# ext/functional

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    00001 // Functional extensions -*- C++ -*-
    00002
    00003 // Copyright (C) 2002, 2004 Free Software Foundation, Inc.
    00004 //
    00005 // This file is part of the GNU ISO C++ Library.  This library is free
    00006 // software; you can redistribute it and/or modify it under the
    00007 // terms of the GNU General Public License as published by the
    00008 // Free Software Foundation; either version 2, or (at your option)
    00009 // any later version.
    00010
    00011 // This library is distributed in the hope that it will be useful,
    00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
    00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00014 // GNU General Public License for more details.
    00015
    00016 // You should have received a copy of the GNU General Public License along
    00017 // with this library; see the file COPYING.  If not, write to the Free
    00018 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
    00019 // USA.
    00020
    00021 // As a special exception, you may use this file as part of a free software
    00022 // library without restriction.  Specifically, if other files instantiate
    00023 // templates or use macros or inline functions from this file, or you compile
    00024 // this file and link it with other files to produce an executable, this
    00025 // file does not by itself cause the resulting executable to be covered by
    00026 // the GNU General Public License.  This exception does not however
    00027 // invalidate any other reasons why the executable file might be covered by
    00028 // the GNU General Public License.
    00029
    00030 /*
    00031  *
    00032  * Copyright (c) 1994
    00033  * Hewlett-Packard Company
    00034  *
    00035  * Permission to use, copy, modify, distribute and sell this software
    00036  * and its documentation for any purpose is hereby granted without fee,
    00037  * provided that the above copyright notice appear in all copies and
    00038  * that both that copyright notice and this permission notice appear
    00039  * in supporting documentation.  Hewlett-Packard Company makes no
    00040  * representations about the suitability of this software for any
    00041  * purpose.  It is provided "as is" without express or implied warranty.
    00042  *
    00043  *
    00044  * Copyright (c) 1996
    00045  * Silicon Graphics Computer Systems, Inc.
    00046  *
    00047  * Permission to use, copy, modify, distribute and sell this software
    00048  * and its documentation for any purpose is hereby granted without fee,
    00049  * provided that the above copyright notice appear in all copies and
    00050  * that both that copyright notice and this permission notice appear
    00051  * in supporting documentation.  Silicon Graphics makes no
    00052  * representations about the suitability of this software for any
    00053  * purpose.  It is provided "as is" without express or implied warranty.
    00054  */
    00055
    00056 /** @file ext/functional
    00057  *  This file is a GNU extension to the Standard C++ Library (possibly
    00058  *  containing extensions from the HP/SGI STL subset).
    00059  */
    00060
    00061 #ifndef _EXT_FUNCTIONAL
    00062 #define _EXT_FUNCTIONAL 1
    00063
    00064 #pragma GCC system_header
    00065
    00066 #include <functional>
    00067
    00068 namespace __gnu_cxx
    00069 {
    00070   using std::unary_function;
    00071   using std::binary_function;
    00072   using std::mem_fun1_t;
    00073   using std::const_mem_fun1_t;
    00074   using std::mem_fun1_ref_t;
    00075   using std::const_mem_fun1_ref_t;
    00076
    00077   /** The @c identity_element functions are not part of the C++ standard; SGI
    00078    *  provided them as an extension.  Its argument is an operation, and its
    00079    *  return value is the identity element for that operation.  It is overloaded
    00080    *  for addition and multiplication, and you can overload it for your own
    00081    *  nefarious operations.
    00082    *
    00083    *  @addtogroup SGIextensions
    00084    *  @{
    00085    */
    00086   /// An \link SGIextensions SGI extension \endlink.
    00087   template <class _Tp>
    00088     inline _Tp
    00089     identity_element(std::plus<_Tp>)
    00090     { return _Tp(0); }
    00091
    00092   /// An \link SGIextensions SGI extension \endlink.
    00093   template <class _Tp>
    00094     inline _Tp
    00095     identity_element(std::multiplies<_Tp>)
    00096     { return _Tp(1); }
    00097   /** @}  */
    00098
    00099   /** As an extension to the binders, SGI provided composition functors and
    00100    *  wrapper functions to aid in their creation.  The @c unary_compose
    00101    *  functor is constructed from two functions/functors, @c f and @c g.
    00102    *  Calling @c operator() with a single argument @c x returns @c f(g(x)).
