libstdc++
ext/functional
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00001 // Functional extensions -*- C++ -*-
00002 
00003 // Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2009, 2010
00004 // Free Software Foundation, Inc.
00005 //
00006 // This file is part of the GNU ISO C++ Library.  This library is free
00007 // software; you can redistribute it and/or modify it under the
00008 // terms of the GNU General Public License as published by the
00009 // Free Software Foundation; either version 3, or (at your option)
00010 // any later version.
00011 
00012 // This library is distributed in the hope that it will be useful,
00013 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00014 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015 // GNU General Public License for more details.
00016 
00017 // Under Section 7 of GPL version 3, you are granted additional
00018 // permissions described in the GCC Runtime Library Exception, version
00019 // 3.1, as published by the Free Software Foundation.
00020 
00021 // You should have received a copy of the GNU General Public License and
00022 // a copy of the GCC Runtime Library Exception along with this program;
00023 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00024 // <http://www.gnu.org/licenses/>.
00025 
00026 /*
00027  *
00028  * Copyright (c) 1994
00029  * Hewlett-Packard Company
00030  *
00031  * Permission to use, copy, modify, distribute and sell this software
00032  * and its documentation for any purpose is hereby granted without fee,
00033  * provided that the above copyright notice appear in all copies and
00034  * that both that copyright notice and this permission notice appear
00035  * in supporting documentation.  Hewlett-Packard Company makes no
00036  * representations about the suitability of this software for any
00037  * purpose.  It is provided "as is" without express or implied warranty.
00038  *
00039  *
00040  * Copyright (c) 1996
00041  * Silicon Graphics Computer Systems, Inc.
00042  *
00043  * Permission to use, copy, modify, distribute and sell this software
00044  * and its documentation for any purpose is hereby granted without fee,
00045  * provided that the above copyright notice appear in all copies and
00046  * that both that copyright notice and this permission notice appear
00047  * in supporting documentation.  Silicon Graphics makes no
00048  * representations about the suitability of this software for any
00049  * purpose.  It is provided "as is" without express or implied warranty.
00050  */
00051 
00052 /** @file ext/functional
00053  *  This file is a GNU extension to the Standard C++ Library (possibly
00054  *  containing extensions from the HP/SGI STL subset).
00055  */
00056 
00057 #ifndef _EXT_FUNCTIONAL
00058 #define _EXT_FUNCTIONAL 1
00059 
00060 #pragma GCC system_header
00061 
00062 #include <functional>
00063 
00064 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
00065 {
00066 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00067 
00068   using std::size_t;
00069   using std::unary_function;
00070   using std::binary_function;
00071   using std::mem_fun1_t;
00072   using std::const_mem_fun1_t;
00073   using std::mem_fun1_ref_t;
00074   using std::const_mem_fun1_ref_t;
00075 
00076   /** The @c identity_element functions are not part of the C++
00077    *  standard; SGI provided them as an extension.  Its argument is an
00078    *  operation, and its return value is the identity element for that
00079    *  operation.  It is overloaded for addition and multiplication,
00080    *  and you can overload it for your own nefarious operations.
00081    *
00082    *  @addtogroup SGIextensions
00083    *  @{
00084    */
00085   /// An \link SGIextensions SGI extension \endlink.
00086   template <class _Tp>
00087     inline _Tp
00088     identity_element(std::plus<_Tp>)
00089     { return _Tp(0); }
00090 
00091   /// An \link SGIextensions SGI extension \endlink.
00092   template <class _Tp>
00093     inline _Tp
00094     identity_element(std::multiplies<_Tp>)
00095     { return _Tp(1); }
00096   /** @}  */
00097   
00098   /** As an extension to the binders, SGI provided composition functors and
00099    *  wrapper functions to aid in their creation.  The @c unary_compose
00100    *  functor is constructed from two functions/functors, @c f and @c g.
00101    *  Calling @c operator() with a single argument @c x returns @c f(g(x)).
00102    *  The function @c compose1 takes the two functions and constructs a
00103    *  @c unary_compose variable for you.
