libstdc++-v3/include/ext/functional

   1 // Functional extensions -*- C++ -*-
   2
   3 // Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007
   4 // Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 2, or (at your option)
  10 // any later version.
  11
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING.  If not, write to the Free
  19 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  20 // USA.
  21
  22 // As a special exception, you may use this file as part of a free software
  23 // library without restriction.  Specifically, if other files instantiate
  24 // templates or use macros or inline functions from this file, or you compile
  25 // this file and link it with other files to produce an executable, this
  26 // file does not by itself cause the resulting executable to be covered by
  27 // the GNU General Public License.  This exception does not however
  28 // invalidate any other reasons why the executable file might be covered by
  29 // the GNU General Public License.
  30
  31 /*
  32  *
  33  * Copyright (c) 1994
  34  * Hewlett-Packard Company
  35  *
  36  * Permission to use, copy, modify, distribute and sell this software
  37  * and its documentation for any purpose is hereby granted without fee,
  38  * provided that the above copyright notice appear in all copies and
  39  * that both that copyright notice and this permission notice appear
  40  * in supporting documentation.  Hewlett-Packard Company makes no
  41  * representations about the suitability of this software for any
  42  * purpose.  It is provided "as is" without express or implied warranty.
  43  *
  44  *
  45  * Copyright (c) 1996
  46  * Silicon Graphics Computer Systems, Inc.
  47  *
  48  * Permission to use, copy, modify, distribute and sell this software
  49  * and its documentation for any purpose is hereby granted without fee,
  50  * provided that the above copyright notice appear in all copies and
  51  * that both that copyright notice and this permission notice appear
  52  * in supporting documentation.  Silicon Graphics makes no
  53  * representations about the suitability of this software for any
  54  * purpose.  It is provided "as is" without express or implied warranty.
  55  */
  56
  57 /** @file ext/functional
  58  *  This file is a GNU extension to the Standard C++ Library (possibly
  59  *  containing extensions from the HP/SGI STL subset).
  60  */
  61
  62 #ifndef _EXT_FUNCTIONAL
  63 #define _EXT_FUNCTIONAL 1
  64
  65 #pragma GCC system_header
  66
  67 #include <functional>
  68 #include <cstddef>
  69
  70 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
  71
  72   using std::size_t;
  73   using std::unary_function;
  74   using std::binary_function;
  75   using std::mem_fun1_t;
  76   using std::const_mem_fun1_t;
  77   using std::mem_fun1_ref_t;
  78   using std::const_mem_fun1_ref_t;
  79
  80   /** The @c identity_element functions are not part of the C++
  81    *  standard; SGI provided them as an extension.  Its argument is an
  82    *  operation, and its return value is the identity element for that
  83    *  operation.  It is overloaded for addition and multiplication,
  84    *  and you can overload it for your own nefarious operations.
  85    *
  86    *  @addtogroup SGIextensions
  87    *  @{
  88    */
  89   /// An \link SGIextensions SGI extension \endlink.
  90   template <class _Tp>
  91     inline _Tp
  92     identity_element(std::plus<_Tp>)
  93     { return _Tp(0); }
  94
  95   /// An \link SGIextensions SGI extension \endlink.
  96   template <class _Tp>
  97     inline _Tp
  98     identity_element(std::multiplies<_Tp>)
  99     { return _Tp(1); }
 100   /** @}  */
 101
 102   /** As an extension to the binders, SGI provided composition functors and
 103    *  wrapper functions to aid in their creation.  The @c unary_compose
 104    *  functor is constructed from two functions/functors, @c f and @c g.
 105    *  Calling @c operator() with a single argument @c x returns @c f(g(x)).
 106    *  The function @c compose1 takes the two functions and constructs a
 107    *  @c unary_compose variable for you.
