <class _Ret, class _Tp, class _Arg>
 407     inline mem_fun1_t<_Ret, _Tp, _Arg>
 408     mem_fun1(_Ret (_Tp::*__f)(_Arg))
 409     { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
 410
 411   template <class _Ret, class _Tp, class _Arg>
 412     inline const_mem_fun1_t<_Ret, _Tp, _Arg>
 413     mem_fun1(_Ret (_Tp::*__f)(_Arg) const)
 414     { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
 415
 416   template <class _Ret, class _Tp, class _Arg>
 417     inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
 418     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))
 419     { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
 420
 421   template <class _Ret, class _Tp, class _Arg>
 422     inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
 423     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)
 424     { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
 425
 426 _GLIBCXX_END_NAMESPACE_VERSION
 427 } // namespace
 428
 429 #endif
 430