00104    *
00105    *  @c binary_compose is constructed from three functors, @c f, @c g1,
00106    *  and @c g2.  Its @c operator() returns @c f(g1(x),g2(x)).  The function
00107    *  @compose2 takes f, g1, and g2, and constructs the @c binary_compose
00108    *  instance for you.  For example, if @c f returns an int, then
00109    *  \code
00110    *  int answer = (compose2(f,g1,g2))(x);
00111    *  \endcode
00112    *  is equivalent to
00113    *  \code
00114    *  int temp1 = g1(x);
00115    *  int temp2 = g2(x);
00116    *  int answer = f(temp1,temp2);
00117    *  \endcode
00118    *  But the first form is more compact, and can be passed around as a
00119    *  functor to other algorithms.
00120    *
00121    *  @addtogroup SGIextensions
00122    *  @{
00123    */
00124   /// An \link SGIextensions SGI extension \endlink.
00125   template <class _Operation1, class _Operation2>
00126     class unary_compose
00127     : public unary_function<typename _Operation2::argument_type,
00128                 typename _Operation1::result_type>
00129     {
00130     protected:
00131       _Operation1 _M_fn1;
00132       _Operation2 _M_fn2;
00133 
00134     public:
00135       unary_compose(const _Operation1& __x, const _Operation2& __y)
00136       : _M_fn1(__x), _M_fn2(__y) {}
00137 
00138       typename _Operation1::result_type
00139       operator()(const typename _Operation2::argument_type& __x) const
00140       { return _M_fn1(_M_fn2(__x)); }
00141     };
00142 
00143   /// An \link SGIextensions SGI extension \endlink.
00144   template <class _Operation1, class _Operation2>
00145     inline unary_compose<_Operation1, _Operation2>
00146     compose1(const _Operation1& __fn1, const _Operation2& __fn2)
00147     { return unary_compose<_Operation1,_Operation2>(__fn1, __fn2); }
00148 
00149   /// An \link SGIextensions SGI extension \endlink.
00150   template <class _Operation1, class _Operation2, class _Operation3>
00151     class binary_compose
00152     : public unary_function<typename _Operation2::argument_type,
00153                 typename _Operation1::result_type>
00154     {
00155     protected:
00156       _Operation1 _M_fn1;
00157       _Operation2 _M_fn2;
00158       _Operation3 _M_fn3;
00159       
00160     public:
00161       binary_compose(const _Operation1& __x, const _Operation2& __y,
00162              const _Operation3& __z)
00163       : _M_fn1(__x), _M_fn2(__y), _M_fn3(__z) { }
00164 
00165       typename _Operation1::result_type
00166       operator()(const typename _Operation2::argument_type& __x) const
00167       { return _M_fn1(_M_fn2(__x), _M_fn3(__x)); }
00168     };
00169 
00170   /// An \link SGIextensions SGI extension \endlink.
00171   template <class _Operation1, class _Operation2, class _Operation3>
00172     inline binary_compose<_Operation1, _Operation2, _Operation3>
00173     compose2(const _Operation1& __fn1, const _Operation2& __fn2,
00174          const _Operation3& __fn3)
00175     { return binary_compose<_Operation1, _Operation2, _Operation3>
00176     (__fn1, __fn2, __fn3); }
00177   /** @}  */
00178 
00179   /** As an extension, SGI provided a functor called @c identity.  When a
00180    *  functor is required but no operations are desired, this can be used as a
00181    *  pass-through.  Its @c operator() returns its argument unchanged.
00182    *
00183    *  @addtogroup SGIextensions
00184    */
00185   template <class _Tp>
00186     struct identity : public std::_Identity<_Tp> {};
00187 
00188   /** @c select1st and @c select2nd are extensions provided by SGI.  Their
00189    *  @c operator()s
00190    *  take a @c std::pair as an argument, and return either the first member
00191    *  or the second member, respectively.  They can be used (especially with
00192    *  the composition functors) to @a strip data from a sequence before
00193    *  performing the remainder of an algorithm.
00194    *
00195    *  @addtogroup SGIextensions
00196    *  @{
00197    */
00198   /// An \link SGIextensions SGI extension \endlink.
00199   template <class _Pair>
00200     struct select1st : public std::_Select1st<_Pair> {};
00201 
00202   /// An \link SGIextensions SGI extension \endlink.
