libstdc++
binders.h
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00001 // Functor implementations -*- C++ -*-
00002 
00003 // Copyright (C) 2001-2013 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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /*
00026  *
00027  * Copyright (c) 1994
00028  * Hewlett-Packard Company
00029  *
00030  * Permission to use, copy, modify, distribute and sell this software
00031  * and its documentation for any purpose is hereby granted without fee,
00032  * provided that the above copyright notice appear in all copies and
00033  * that both that copyright notice and this permission notice appear
00034  * in supporting documentation.  Hewlett-Packard Company makes no
00035  * representations about the suitability of this software for any
00036  * purpose.  It is provided "as is" without express or implied warranty.
00037  *
00038  *
00039  * Copyright (c) 1996-1998
00040  * Silicon Graphics Computer Systems, Inc.
00041  *
00042  * Permission to use, copy, modify, distribute and sell this software
00043  * and its documentation for any purpose is hereby granted without fee,
00044  * provided that the above copyright notice appear in all copies and
00045  * that both that copyright notice and this permission notice appear
00046  * in supporting documentation.  Silicon Graphics makes no
00047  * representations about the suitability of this software for any
00048  * purpose.  It is provided "as is" without express or implied warranty.
00049  */
00050 
00051 /** @file backward/binders.h
00052  *  This is an internal header file, included by other library headers.
00053  *  Do not attempt to use it directly. @headername{functional}
00054  */
00055 
00056 #ifndef _BACKWARD_BINDERS_H
00057 #define _BACKWARD_BINDERS_H 1
00058 
00059 namespace std _GLIBCXX_VISIBILITY(default)
00060 {
00061 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00062 
00063   // 20.3.6 binders
00064   /** @defgroup binders Binder Classes
00065    * @ingroup functors
00066    *
00067    *  Binders turn functions/functors with two arguments into functors
00068    *  with a single argument, storing an argument to be applied later.
00069    *  For example, a variable @c B of type @c binder1st is constructed
00070    *  from a functor @c f and an argument @c x. Later, B's @c
00071    *  operator() is called with a single argument @c y. The return
00072    *  value is the value of @c f(x,y). @c B can be @a called with
00073    *  various arguments (y1, y2, ...) and will in turn call @c
00074    *  f(x,y1), @c f(x,y2), ...
00075    *
00076    *  The function @c bind1st is provided to save some typing. It takes the
00077    *  function and an argument as parameters, and returns an instance of
00078    *  @c binder1st.
00079    *
00080    *  The type @c binder2nd and its creator function @c bind2nd do the same
00081    *  thing, but the stored argument is passed as the second parameter instead
00082    *  of the first, e.g., @c bind2nd(std::minus<float>(),1.3) will create a
00083    *  functor whose @c operator() accepts a floating-point number, subtracts
00084    *  1.3 from it, and returns the result. (If @c bind1st had been used,
00085    *  the functor would perform <em>1.3 - x</em> instead.
00086    *
00087    *  Creator-wrapper functions like @c bind1st are intended to be used in
00088    *  calling algorithms. Their return values will be temporary objects.
00089    *  (The goal is to not require you to type names like
00090    *  @c std::binder1st<std::plus<int>> for declaring a variable to hold the
00091    *  return value from @c bind1st(std::plus<int>(),5).
00092    *
00093    *  These become more useful when combined with the composition functions.
00094    *
00095    *  These functions are deprecated in C++11 and can be replaced by
00096    *  @c std::bind (or @c std::tr1::bind) which is more powerful and flexible,
00097    *  supporting functions with any number of arguments.  Uses of @c bind1st
00098    *  can be replaced by @c std::bind(f, x, std::placeholders::_1) and
00099    *  @c bind2nd by @c std::bind(f, std::placeholders::_1, x).
00100    *  @{
00101    */
00102   /// One of the @link binders binder functors@endlink.
00103   template<typename _Operation>
00104     class binder1st
00105     : public unary_function<typename _Operation::second_argument_type,
00106                 typename _Operation::result_type>
00107     {
00108     protected:
00109       _Operation op;
00110       typename _Operation::first_argument_type value;
00111 
00112     public:
00113       binder1st(const _Operation& __x,
00114         const typename _Operation::first_argument_type& __y)
00115       : op(__x), value(__y) { }
00116 
00117       typename _Operation::result_type
00118       operator()(const typename _Operation::second_argument_type& __x) const
00119       { return op(value, __x); }
00120 
00121       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00122       // 109.  Missing binders for non-const sequence elements
00123       typename _Operation::result_type
00124       operator()(typename _Operation::second_argument_type& __x) const
00125       { return op(value, __x); }
00126     } _GLIBCXX_DEPRECATED;
00127 
00128   /// One of the @link binders binder functors@endlink.
00129   template<typename _Operation, typename _Tp>
00130     inline binder1st<_Operation>
00131     bind1st(const _Operation& __fn, const _Tp& __x)
00132     {
00133       typedef typename _Operation::first_argument_type _Arg1_type;
00134       return binder1st<_Operation>(__fn, _Arg1_type(__x));
00135     }
00136 
00137   /// One of the @link binders binder functors@endlink.
00138   template<typename _Operation>
00139     class binder2nd
00140     : public unary_function<typename _Operation::first_argument_type,
00141                 typename _Operation::result_type>
00142     {
00143     protected:
00144       _Operation op;
00145       typename _Operation::second_argument_type value;
00146 
00147     public:
00148       binder2nd(const _Operation& __x,
00149         const typename _Operation::second_argument_type& __y)
00150       : op(__x), value(__y) { }
00151 
00152       typename _Operation::result_type
00153       operator()(const typename _Operation::first_argument_type& __x) const
00154       { return op(__x, value); }
00155 
00156       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00157       // 109.  Missing binders for non-const sequence elements
00158       typename _Operation::result_type
00159       operator()(typename _Operation::first_argument_type& __x) const
00160       { return op(__x, value); }
00161     } _GLIBCXX_DEPRECATED;
00162 
00163   /// One of the @link binders binder functors@endlink.
00164   template<typename _Operation, typename _Tp>
00165     inline binder2nd<_Operation>
00166     bind2nd(const _Operation& __fn, const _Tp& __x)
00167     {
00168       typedef typename _Operation::second_argument_type _Arg2_type;
00169       return binder2nd<_Operation>(__fn, _Arg2_type(__x));
00170     } 
00171   /** @}  */
00172 
00173 _GLIBCXX_END_NAMESPACE_VERSION
00174 } // namespace
00175 
00176 #endif /* _BACKWARD_BINDERS_H */