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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
  18 // permissions described in the GCC Runtime Library Exception, version
  19 // 3.1, as published by the Free Software Foundation.
  20
  21 // You should have received a copy of the GNU General Public License and
  22 // a copy of the GCC Runtime Library Exception along with this program;
  23 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 // <http://www.gnu.org/licenses/>.
  25
  26 /*
  27  *
  28  * Copyright (c) 1994
  29  * Hewlett-Packard Company
  30  *
  31  * Permission to use, copy, modify, distribute and sell this software
  32  * and its documentation for any purpose is hereby granted without fee,
  33  * provided that the above copyright notice appear in all copies and
  34  * that both that copyright notice and this permission notice appear
  35  * in supporting documentation.  Hewlett-Packard Company makes no
  36  * representations about the suitability of this software for any
  37  * purpose.  It is provided "as is" without express or implied warranty.
  38  *
  39  *
  40  * Copyright (c) 1996-1998
  41  * Silicon Graphics Computer Systems, Inc.
  42  *
  43  * Permission to use, copy, modify, distribute and sell this software
  44  * and its documentation for any purpose is hereby granted without fee,
  45  * provided that the above copyright notice appear in all copies and
  46  * that both that copyright notice and this permission notice appear
  47  * in supporting documentation.  Silicon Graphics makes no
  48  * representations about the suitability of this software for any
  49  * purpose.  It is provided "as is" without express or implied warranty.
  50  */
  51
  52 /** @file backward/binders.h
  53  *  This is an internal header file, included by other library headers.
  54  *  You should not attempt to use it directly.
  55  */
  56
  57 #ifndef _GLIBCXX_BINDERS_H
  58 #define _GLIBCXX_BINDERS_H 1
  59
  60 _GLIBCXX_BEGIN_NAMESPACE(std)
  61
  62   // 20.3.6 binders
  63   /** @defgroup binders Binder Classes
  64    * @ingroup functors
  65    *
  66    *  Binders turn functions/functors with two arguments into functors with
  67    *  a single argument, storing an argument to be applied later.  For
  68    *  example, a variable @c B of type @c binder1st is constructed from a
  69    *  functor @c f and an argument @c x.  Later, B's @c operator() is called
  70    *  with a single argument @c y.  The return value is the value of @c f(x,y).
  71    *  @c B can be "called" with various arguments (y1, y2, ...) and will in
  72    *  turn call @c f(x,y1), @c f(x,y2), ...
  73    *
  74    *  The function @c bind1st is provided to save some typing.  It takes the
  75    *  function and an argument as parameters, and returns an instance of
  76    *  @c binder1st.
  77    *
  78    *  The type @c binder2nd and its creator function @c bind2nd do the same
  79    *  thing, but the stored argument is passed as the second parameter instead
  80    *  of the first, e.g., @c bind2nd(std::minus<float>,1.3) will create a
  81    *  functor whose @c operator() accepts a floating-point number, subtracts
  82    *  1.3 from it, and returns the result.  (If @c bind1st had been used,
  83    *  the functor would perform "1.3 - x" instead.
  84    *
  85    *  Creator-wrapper functions like @c bind1st are intended to be used in
  86    *  calling algorithms.  Their return values will be temporary objects.
  87    *  (The goal is to not require you to type names like
  88    *  @c std::binder1st<std::plus<int>> for declaring a variable to hold the
  89    *  return value from @c bind1st(std::plus<int>,5).
  90    *
  91    *  These become more useful when combined with the composition functions.
  92    *
  93    *  @{
  94    */
  95   /// One of the @link binders binder functors@endlink.
  96   template<typename _Operation>
  97     class binder1st
  98     : public unary_function<typename _Operation::second_argument_type,
  99                             typename _Operation::result_type>
 100     {
 101     protected:
 102       _Operation op;
 103       typename _Operation::first_argument_type value;
 104
 105     public:
 106       binder1st(const _Operation& __x,
 107                 const typename _Operation::first_argument_type& __y)
 108       : op(__x), value(__y) { }
 109
 110       typename _Operation::result_type
 111       operator()(const typename _Operation::second_argument_type& __x) const
 112       { return op(value, __x); }
 113
 114       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 115       // 109.  Missing binders for non-const sequence elements
 116       typename _Operation::result_type
 117       operator()(typename _Operation::second_argument_type& __x) const
 118       { return op(value, __x); }
 119     } _GLIBCXX_DEPRECATED_ATTR;
 120
 121   /// One of the @link binders binder functors@endlink.
 122   template<typename _Operation, typename _Tp>
 123     inline binder1st<_Operation>
 124     bind1st(const _Operation& __fn, const _Tp& __x)
 125     {
 126       typedef typename _Operation::first_argument_type _Arg1_type;
 127       return binder1st<_Operation>(__fn, _Arg1_type(__x));
 128     }
 129
 130   /// One of the @link binders binder functors@endlink.
 131   template<typename _Operation>
 132     class binder2nd
 133     : public unary_function<typename _Operation::first_argument_type,
 134                             typename _Operation::result_type>
 135     {
 136     protected:
 137       _Operation op;
 138       typename _Operation::second_argument_type value;
 139
 140     public:
 141       binder2nd(const _Operation& __x,
 142                 const typename _Operation::second_argument_type& __y)
 143       : op(__x), value(__y) { }
 144
 145       typename _Operation::result_type
 146       operator()(const typename _Operation::first_argument_type& __x) const
 147       { return op(__x, value); }
 148
 149       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 150       // 109.  Missing binders for non-const sequence elements
 151       typename _Operation::result_type
 152       operator()(typename _Operation::first_argument_type& __x) const
 153       { return op(__x, value); }
 154     } _GLIBCXX_DEPRECATED_ATTR;
 155
 156   /// One of the @link binders binder functors@endlink.
 157   template<typename _Operation, typename _Tp>
 158     inline binder2nd<_Operation>
 159     bind2nd(const _Operation& __fn, const _Tp& __x)
 160     {
 161       typedef typename _Operation::second_argument_type _Arg2_type;
 162       return binder2nd<_Operation>(__fn, _Arg2_type(__x));
 163     }
 164   /** @}  */
 165
 166 _GLIBCXX_END_NAMESPACE
 167
 168 #endif /* _GLIBCXX_BINDERS_H */