| // boost/identifier.hpp ----------------------------------------------------// |
| |
| // Copyright Beman Dawes 2006 |
| |
| // Distributed under 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 documentation at http://www.boost.org/libs/utility |
| |
| #ifndef BOOST_IDENTIFIER_HPP |
| #define BOOST_IDENTIFIER_HPP |
| |
| #include <boost/utility/enable_if.hpp> |
| #include <boost/type_traits/is_base_of.hpp> |
| #include <iosfwd> |
| |
| namespace boost |
| { |
| namespace detail |
| { |
| // class template identifier ---------------------------------------------// |
| |
| // Always used as a base class so that different instantiations result in |
| // different class types even if instantiated with the same value type T. |
| |
| // Expected usage is that T is often an integer type, best passed by |
| // value. There is no reason why T can't be a possibly larger class such as |
| // std::string, best passed by const reference. |
| |
| // This implementation uses pass by value, based on expected common uses. |
| |
| template <typename T, typename D> |
| class identifier |
| { |
| public: |
| typedef T value_type; |
| |
| const value_type value() const { return m_value; } |
| void assign( value_type v ) { m_value = v; } |
| |
| bool operator==( const D & rhs ) const { return m_value == rhs.m_value; } |
| bool operator!=( const D & rhs ) const { return m_value != rhs.m_value; } |
| bool operator< ( const D & rhs ) const { return m_value < rhs.m_value; } |
| bool operator<=( const D & rhs ) const { return m_value <= rhs.m_value; } |
| bool operator> ( const D & rhs ) const { return m_value > rhs.m_value; } |
| bool operator>=( const D & rhs ) const { return m_value >= rhs.m_value; } |
| |
| typedef void (*unspecified_bool_type)(D); // without the D, unspecified_bool_type |
| static void unspecified_bool_true(D){} // conversion allows relational operators |
| // between different identifier types |
| |
| operator unspecified_bool_type() const { return m_value == value_type() ? 0 : unspecified_bool_true; } |
| bool operator!() const { return m_value == value_type(); } |
| |
| // constructors are protected so that class can only be used as a base class |
| protected: |
| identifier() {} |
| explicit identifier( value_type v ) : m_value(v) {} |
| |
| #if !defined(BOOST_MSVC) || BOOST_MSVC > 1300 // 1300 == VC++ 7.0 bug workaround |
| private: |
| #endif |
| T m_value; |
| }; |
| |
| //#ifndef BOOST_NO_SFINAE |
| |
| // template <class Ostream, class Id> |
| // typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, |
| // Ostream & >::type operator<<( Ostream & os, const Id & id ) |
| // { |
| // return os << id.value(); |
| // } |
| |
| // template <class Istream, class Id> |
| // typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, |
| // Istream & >::type operator>>( Istream & is, Id & id ) |
| // { |
| // typename Id::value_type v; |
| // is >> v; |
| // id.value( v ); |
| // return is; |
| // } |
| //#endif |
| |
| } // namespace detail |
| } // namespace boost |
| |
| #endif // BOOST_IDENTIFIER_HPP |