include/o3tl/compat_functional.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  *
   4  * Copyright (c) 1994
   5  * Hewlett-Packard Company
   6  *
   7  * Copyright (c) 1996-1998
   8  * Silicon Graphics Computer Systems, Inc.
   9  *
  10  * Copyright (c) 1997
  11  * Moscow Center for SPARC Technology
  12  *
  13  * Copyright (c) 1999
  14  * Boris Fomitchev
  15  *
  16  * This material is provided "as is", with absolutely no warranty expressed
  17  * or implied. Any use is at your own risk.
  18  *
  19  * Permission to use or copy this software for any purpose is hereby granted
  20  * without fee, provided the above notices are retained on all copies.
  21  * Permission to modify the code and to distribute modified code is granted,
  22  * provided the above notices are retained, and a notice that the code was
  23  * modified is included with the above copyright notice.
  24  *
  25  */
  26
  27 /*
  28  * Lifted and paraphrased from STLport - with additions from Fridrich
  29  * Strba and Thorsten Behrens
  30  */
  31
  32 #ifndef INCLUDED_O3TL_COMPAT_FUNCTIONAL_HXX
  33 #define INCLUDED_O3TL_COMPAT_FUNCTIONAL_HXX
  34
  35 #include <functional>
  36
  37 namespace o3tl
  38 {
  39
  40 /// Functor, given two parameters, return the first
  41 template<class T1,class T2>
  42 struct project1st : public std::binary_function<T1, T2, T1>
  43 {
  44     T1 operator()(const T1& y, const T2&) const
  45     {
  46         return y;
  47     }
  48 };
  49
  50 /// Functor, given two parameters, return the second
  51 template<class T1,class T2>
  52 struct project2nd : public std::binary_function<T1, T2, T2>
  53 {
  54     T2 operator()(const T1&, const T2& x) const
  55     {
  56         return x;
  57     }
  58 };
  59
  60 /// Select first value of a pair
  61 template<class P>
  62 struct select1st : public std::unary_function<P, typename P::first_type>
  63 {
  64     const typename P::first_type& operator()(const P& y) const
  65     {
  66         return y.first;
  67     }
  68 };
  69
  70 /// Select second value of a pair
  71 template<class P>
  72 struct select2nd : public std::unary_function<P, typename P::second_type>
  73 {
  74     const typename P::second_type& operator()(const P& y) const
  75     {
  76         return y.second;
  77     }
  78 };
  79
  80 /// Call F1 with the result of F2 applied to the one input parameter
  81 template<class F1, class F2>
  82 class unary_compose : public std::unary_function<typename F2::argument_type, typename F1::result_type>
  83 {
  84     public:
  85         unary_compose(const F1& fnction1, const F2& fnction2) : ftor1(fnction1), ftor2(fnction2) {}
  86
  87         typename F1::result_type operator()(const typename F2::argument_type& y) const
  88         {
  89             return ftor1(ftor2(y));
  90         }
  91
  92     protected:
  93         F1 ftor1;
  94         F2 ftor2;
  95 };
  96
  97 /// Create functor that calls F1 with the result of F2 applied to the one input parameter
  98 template<class F1, class F2>
  99 inline unary_compose<F1, F2> compose1(const F1& fnction1, const F2& fnction2)
 100 {
 101     return unary_compose<F1, F2>(fnction1, fnction2);
 102 }
 103
 104 }   // namespace o3tl
 105
 106 #endif
 107
 108 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */