libstdc++-v3/include/backward/binders.h

   1 // Functor implementations -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009
   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) 1996-1998
  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 backward/binders.h
  58  *  This is an internal header file, included by other library headers.
  59  *  You should not attempt to use it directly.
  60  */
  61
  62 #ifndef _GLIBCXX_BINDERS_H
  63 #define _GLIBCXX_BINDERS_H 1
  64
  65 _GLIBCXX_BEGIN_NAMESPACE(std)
  66
  67   // 20.3.6 binders
  68   /** @defgroup binders Binder Classes
  69    * @ingroup functors
  70    *
  71    *  Binders turn functions/functors with two arguments into functors with
  72    *  a single argument, storing an argument to be applied later.  For
  73    *  example, a variable @c B of type @c binder1st is constructed from a
  74    *  functor @c f and an argument @c x.  Later, B's @c operator() is called
  75    *  with a single argument @c y.  The return value is the value of @c f(x,y).
  76    *  @c B can be "called" with various arguments (y1, y2, ...) and will in
  77    *  turn call @c f(x,y1), @c f(x,y2), ...
  78    *
  79    *  The function @c bind1st is provided to save some typing.  It takes the
  80    *  function and an argument as parameters, and returns an instance of
  81    *  @c binder1st.
  82    *
  83    *  The type @c binder2nd and its creator function @c bind2nd do the same
  84    *  thing, but the stored argument is passed as the second parameter instead
  85    *  of the first, e.g., @c bind2nd(std::minus<float>,1.3) will create a
  86    *  functor whose @c operator() accepts a floating-point number, subtracts
  87    *  1.3 from it, and returns the result.  (If @c bind1st had been used,
  88    *  the functor would perform "1.3 - x" instead.
  89    *
  90    *  Creator-wrapper functions like @c bind1st are intended to be used in
  91    *  calling algorithms.  Their return values will be temporary objects.
  92    *  (The goal is to not require you to type names like
  93    *  @c std::binder1st<std::plus<int>> for declaring a variable to hold the
  94    *  return value from @c bind1st(std::plus<int>,5).
  95    *
  96    *  These become more useful when combined with the composition functions.
  97    *
  98    *  @{
  99    */
 100   /// One of the @link binders binder functors@endlink.
 101   template<typename _Operation>
 102     class binder1st
 103     : public unary_function<typename _Operation::second_argument_type,
 104                             typename _Operation::result_type>
 105     {
 106     protected:
 107       _Operation op;
 108       typename _Operation::first_argument_type value;
 109
 110     public:
 111       binder1st(const _Operation& __x,
 112                 const typename _Operation::first_argument_type& __y)
 113       : op(__x), value(__y) { }
 114
 115       typename _Operation::result_type
 116       operator()(const typename _Operation::second_argument_type& __x) const
 117       { return op(value, __x); }
 118
 119       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 120       // 109.  Missing binders for non-const sequence elements
 121       typename _Operation::result_type
 122       operator()(typename _Operation::second_argument_type& __x) const
 123       { return op(value, __x); }
 124     } _GLIBCXX_DEPRECATED_ATTR;
 125
 126   /// One of the @link binders binder functors@endlink.
 127   template<typename _Operation, typename _Tp>
 128     inline binder1st<_Operation>
 129     bind1st(const _Operation& __fn, const _Tp& __x)
 130     {
 131       typedef typename _Operation::first_argument_type _Arg1_type;
 132       return binder1st<_Operation>(__fn, _Arg1_type(__x));
 133     }
 134
 135   /// One of the @link binders binder functors@endlink.
 136   template<typename _Operation>
 137     class binder2nd
 138     : public unary_function<typename _Operation::first_argument_type,
 139                             typename _Operation::result_type>
 140     {
 141     protected:
 142       _Operation op;
 143       typename _Operation::second_argument_type value;
 144
 145     public:
 146       binder2nd(const _Operation& __x,
 147                 const typename _Operation::second_argument_type& __y)
 148       : op(__x), value(__y) { }
 149
 150       typename _Operation::result_type
 151       operator()(const typename _Operation::first_argument_type& __x) const
 152       { return op(__x, value); }
 153
 154       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 155       // 109.  Missing binders for non-const sequence elements
 156       typename _Operation::result_type
 157       operator()(typename _Operation::first_argument_type& __x) const
 158       { return op(__x, value); }
 159     } _GLIBCXX_DEPRECATED_ATTR;
 160
 161   /// One of the @link binders binder functors@endlink.
 162   template<typename _Operation, typename _Tp>
 163     inline binder2nd<_Operation>
 164     bind2nd(const _Operation& __fn, const _Tp& __x)
 165     {
 166       typedef typename _Operation::second_argument_type _Arg2_type;
 167       return binder2nd<_Operation>(__fn, _Arg2_type(__x));
 168     }
 169   /** @}  */
 170
 171 _GLIBCXX_END_NAMESPACE
 172
 173 #endif /* _GLIBCXX_BINDERS_H */