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89 lines
3.2 KiB
89 lines
3.2 KiB
// boost/identifier.hpp ----------------------------------------------------// |
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// Copyright Beman Dawes 2006 |
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// Distributed under the Boost Software License, Version 1.0. (See accompanying |
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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// See documentation at http://www.boost.org/libs/utility |
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#ifndef BOOST_IDENTIFIER_HPP |
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#define BOOST_IDENTIFIER_HPP |
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#include <boost/utility/enable_if.hpp> |
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#include <boost/type_traits/is_base_of.hpp> |
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#include <iosfwd> |
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namespace boost |
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{ |
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namespace detail |
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{ |
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// class template identifier ---------------------------------------------// |
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// Always used as a base class so that different instantiations result in |
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// different class types even if instantiated with the same value type T. |
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// Expected usage is that T is often an integer type, best passed by |
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// value. There is no reason why T can't be a possibly larger class such as |
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// std::string, best passed by const reference. |
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// This implementation uses pass by value, based on expected common uses. |
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template <typename T, typename D> |
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class identifier |
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{ |
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public: |
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typedef T value_type; |
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const value_type value() const { return m_value; } |
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void assign( value_type v ) { m_value = v; } |
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bool operator==( const D & rhs ) const { return m_value == rhs.m_value; } |
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bool operator!=( const D & rhs ) const { return m_value != rhs.m_value; } |
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bool operator< ( const D & rhs ) const { return m_value < rhs.m_value; } |
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bool operator<=( const D & rhs ) const { return m_value <= rhs.m_value; } |
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bool operator> ( const D & rhs ) const { return m_value > rhs.m_value; } |
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bool operator>=( const D & rhs ) const { return m_value >= rhs.m_value; } |
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typedef void (*unspecified_bool_type)(D); // without the D, unspecified_bool_type |
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static void unspecified_bool_true(D){} // conversion allows relational operators |
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// between different identifier types |
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operator unspecified_bool_type() const { return m_value == value_type() ? 0 : unspecified_bool_true; } |
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bool operator!() const { return m_value == value_type(); } |
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// constructors are protected so that class can only be used as a base class |
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protected: |
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identifier() {} |
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explicit identifier( value_type v ) : m_value(v) {} |
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#if !defined(BOOST_MSVC) || BOOST_MSVC > 1300 // 1300 == VC++ 7.0 bug workaround |
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private: |
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#endif |
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T m_value; |
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}; |
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//#ifndef BOOST_NO_SFINAE |
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// template <class Ostream, class Id> |
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// typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, |
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// Ostream & >::type operator<<( Ostream & os, const Id & id ) |
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// { |
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// return os << id.value(); |
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// } |
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// template <class Istream, class Id> |
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// typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, |
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// Istream & >::type operator>>( Istream & is, Id & id ) |
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// { |
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// typename Id::value_type v; |
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// is >> v; |
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// id.value( v ); |
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// return is; |
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// } |
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//#endif |
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} // namespace detail |
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} // namespace boost |
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#endif // BOOST_IDENTIFIER_HPP
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