00203   template <class _Pair>
00204     struct select2nd : public std::_Select2nd<_Pair> {};
00205   /** @}  */
00206 
00207   // extension documented next
00208   template <class _Arg1, class _Arg2>
00209     struct _Project1st : public binary_function<_Arg1, _Arg2, _Arg1>
00210     {
00211       _Arg1
00212       operator()(const _Arg1& __x, const _Arg2&) const
00213       { return __x; }
00214     };
00215 
00216   template <class _Arg1, class _Arg2>
00217     struct _Project2nd : public binary_function<_Arg1, _Arg2, _Arg2>
00218     {
00219       _Arg2
00220       operator()(const _Arg1&, const _Arg2& __y) const
00221       { return __y; }
00222     };
00223 
00224   /** The @c operator() of the @c project1st functor takes two arbitrary
00225    *  arguments and returns the first one, while @c project2nd returns the
00226    *  second one.  They are extensions provided by SGI.
00227    *
00228    *  @addtogroup SGIextensions
00229    *  @{
00230    */
00231 
00232   /// An \link SGIextensions SGI extension \endlink.
00233   template <class _Arg1, class _Arg2>
00234     struct project1st : public _Project1st<_Arg1, _Arg2> {};
00235 
00236   /// An \link SGIextensions SGI extension \endlink.
00237   template <class _Arg1, class _Arg2>
00238     struct project2nd : public _Project2nd<_Arg1, _Arg2> {};
00239   /** @}  */
00240 
00241   // extension documented next
00242   template <class _Result>
00243     struct _Constant_void_fun
00244     {
00245       typedef _Result result_type;
00246       result_type _M_val;
00247 
00248       _Constant_void_fun(const result_type& __v) : _M_val(__v) {}
00249 
00250       const result_type&
00251       operator()() const
00252       { return _M_val; }
00253     };
00254 
00255   template <class _Result, class _Argument>
00256     struct _Constant_unary_fun
00257     {
00258       typedef _Argument argument_type;
00259       typedef  _Result  result_type;
00260       result_type _M_val;
00261       
00262       _Constant_unary_fun(const result_type& __v) : _M_val(__v) {}
00263 
00264       const result_type&
00265       operator()(const _Argument&) const
00266       { return _M_val; }
00267     };
00268 
00269   template <class _Result, class _Arg1, class _Arg2>
00270     struct _Constant_binary_fun
00271     {
00272       typedef  _Arg1   first_argument_type;
00273       typedef  _Arg2   second_argument_type;
00274       typedef  _Result result_type;
00275       _Result _M_val;
00276 
00277       _Constant_binary_fun(const _Result& __v) : _M_val(__v) {}
00278       
00279       const result_type&
00280       operator()(const _Arg1&, const _Arg2&) const
00281       { return _M_val; }
00282     };
00283 
00284   /** These three functors are each constructed from a single arbitrary
00285    *  variable/value.  Later, their @c operator()s completely ignore any
00286    *  arguments passed, and return the stored value.
00287    *  - @c constant_void_fun's @c operator() takes no arguments
00288    *  - @c constant_unary_fun's @c operator() takes one argument (ignored)
00289    *  - @c constant_binary_fun's @c operator() takes two arguments (ignored)
00290    *
00291    *  The helper creator functions @c constant0, @c constant1, and
00292    *  @c constant2 each take a @a result argument and construct variables of
00293    *  the appropriate functor type.
00294    *
00295    *  @addtogroup SGIextensions
00296    *  @{
00297    */
00298   /// An \link SGIextensions SGI extension \endlink.
00299   template <class _Result>
00300     struct constant_void_fun
00301     : public _Constant_void_fun<_Result>
00302     {
00303       constant_void_fun(const _Result& __v)
00304       : _Constant_void_fun<_Result>(__v) {}
00305     };
00306 
00307   /// An \link SGIextensions SGI extension \endlink.
00308   template <class _Result, class _Argument = _Result>
00309     struct constant_unary_fun : public _Constant_unary_fun<_Result, _Argument>
00310     {
00311       constant_unary_fun(const _Result& __v)
00312       : _Constant_unary_fun<_Result, _Argument>(__v) {}
00313     };
00314 
00315   /// An \link SGIextensions SGI extension \endlink.