    00103    *  The function @c compose1 takes the two functions and constructs a
    00104    *  @c unary_compose variable for you.
    00105    *
    00106    *  @c binary_compose is constructed from three functors, @c f, @c g1,
    00107    *  and @c g2.  Its @c operator() returns @c f(g1(x),g2(x)).  The function
    00108    *  @compose2 takes f, g1, and g2, and constructs the @c binary_compose
    00109    *  instance for you.  For example, if @c f returns an int, then
    00110    *  \code
    00111    *  int answer = (compose2(f,g1,g2))(x);
    00112    *  \endcode
    00113    *  is equivalent to
    00114    *  \code
    00115    *  int temp1 = g1(x);
    00116    *  int temp2 = g2(x);
    00117    *  int answer = f(temp1,temp2);
    00118    *  \endcode
    00119    *  But the first form is more compact, and can be passed around as a
    00120    *  functor to other algorithms.
    00121    *
    00122    *  @addtogroup SGIextensions
    00123    *  @{
    00124    */
    00125   /// An \link SGIextensions SGI extension \endlink.
    00126   template <class _Operation1, class _Operation2>
    00127     class unary_compose
    00128     : public unary_function<typename _Operation2::argument_type,
    00129                 typename _Operation1::result_type>
    00130     {
    00131     protected:
    00132       _Operation1 _M_fn1;
    00133       _Operation2 _M_fn2;
    00134
    00135     public:
    00136       unary_compose(const _Operation1& __x, const _Operation2& __y)
    00137       : _M_fn1(__x), _M_fn2(__y) {}
    00138
    00139       typename _Operation1::result_type
    00140       operator()(const typename _Operation2::argument_type& __x) const
    00141       { return _M_fn1(_M_fn2(__x)); }
    00142     };
    00143
    00144   /// An \link SGIextensions SGI extension \endlink.
    00145   template <class _Operation1, class _Operation2>
    00146     inline unary_compose<_Operation1, _Operation2>
    00147     compose1(const _Operation1& __fn1, const _Operation2& __fn2)
    00148     { return unary_compose<_Operation1,_Operation2>(__fn1, __fn2); }
    00149
    00150   /// An \link SGIextensions SGI extension \endlink.
    00151   template <class _Operation1, class _Operation2, class _Operation3>
    00152     class binary_compose
    00153     : public unary_function<typename _Operation2::argument_type,
    00154                 typename _Operation1::result_type>
    00155     {
    00156     protected:
    00157       _Operation1 _M_fn1;
    00158       _Operation2 _M_fn2;
    00159       _Operation3 _M_fn3;
    00160
    00161     public:
    00162       binary_compose(const _Operation1& __x, const _Operation2& __y,
    00163              const _Operation3& __z)
    00164       : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }
    00165
    00166       typename _Operation1::result_type
    00167       operator()(const typename _Operation2::argument_type& __x) const
    00168       { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }
    00169     };
    00170
    00171   /// An \link SGIextensions SGI extension \endlink.
    00172   template <class _Operation1, class _Operation2, class _Operation3>
    00173     inline binary_compose<_Operation1, _Operation2, _Operation3>
    00174     compose2(const _Operation1& __fn1, const _Operation2& __fn2,
    00175          const _Operation3& __fn3)
    00176     { return binary_compose<_Operation1, _Operation2, _Operation3>
    00177     (__fn1, __fn2, __fn3); }
    00178   /** @}  */
    00179
    00180   /** As an extension, SGI provided a functor called @c identity.  When a
    00181    *  functor is required but no operations are desired, this can be used as a
    00182    *  pass-through.  Its @c operator() returns its argument unchanged.
    00183    *
    00184    *  @addtogroup SGIextensions
    00185    */
    00186   template <class _Tp>
    00187     struct identity : public std::_Identity<_Tp> {};
    00188
    00189   /** @c select1st and @c select2nd are extensions provided by SGI.  Their
    00190    *  @c operator()s
    00191    *  take a @c std::pair as an argument, and return either the first member
    00192    *  or the second member, respectively.  They can be used (especially with
    00193    *  the composition functors) to "strip" data from a sequence before
    00194    *  performing the remainder of an algorithm.
    00195    *
    00196    *  @addtogroup SGIextensions
    00197    *  @{
    00198    */
    00199   /// An \link SGIextensions SGI extension \endlink.