 108    *
 109    *  @c binary_compose is constructed from three functors, @c f, @c g1,
 110    *  and @c g2.  Its @c operator() returns @c f(g1(x),g2(x)).  The function
 111    *  @compose2 takes f, g1, and g2, and constructs the @c binary_compose
 112    *  instance for you.  For example, if @c f returns an int, then
 113    *  \code
 114    *  int answer = (compose2(f,g1,g2))(x);
 115    *  \endcode
 116    *  is equivalent to
 117    *  \code
 118    *  int temp1 = g1(x);
 119    *  int temp2 = g2(x);
 120    *  int answer = f(temp1,temp2);
 121    *  \endcode
 122    *  But the first form is more compact, and can be passed around as a
 123    *  functor to other algorithms.
 124    *
 125    *  @addtogroup SGIextensions
 126    *  @{
 127    */
 128   /// An \link SGIextensions SGI extension \endlink.
 129   template <class _Operation1, class _Operation2>
 130     class unary_compose
 131     : public unary_function<typename _Operation2::argument_type,
 132                             typename _Operation1::result_type>
 133     {
 134     protected:
 135       _Operation1 _M_fn1;
 136       _Operation2 _M_fn2;
 137
 138     public:
 139       unary_compose(const _Operation1& __x, const _Operation2& __y)
 140       : _M_fn1(__x), _M_fn2(__y) {}
 141
 142       typename _Operation1::result_type
 143       operator()(const typename _Operation2::argument_type& __x) const
 144       { return _M_fn1(_M_fn2(__x)); }
 145     };
 146
 147   /// An \link SGIextensions SGI extension \endlink.
 148   template <class _Operation1, class _Operation2>
 149     inline unary_compose<_Operation1, _Operation2>
 150     compose1(const _Operation1& __fn1, const _Operation2& __fn2)
 151     { return unary_compose<_Operation1,_Operation2>(__fn1, __fn2); }
 152
 153   /// An \link SGIextensions SGI extension \endlink.
 154   template <class _Operation1, class _Operation2, class _Operation3>
 155     class binary_compose
 156     : public unary_function<typename _Operation2::argument_type,
 157                             typename _Operation1::result_type>
 158     {
 159     protected:
 160       _Operation1 _M_fn1;
 161       _Operation2 _M_fn2;
 162       _Operation3 _M_fn3;
 163
 164     public:
 165       binary_compose(const _Operation1& __x, const _Operation2& __y,
 166                      const _Operation3& __z)
 167       : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }
 168
 169       typename _Operation1::result_type
 170       operator()(const typename _Operation2::argument_type& __x) const
 171       { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }
 172     };
 173
 174   /// An \link SGIextensions SGI extension \endlink.
 175   template <class _Operation1, class _Operation2, class _Operation3>
 176     inline binary_compose<_Operation1, _Operation2, _Operation3>
 177     compose2(const _Operation1& __fn1, const _Operation2& __fn2,
 178              const _Operation3& __fn3)
 179     { return binary_compose<_Operation1, _Operation2, _Operation3>
 180         (__fn1, __fn2, __fn3); }
 181   /** @}  */
 182
 183   /** As an extension, SGI provided a functor called @c identity.  When a
 184    *  functor is required but no operations are desired, this can be used as a
 185    *  pass-through.  Its @c operator() returns its argument unchanged.
 186    *
 187    *  @addtogroup SGIextensions
 188    */
 189   template <class _Tp>
 190     struct identity : public std::_Identity<_Tp> {};
 191
 192   /** @c select1st and @c select2nd are extensions provided by SGI.  Their
 193    *  @c operator()s
 194    *  take a @c std::pair as an argument, and return either the first member
 195    *  or the second member, respectively.  They can be used (especially with
 196    *  the composition functors) to "strip" data from a sequence before
 197    *  performing the remainder of an algorithm.
 198    *
 199    *  @addtogroup SGIextensions
 200    *  @{
 201    */
 202   /// An \link SGIextensions SGI extension \endlink.
 203   template <class _Pair>
 204     struct select1st : public std::_Select1st<_Pair> {};
 205
 206   /// An \link SGIextensions SGI extension \endlink.
