// Copyright (C) 2003, Fernando Luis Cacciola Carballal.

 //

 // Use, modification, and distribution is subject to the Boost Software

 // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at

 // http://www.boost.org/LICENSE_1_0.txt)

 //

 // See http://www.boost.org/lib/optional for documentation.

 //

 // You are welcome to contact the author at:

 //  fernando_cacciola@hotmail.com

 //

 #ifndef BOOST_UTILITY_COMPARE_POINTEES_25AGO2003_HPP

 #define BOOST_UTILITY_COMPARE_POINTEES_25AGO2003_HPP

 #include<functional>

 namespace boost {

 // template<class OP> bool equal_pointees(OP const& x, OP const& y);

 // template<class OP> struct equal_pointees_t;

 //

 // Being OP a model of OptionalPointee (either a pointer or an optional):

 //

 // If both x and y have valid pointees, returns the result of (*x == *y)

 // If only one has a valid pointee, returns false.

 // If none have valid pointees, returns true.

 // No-throw

 template<class OptionalPointee>

 inline

 bool equal_pointees ( OptionalPointee const& x, OptionalPointee const& y )

 {

   return (!x) != (!y) ? false : ( !x ? true : (*x) == (*y) ) ;

 }

 template<class OptionalPointee>

 struct equal_pointees_t : std::binary_function<OptionalPointee,OptionalPointee,bool>

 {

   bool operator() ( OptionalPointee const& x, OptionalPointee const& y ) const

     { return equal_pointees(x,y) ; }

 } ;

 // template<class OP> bool less_pointees(OP const& x, OP const& y);

 // template<class OP> struct less_pointees_t;

 //

 // Being OP a model of OptionalPointee (either a pointer or an optional):

 //

 // If y has not a valid pointee, returns false.

 // ElseIf x has not a valid pointee, returns true.

 // ElseIf both x and y have valid pointees, returns the result of (*x < *y)

 // No-throw

 template<class OptionalPointee>

 inline

 bool less_pointees ( OptionalPointee const& x, OptionalPointee const& y )

 {

   return !y ? false : ( !x ? true : (*x) < (*y) ) ;

 }

 template<class OptionalPointee>

 struct less_pointees_t : std::binary_function<OptionalPointee,OptionalPointee,bool>

 {

   bool operator() ( OptionalPointee const& x, OptionalPointee const& y ) const

     { return less_pointees(x,y) ; }

 } ;

 } // namespace boost

 #endif