    00200   template <class _Pair>
    00201     struct select1st : public std::_Select1st<_Pair> {};
    00202
    00203   /// An \link SGIextensions SGI extension \endlink.
    00204   template <class _Pair>
    00205     struct select2nd : public std::_Select2nd<_Pair> {};
    00206   /** @}  */
    00207
    00208   // extension documented next
    00209   template <class _Arg1, class _Arg2>
    00210     struct _Project1st : public binary_function<_Arg1, _Arg2, _Arg1>
    00211     {
    00212       _Arg1
    00213       operator()(const _Arg1& __x, const _Arg2&) const
    00214       { return __x; }
    00215     };
    00216
    00217   template <class _Arg1, class _Arg2>
    00218     struct _Project2nd : public binary_function<_Arg1, _Arg2, _Arg2>
    00219     {
    00220       _Arg2
    00221       operator()(const _Arg1&, const _Arg2& __y) const
    00222       { return __y; }
    00223     };
    00224
    00225   /** The @c operator() of the @c project1st functor takes two arbitrary
    00226    *  arguments and returns the first one, while @c project2nd returns the
    00227    *  second one.  They are extensions provided by SGI.
    00228    *
    00229    *  @addtogroup SGIextensions
    00230    *  @{
    00231    */
    00232
    00233   /// An \link SGIextensions SGI extension \endlink.
    00234   template <class _Arg1, class _Arg2>
    00235     struct project1st : public _Project1st<_Arg1, _Arg2> {};
    00236
    00237   /// An \link SGIextensions SGI extension \endlink.
    00238   template <class _Arg1, class _Arg2>
    00239     struct project2nd : public _Project2nd<_Arg1, _Arg2> {};
    00240   /** @}  */
    00241
    00242   // extension documented next
    00243   template <class _Result>
    00244     struct _Constant_void_fun
    00245     {
    00246       typedef _Result result_type;
    00247       result_type _M_val;
    00248
    00249       _Constant_void_fun(const result_type& __v) : _M_val(__v) {}
    00250
    00251       const result_type&
    00252       operator()() const
    00253       { return _M_val; }
    00254     };
    00255
    00256   template <class _Result, class _Argument>
    00257     struct _Constant_unary_fun
    00258     {
    00259       typedef _Argument argument_type;
    00260       typedef  _Result  result_type;
    00261       result_type _M_val;
    00262
    00263       _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}
    00264
    00265       const result_type&
    00266       operator()(const _Argument&) const
    00267       { return _M_val; }
    00268     };
    00269
    00270   template <class _Result, class _Arg1, class _Arg2>
    00271     struct _Constant_binary_fun
    00272     {
    00273       typedef  _Arg1   first_argument_type;
    00274       typedef  _Arg2   second_argument_type;
    00275       typedef  _Result result_type;
    00276       _Result _M_val;
    00277
    00278       _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}
    00279
    00280       const result_type&
    00281       operator()(const _Arg1&, const _Arg2&) const
    00282       { return _M_val; }
    00283     };
    00284
    00285   /** These three functors are each constructed from a single arbitrary
    00286    *  variable/value.  Later, their @c operator()s completely ignore any
    00287    *  arguments passed, and return the stored value.
    00288    *  - @c constant_void_fun's @c operator() takes no arguments
    00289    *  - @c constant_unary_fun's @c operator() takes one argument (ignored)
    00290    *  - @c constant_binary_fun's @c operator() takes two arguments (ignored)
    00291    *
    00292    *  The helper creator functions @c constant0, @c constant1, and
    00293    *  @c constant2 each take a "result" argument and construct variables of
    00294    *  the appropriate functor type.
    00295    *
    00296    *  @addtogroup SGIextensions
    00297    *  @{
    00298    */
    00299   /// An \link SGIextensions SGI extension \endlink.
    00300   template <class _Result>
    00301     struct constant_void_fun
    00302     : public _Constant_void_fun<_Result>
    00303     {
    00304       constant_void_fun(const _Result& __v)
    00305       : _Constant_void_fun<_Result>(__v) {}
    00306     };
    00307
    00308   /// An \link SGIextensions SGI extension \endlink.
    00309   template <class _Result, class _Argument = _Result>
    00310     struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>
    00311     {
    00312       constant_unary_fun(const _Result& __v)
    00313       : _Constant_unary_fun<_Result, _Argument>(__v) {}
    00314     };
    00315
    00316   /// An \link SGIextensions SGI extension \endlink.
