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

   1 // Functor implementations -*- C++ -*-
   2
   3 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2009, 2010, 2011
   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  *  Do not attempt to use it directly. @headername{functional}
  55  */
  56
  57 #ifndef _BACKWARD_BINDERS_H
  58 #define _BACKWARD_BINDERS_H 1
  59
  60 namespace std _GLIBCXX_VISIBILITY(default)
  61 {
  62 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  63
  64   // 20.3.6 binders
  65   /** @defgroup binders Binder Classes
  66    * @ingroup functors
  67    *
  68    *  Binders turn functions/functors with two arguments into functors
  69    *  with a single argument, storing an argument to be applied later.
  70    *  For example, a variable @c B of type @c binder1st is constructed
  71    *  from a functor @c f and an argument @c x. Later, B's @c
  72    *  operator() is called with a single argument @c y. The return
  73    *  value is the value of @c f(x,y). @c B can be @a called with
  74    *  various arguments (y1, y2, ...) and will in turn call @c
  75    *  f(x,y1), @c f(x,y2), ...
  76    *
  77    *  The function @c bind1st is provided to save some typing. It takes the
  78    *  function and an argument as parameters, and returns an instance of
  79    *  @c binder1st.
  80    *
  81    *  The type @c binder2nd and its creator function @c bind2nd do the same
  82    *  thing, but the stored argument is passed as the second parameter instead
  83    *  of the first, e.g., @c bind2nd(std::minus<float>(),1.3) will create a
  84    *  functor whose @c operator() accepts a floating-point number, subtracts
  85    *  1.3 from it, and returns the result. (If @c bind1st had been used,
  86    *  the functor would perform <em>1.3 - x</em> instead.
  87    *
  88    *  Creator-wrapper functions like @c bind1st are intended to be used in
  89    *  calling algorithms. Their return values will be temporary objects.
  90    *  (The goal is to not require you to type names like
  91    *  @c std::binder1st<std::plus<int>> for declaring a variable to hold the
  92    *  return value from @c bind1st(std::plus<int>(),5).
  93    *
  94    *  These become more useful when combined with the composition functions.
  95    *
  96    *  These functions are deprecated in C++11 and can be replaced by
  97    *  @c std::bind (or @c std::tr1::bind) which is more powerful and flexible,
  98    *  supporting functions with any number of arguments.  Uses of @c bind1st
  99    *  can be replaced by @c std::bind(f, x, std::placeholders::_1) and
 100    *  @c bind2nd by @c std::bind(f, std::placeholders::_1, x).
 101    *  @{
 102    */
 103   /// One of the @link binders binder functors@endlink.
 104   template<typename _Operation>
 105     class binder1st
 106     : public unary_function<typename _Operation::second_argument_type,
 107                             typename _Operation::result_type>
 108     {
 109     protected:
 110       _Operation op;
 111       typename _Operation::first_argument_type value;
 112
 113     public:
 114       binder1st(const _Operation& __x,
 115                 const typename _Operation::first_argument_type& __y)
 116       : op(__x), value(__y) { }
 117
 118       typename _Operation::result_type
 119       operator()(const typename _Operation::second_argument_type& __x) const
 120       { return op(value, __x); }
 121
 122       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 123       // 109.  Missing binders for non-const sequence elements
 124       typename _Operation::result_type
 125       operator()(typename _Operation::second_argument_type& __x) const
 126       { return op(value, __x); }
 127     } _GLIBCXX_DEPRECATED;
 128
 129   /// One of the @link binders binder functors@endlink.
 130   template<typename _Operation, typename _Tp>
 131     inline binder1st<_Operation>
 132     bind1st(const _Operation& __fn, const _Tp& __x)
 133     {
 134       typedef typename _Operation::first_argument_type _Arg1_type;
 135       return binder1st<_Operation>(__fn, _Arg1_type(__x));
 136     }
 137
 138   /// One of the @link binders binder functors@endlink.
 139   template<typename _Operation>
 140     class binder2nd
 141     : public unary_function<typename _Operation::first_argument_type,
 142                             typename _Operation::result_type>
 143     {
 144     protected:
 145       _Operation op;
 146       typename _Operation::second_argument_type value;
 147
 148     public:
 149       binder2nd(const _Operation& __x,
 150                 const typename _Operation::second_argument_type& __y)
 151       : op(__x), value(__y) { }
 152
 153       typename _Operation::result_type
 154       operator()(const typename _Operation::first_argument_type& __x) const
 155       { return op(__x, value); }
 156
 157       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 158       // 109.  Missing binders for non-const sequence elements
 159       typename _Operation::result_type
 160       operator()(typename _Operation::first_argument_type& __x) const
 161       { return op(__x, value); }
 162     } _GLIBCXX_DEPRECATED;
 163
 164   /// One of the @link binders binder functors@endlink.
 165   template<typename _Operation, typename _Tp>
 166     inline binder2nd<_Operation>
 167     bind2nd(const _Operation& __fn, const _Tp& __x)
 168     {
 169       typedef typename _Operation::second_argument_type _Arg2_type;
 170       return binder2nd<_Operation>(__fn, _Arg2_type(__x));
 171     }
 172   /** @}  */
 173
 174 _GLIBCXX_END_NAMESPACE_VERSION
 175 } // namespace
 176
 177 #endif /* _BACKWARD_BINDERS_H */