 207   template <class _Pair>
 208     struct select2nd : public std::_Select2nd<_Pair> {};
 209   /** @}  */
 210
 211   // extension documented next
 212   template <class _Arg1, class _Arg2>
 213     struct _Project1st : public binary_function<_Arg1, _Arg2, _Arg1>
 214     {
 215       _Arg1
 216       operator()(const _Arg1& __x, const _Arg2&) const
 217       { return __x; }
 218     };
 219
 220   template <class _Arg1, class _Arg2>
 221     struct _Project2nd : public binary_function<_Arg1, _Arg2, _Arg2>
 222     {
 223       _Arg2
 224       operator()(const _Arg1&, const _Arg2& __y) const
 225       { return __y; }
 226     };
 227
 228   /** The @c operator() of the @c project1st functor takes two arbitrary
 229    *  arguments and returns the first one, while @c project2nd returns the
 230    *  second one.  They are extensions provided by SGI.
 231    *
 232    *  @addtogroup SGIextensions
 233    *  @{
 234    */
 235
 236   /// An \link SGIextensions SGI extension \endlink.
 237   template <class _Arg1, class _Arg2>
 238     struct project1st : public _Project1st<_Arg1, _Arg2> {};
 239
 240   /// An \link SGIextensions SGI extension \endlink.
 241   template <class _Arg1, class _Arg2>
 242     struct project2nd : public _Project2nd<_Arg1, _Arg2> {};
 243   /** @}  */
 244
 245   // extension documented next
 246   template <class _Result>
 247     struct _Constant_void_fun
 248     {
 249       typedef _Result result_type;
 250       result_type _M_val;
 251
 252       _Constant_void_fun(const result_type& __v) : _M_val(__v) {}
 253
 254       const result_type&
 255       operator()() const
 256       { return _M_val; }
 257     };
 258
 259   template <class _Result, class _Argument>
 260     struct _Constant_unary_fun
 261     {
 262       typedef _Argument argument_type;
 263       typedef  _Result  result_type;
 264       result_type _M_val;
 265
 266       _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}
 267
 268       const result_type&
 269       operator()(const _Argument&) const
 270       { return _M_val; }
 271     };
 272
 273   template <class _Result, class _Arg1, class _Arg2>
 274     struct _Constant_binary_fun
 275     {
 276       typedef  _Arg1   first_argument_type;
 277       typedef  _Arg2   second_argument_type;
 278       typedef  _Result result_type;
 279       _Result _M_val;
 280
 281       _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}
 282
 283       const result_type&
 284       operator()(const _Arg1&, const _Arg2&) const
 285       { return _M_val; }
 286     };
 287
 288   /** These three functors are each constructed from a single arbitrary
 289    *  variable/value.  Later, their @c operator()s completely ignore any
 290    *  arguments passed, and return the stored value.
 291    *  - @c constant_void_fun's @c operator() takes no arguments
 292    *  - @c constant_unary_fun's @c operator() takes one argument (ignored)
 293    *  - @c constant_binary_fun's @c operator() takes two arguments (ignored)
 294    *
 295    *  The helper creator functions @c constant0, @c constant1, and
 296    *  @c constant2 each take a "result" argument and construct variables of
 297    *  the appropriate functor type.
 298    *
 299    *  @addtogroup SGIextensions
 300    *  @{
 301    */
 302   /// An \link SGIextensions SGI extension \endlink.
 303   template <class _Result>
 304     struct constant_void_fun
 305     : public _Constant_void_fun<_Result>
 306     {
 307       constant_void_fun(const _Result& __v)
 308       : _Constant_void_fun<_Result>(__v) {}
 309     };
 310
 311   /// An \link SGIextensions SGI extension \endlink.
 312   template <class _Result, class _Argument = _Result>
 313     struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>
 314     {
 315       constant_unary_fun(const _Result& __v)
 316       : _Constant_unary_fun<_Result, _Argument>(__v) {}
 317     };
 318
 319   /// An \link SGIextensions SGI extension \endlink.
