boost/utility/compare_pointees.hpp

   1 // Copyright (C) 2003, Fernando Luis Cacciola Carballal.
   2 //
   3 // Use, modification, and distribution is subject to the Boost Software
   4 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   5 // http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // See http://www.boost.org/lib/optional for documentation.
   8 //
   9 // You are welcome to contact the author at:
  10 //  fernando_cacciola@hotmail.com
  11 //
  12 #ifndef BOOST_UTILITY_COMPARE_POINTEES_25AGO2003_HPP
  13 #define BOOST_UTILITY_COMPARE_POINTEES_25AGO2003_HPP
  14
  15 #include<functional>
  16
  17 namespace boost {
  18
  19 // template<class OP> bool equal_pointees(OP const& x, OP const& y);
  20 // template<class OP> struct equal_pointees_t;
  21 //
  22 // Being OP a model of OptionalPointee (either a pointer or an optional):
  23 //
  24 // If both x and y have valid pointees, returns the result of (*x == *y)
  25 // If only one has a valid pointee, returns false.
  26 // If none have valid pointees, returns true.
  27 // No-throw
  28 template<class OptionalPointee>
  29 inline
  30 bool equal_pointees ( OptionalPointee const& x, OptionalPointee const& y )
  31 {
  32   return (!x) != (!y) ? false : ( !x ? true : (*x) == (*y) ) ;
  33 }
  34
  35 template<class OptionalPointee>
  36 struct equal_pointees_t : std::binary_function<OptionalPointee,OptionalPointee,bool>
  37 {
  38   bool operator() ( OptionalPointee const& x, OptionalPointee const& y ) const
  39     { return equal_pointees(x,y) ; }
  40 } ;
  41
  42 // template<class OP> bool less_pointees(OP const& x, OP const& y);
  43 // template<class OP> struct less_pointees_t;
  44 //
  45 // Being OP a model of OptionalPointee (either a pointer or an optional):
  46 //
  47 // If y has not a valid pointee, returns false.
  48 // ElseIf x has not a valid pointee, returns true.
  49 // ElseIf both x and y have valid pointees, returns the result of (*x < *y)
  50 // No-throw
  51 template<class OptionalPointee>
  52 inline
  53 bool less_pointees ( OptionalPointee const& x, OptionalPointee const& y )
  54 {
  55   return !y ? false : ( !x ? true : (*x) < (*y) ) ;
  56 }
  57
  58 template<class OptionalPointee>
  59 struct less_pointees_t : std::binary_function<OptionalPointee,OptionalPointee,bool>
  60 {
  61   bool operator() ( OptionalPointee const& x, OptionalPointee const& y ) const
  62     { return less_pointees(x,y) ; }
  63 } ;
  64
  65 } // namespace boost
  66
  67 #endif
  68