00316   template <class _Result, class _Arg1 = _Result, class _Arg2 = _Arg1>
00317     struct constant_binary_fun
00318     : public _Constant_binary_fun<_Result, _Arg1, _Arg2>
00319     {
00320       constant_binary_fun(const _Result& __v)
00321       : _Constant_binary_fun<_Result, _Arg1, _Arg2>(__v) {}
00322     };
00323 
00324   /// An \link SGIextensions SGI extension \endlink.
00325   template <class _Result>
00326     inline constant_void_fun<_Result>
00327     constant0(const _Result& __val)
00328     { return constant_void_fun<_Result>(__val); }
00329 
00330   /// An \link SGIextensions SGI extension \endlink.
00331   template <class _Result>
00332     inline constant_unary_fun<_Result, _Result>
00333     constant1(const _Result& __val)
00334     { return constant_unary_fun<_Result, _Result>(__val); }
00335 
00336   /// An \link SGIextensions SGI extension \endlink.
00337   template <class _Result>
00338     inline constant_binary_fun<_Result,_Result,_Result>
00339     constant2(const _Result& __val)
00340     { return constant_binary_fun<_Result, _Result, _Result>(__val); }
00341   /** @}  */
00342 
00343   /** The @c subtractive_rng class is documented on
00344    *  <a href="http://www.sgi.com/tech/stl/">SGI's site</a>.
00345    *  Note that this code assumes that @c int is 32 bits.
00346    *
00347    *  @ingroup SGIextensions
00348    */
00349   class subtractive_rng
00350   : public unary_function<unsigned int, unsigned int>
00351   {
00352   private:
00353     unsigned int _M_table[55];
00354     size_t _M_index1;
00355     size_t _M_index2;
00356 
00357   public:
00358     /// Returns a number less than the argument.
00359     unsigned int
00360     operator()(unsigned int __limit)
00361     {
00362       _M_index1 = (_M_index1 + 1) % 55;
00363       _M_index2 = (_M_index2 + 1) % 55;
00364       _M_table[_M_index1] = _M_table[_M_index1] - _M_table[_M_index2];
00365       return _M_table[_M_index1] % __limit;
00366     }
00367 
00368     void
00369     _M_initialize(unsigned int __seed)
00370     {
00371       unsigned int __k = 1;
00372       _M_table[54] = __seed;
00373       size_t __i;
00374       for (__i = 0; __i < 54; __i++)
00375     {
00376       size_t __ii = (21 * (__i + 1) % 55) - 1;
00377       _M_table[__ii] = __k;
00378       __k = __seed - __k;
00379       __seed = _M_table[__ii];
00380     }
00381       for (int __loop = 0; __loop < 4; __loop++)
00382     {
00383       for (__i = 0; __i < 55; __i++)
00384             _M_table[__i] = _M_table[__i] - _M_table[(1 + __i + 30) % 55];
00385     }
00386       _M_index1 = 0;
00387       _M_index2 = 31;
00388     }
00389 
00390     /// Ctor allowing you to initialize the seed.
00391     subtractive_rng(unsigned int __seed)
00392     { _M_initialize(__seed); }
00393 
00394     /// Default ctor; initializes its state with some number you don't see.
00395     subtractive_rng()
00396     { _M_initialize(161803398u); }
00397   };
00398 
00399   // Mem_fun adaptor helper functions mem_fun1 and mem_fun1_ref,
00400   // provided for backward compatibility, they are no longer part of
00401   // the C++ standard.
00402   
00403   template <class _Ret, class _Tp, class _Arg>
00404     inline mem_fun1_t<_Ret, _Tp, _Arg>
00405     mem_fun1(_Ret (_Tp::*__f)(_Arg))
00406     { return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
00407 
00408   template <class _Ret, class _Tp, class _Arg>
00409     inline const_mem_fun1_t<_Ret, _Tp, _Arg>
00410     mem_fun1(_Ret (_Tp::*__f)(_Arg) const)
00411     { return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
00412 
00413   template <class _Ret, class _Tp, class _Arg>
00414     inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
00415     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg))
00416     { return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
00417 
00418   template <class _Ret, class _Tp, class _Arg>
00419     inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
00420     mem_fun1_ref(_Ret (_Tp::*__f)(_Arg) const)
00421     { return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
00422 
00423 _GLIBCXX_END_NAMESPACE_VERSION
00424 } // namespace
00425 
00426 #endif
00427