    00317   template <class _Result, class _Arg1 = _Result, class _Arg2 = _Arg1>
    00318     struct constant_binary_fun
    00319     : public _Constant_binary_fun<_Result, _Arg1, _Arg2>
    00320     {
    00321       constant_binary_fun(const _Result& __v)
    00322       : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}
    00323     };
    00324
    00325   /// An \link SGIextensions SGI extension \endlink.
    00326   template <class _Result>
    00327     inline constant_void_fun<_Result>
    00328     constant0(const _Result& __val)
    00329     { return constant_void_fun<_Result>(__val); }
    00330
    00331   /// An \link SGIextensions SGI extension \endlink.
    00332   template <class _Result>
    00333     inline constant_unary_fun<_Result, _Result>
    00334     constant1(const _Result& __val)
    00335     { return constant_unary_fun<_Result, _Result>(__val); }
    00336
    00337   /// An \link SGIextensions SGI extension \endlink.
    00338   template <class _Result>
    00339     inline constant_binary_fun<_Result,_Result,_Result>
    00340     constant2(const _Result& __val)
    00341     { return constant_binary_fun<_Result, _Result, _Result>(__val); }
    00342   /** @}  */
    00343
    00344   /** The @c subtractive_rng class is documented on
    00345    *  <a href="http://www.sgi.com/tech/stl/">SGI's site</a>.
    00346    *  Note that this code assumes that @c int is 32 bits.
    00347    *
    00348    *  @ingroup SGIextensions
    00349    */
    00350   class subtractive_rng
    00351   : public unary_function<unsigned int, unsigned int>
    00352   {
    00353   private:
    00354     unsigned int _M_table[55];
    00355     size_t _M_index1;
    00356     size_t _M_index2;
    00357
    00358   public:
    00359     /// Returns a number less than the argument.
    00360     unsigned int
    00361     operator()(unsigned int __limit)
    00362     {
    00363       _M_index1 = (_M_index1 + 1) % 55;
    00364       _M_index2 = (_M_index2 + 1) % 55;
    00365       _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];
    00366       return _M_table[_M_index1] % __limit;
    00367     }
    00368
    00369     void
    00370     _M_initialize(unsigned int __seed)
    00371     {
    00372       unsigned int __k = 1;
    00373       _M_table[54] = __seed;
    00374       size_t __i;
    00375       for (__i = 0; __i < 54; __i++)
    00376     {
    00377       size_t __ii = (21 * (__i + 1) % 55) - 1;
    00378       _M_table[__ii] = __k;
    00379       __k = __seed - __k;
    00380       __seed = _M_table[__ii];
    00381     }
    00382       for (int __loop = 0; __loop < 4; __loop++)
    00383     {
    00384       for (__i = 0; __i < 55; __i++)
    00385             _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];
    00386     }
    00387       _M_index1 = 0;
    00388       _M_index2 = 31;
    00389     }
    00390
    00391     /// Ctor allowing you to initialize the seed.
    00392     subtractive_rng(unsigned int __seed)
    00393     { _M_initialize(__seed); }
    00394
    00395     /// Default ctor; initializes its state with some number you don't see.
    00396     subtractive_rng()
    00397     { _M_initialize(161803398u); }
    00398   };
    00399
    00400   // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,
    00401   // provided for backward compatibility, they are no longer part of
    00402   // the C++ standard.
    00403
    00404   template <class _Ret, class _Tp, class _Arg>
    00405     inline mem_fun1_t<_Ret, _Tp, _Arg>
    00406     mem_fun1(_Ret (_Tp::*__f)(_Arg))
    00407     { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
    00408
    00409   template <class _Ret, class _Tp, class _Arg>
    00410     inline const_mem_fun1_t<_Ret, _Tp, _Arg>
    00411     mem_fun1(_Ret (_Tp::*__f)(_Arg) const)
    00412     { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
    00413
    00414   template <class _Ret, class _Tp, class _Arg>
    00415     inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
    00416     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))
    00417     { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
    00418
    00419   template <class _Ret, class _Tp, class _Arg>
    00420     inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
    00421     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)
    00422     { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
    00423 } // namespace __gnu_cxx
    00424 #endif
    00425