 320   template <class _Result, class _Arg1 = _Result, class _Arg2 = _Arg1>
 321     struct constant_binary_fun
 322     : public _Constant_binary_fun<_Result, _Arg1, _Arg2>
 323     {
 324       constant_binary_fun(const _Result& __v)
 325       : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}
 326     };
 327
 328   /// An \link SGIextensions SGI extension \endlink.
 329   template <class _Result>
 330     inline constant_void_fun<_Result>
 331     constant0(const _Result& __val)
 332     { return constant_void_fun<_Result>(__val); }
 333
 334   /// An \link SGIextensions SGI extension \endlink.
 335   template <class _Result>
 336     inline constant_unary_fun<_Result, _Result>
 337     constant1(const _Result& __val)
 338     { return constant_unary_fun<_Result, _Result>(__val); }
 339
 340   /// An \link SGIextensions SGI extension \endlink.
 341   template <class _Result>
 342     inline constant_binary_fun<_Result,_Result,_Result>
 343     constant2(const _Result& __val)
 344     { return constant_binary_fun<_Result, _Result, _Result>(__val); }
 345   /** @}  */
 346
 347   /** The @c subtractive_rng class is documented on
 348    *  <a href="http://www.sgi.com/tech/stl/">SGI's site</a>.
 349    *  Note that this code assumes that @c int is 32 bits.
 350    *
 351    *  @ingroup SGIextensions
 352    */
 353   class subtractive_rng
 354   : public unary_function<unsigned int, unsigned int>
 355   {
 356   private:
 357     unsigned int _M_table[55];
 358     size_t _M_index1;
 359     size_t _M_index2;
 360
 361   public:
 362     /// Returns a number less than the argument.
 363     unsigned int
 364     operator()(unsigned int __limit)
 365     {
 366       _M_index1 = (_M_index1 + 1) % 55;
 367       _M_index2 = (_M_index2 + 1) % 55;
 368       _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];
 369       return _M_table[_M_index1] % __limit;
 370     }
 371
 372     void
 373     _M_initialize(unsigned int __seed)
 374     {
 375       unsigned int __k = 1;
 376       _M_table[54] = __seed;
 377       size_t __i;
 378       for (__i = 0; __i < 54; __i++)
 379         {
 380           size_t __ii = (21 * (__i + 1) % 55) - 1;
 381           _M_table[__ii] = __k;
 382           __k = __seed - __k;
 383           __seed = _M_table[__ii];
 384         }
 385       for (int __loop = 0; __loop < 4; __loop++)
 386         {
 387           for (__i = 0; __i < 55; __i++)
 388             _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];
 389         }
 390       _M_index1 = 0;
 391       _M_index2 = 31;
 392     }
 393
 394     /// Ctor allowing you to initialize the seed.
 395     subtractive_rng(unsigned int __seed)
 396     { _M_initialize(__seed); }
 397
 398     /// Default ctor; initializes its state with some number you don't see.
 399     subtractive_rng()
 400     { _M_initialize(161803398u); }
 401   };
 402
 403   // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,
 404   // provided for backward compatibility, they are no longer part of
 405   // the C++ standard.
 406
 407   template <class _Ret, class _Tp, class _Arg>
 408     inline mem_fun1_t<_Ret, _Tp, _Arg>
 409     mem_fun1(_Ret (_Tp::*__f)(_Arg))
 410     { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
 411
 412   template <class _Ret, class _Tp, class _Arg>
 413     inline const_mem_fun1_t<_Ret, _Tp, _Arg>
 414     mem_fun1(_Ret (_Tp::*__f)(_Arg) const)
 415     { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
 416
 417   template <class _Ret, class _Tp, class _Arg>
 418     inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
 419     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))
 420     { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
 421
 422   template <class _Ret, class _Tp, class _Arg>
 423     inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
 424     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)
 425     { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
 426
 427 _GLIBCXX_END_NAMESPACE
 428
 429 #endif
 430