binders.h

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00001 // Functor implementations -*- C++ -*-
00002 
00003 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009
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) 1996-1998
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 backward/binders.h
00053  *  This is an internal header file, included by other library headers.
00054  *  You should not attempt to use it directly.
00055  */
00056 
00057 #ifndef _GLIBCXX_BINDERS_H
00058 #define _GLIBCXX_BINDERS_H 1
00059 
00060 _GLIBCXX_BEGIN_NAMESPACE(std)
00061 
00062   // 20.3.6 binders
00063   /** @defgroup binders Binder Classes
00064    * @ingroup functors
00065    *
00066    *  Binders turn functions/functors with two arguments into functors with
00067    *  a single argument, storing an argument to be applied later.  For
00068    *  example, a variable @c B of type @c binder1st is constructed from a
00069    *  functor @c f and an argument @c x.  Later, B's @c operator() is called
00070    *  with a single argument @c y.  The return value is the value of @c f(x,y).
00071    *  @c B can be "called" with various arguments (y1, y2, ...) and will in
00072    *  turn call @c f(x,y1), @c f(x,y2), ...
00073    *
00074    *  The function @c bind1st is provided to save some typing.  It takes the
00075    *  function and an argument as parameters, and returns an instance of
00076    *  @c binder1st.
00077    *
00078    *  The type @c binder2nd and its creator function @c bind2nd do the same
00079    *  thing, but the stored argument is passed as the second parameter instead
00080    *  of the first, e.g., @c bind2nd(std::minus<float>,1.3) will create a
00081    *  functor whose @c operator() accepts a floating-point number, subtracts
00082    *  1.3 from it, and returns the result.  (If @c bind1st had been used,
00083    *  the functor would perform "1.3 - x" instead.
00084    *
00085    *  Creator-wrapper functions like @c bind1st are intended to be used in
00086    *  calling algorithms.  Their return values will be temporary objects.
00087    *  (The goal is to not require you to type names like
00088    *  @c std::binder1st<std::plus<int>> for declaring a variable to hold the
00089    *  return value from @c bind1st(std::plus<int>,5).
00090    *
00091    *  These become more useful when combined with the composition functions.
00092    *
00093    *  @{
00094    */
00095   /// One of the @link binders binder functors@endlink.
00096   template<typename _Operation>
00097     class binder1st
00098     : public unary_function<typename _Operation::second_argument_type,
00099                 typename _Operation::result_type>
00100     {
00101     protected:
00102       _Operation op;
00103       typename _Operation::first_argument_type value;
00104 
00105     public:
00106       binder1st(const _Operation& __x,
00107         const typename _Operation::first_argument_type& __y)
00108       : op(__x), value(__y) { }
00109 
00110       typename _Operation::result_type
00111       operator()(const typename _Operation::second_argument_type& __x) const
00112       { return op(value, __x); }
00113 
00114       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00115       // 109.  Missing binders for non-const sequence elements
00116       typename _Operation::result_type
00117       operator()(typename _Operation::second_argument_type& __x) const
00118       { return op(value, __x); }
00119     } _GLIBCXX_DEPRECATED_ATTR;
00120 
00121   /// One of the @link binders binder functors@endlink.
00122   template<typename _Operation, typename _Tp>
00123     inline binder1st<_Operation>
00124     bind1st(const _Operation& __fn, const _Tp& __x)
00125     {
00126       typedef typename _Operation::first_argument_type _Arg1_type;
00127       return binder1st<_Operation>(__fn, _Arg1_type(__x));
00128     }
00129 
00130   /// One of the @link binders binder functors@endlink.
00131   template<typename _Operation>
00132     class binder2nd
00133     : public unary_function<typename _Operation::first_argument_type,
00134                 typename _Operation::result_type>
00135     {
00136     protected:
00137       _Operation op;
00138       typename _Operation::second_argument_type value;
00139 
00140     public:
00141       binder2nd(const _Operation& __x,
00142         const typename _Operation::second_argument_type& __y)
00143       : op(__x), value(__y) { }
00144 
00145       typename _Operation::result_type
00146       operator()(const typename _Operation::first_argument_type& __x) const
00147       { return op(__x, value); }
00148 
00149       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00150       // 109.  Missing binders for non-const sequence elements
00151       typename _Operation::result_type
00152       operator()(typename _Operation::first_argument_type& __x) const
00153       { return op(__x, value); }
00154     } _GLIBCXX_DEPRECATED_ATTR;
00155 
00156   /// One of the @link binders binder functors@endlink.
00157   template<typename _Operation, typename _Tp>
00158     inline binder2nd<_Operation>
00159     bind2nd(const _Operation& __fn, const _Tp& __x)
00160     {
00161       typedef typename _Operation::second_argument_type _Arg2_type;
00162       return binder2nd<_Operation>(__fn, _Arg2_type(__x));
00163     } 
00164   /** @}  */
00165 
00166 _GLIBCXX_END_NAMESPACE
00167 
00168 #endif /* _GLIBCXX_BINDERS_H */

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