[3408] | 1 | // boost/identifier.hpp ----------------------------------------------------// |
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| 2 | |
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| 3 | // Copyright Beman Dawes 2006 |
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| 4 | |
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| 5 | // Distributed under the Boost Software License, Version 1.0. (See accompanying |
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| 6 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
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| 7 | |
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| 8 | // See documentation at http://www.boost.org/libs/utility |
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| 9 | |
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| 10 | #ifndef BOOST_IDENTIFIER_HPP |
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| 11 | #define BOOST_IDENTIFIER_HPP |
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| 12 | |
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| 13 | #include <boost/utility/enable_if.hpp> |
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| 14 | #include <boost/type_traits/is_base_of.hpp> |
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| 15 | #include <iosfwd> |
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| 16 | |
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| 17 | namespace boost |
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| 18 | { |
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| 19 | namespace detail |
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| 20 | { |
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| 21 | // class template identifier ---------------------------------------------// |
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| 22 | |
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| 23 | // Always used as a base class so that different instantiations result in |
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| 24 | // different class types even if instantiated with the same value type T. |
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| 25 | |
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| 26 | // Expected usage is that T is often an integer type, best passed by |
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| 27 | // value. There is no reason why T can't be a possibly larger class such as |
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| 28 | // std::string, best passed by const reference. |
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| 29 | |
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| 30 | // This implementation uses pass by value, based on expected common uses. |
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| 31 | |
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| 32 | template <typename T, typename D> |
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| 33 | class identifier |
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| 34 | { |
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| 35 | public: |
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| 36 | typedef T value_type; |
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| 37 | |
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| 38 | const value_type value() const { return m_value; } |
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| 39 | void assign( value_type v ) { m_value = v; } |
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| 40 | |
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| 41 | bool operator==( const D & rhs ) const { return m_value == rhs.m_value; } |
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| 42 | bool operator!=( const D & rhs ) const { return m_value != rhs.m_value; } |
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| 43 | bool operator< ( const D & rhs ) const { return m_value < rhs.m_value; } |
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| 44 | bool operator<=( const D & rhs ) const { return m_value <= rhs.m_value; } |
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| 45 | bool operator> ( const D & rhs ) const { return m_value > rhs.m_value; } |
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| 46 | bool operator>=( const D & rhs ) const { return m_value >= rhs.m_value; } |
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| 47 | |
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| 48 | typedef void (*unspecified_bool_type)(D); // without the D, unspecified_bool_type |
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| 49 | static void unspecified_bool_true(D){} // conversion allows relational operators |
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| 50 | // between different identifier types |
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| 51 | |
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| 52 | operator unspecified_bool_type() const { return m_value == value_type() ? 0 : unspecified_bool_true; } |
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| 53 | bool operator!() const { return m_value == value_type(); } |
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| 54 | |
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| 55 | // constructors are protected so that class can only be used as a base class |
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| 56 | protected: |
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| 57 | identifier() {} |
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| 58 | explicit identifier( value_type v ) : m_value(v) {} |
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| 59 | |
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| 60 | #if !defined(BOOST_MSVC) || BOOST_MSVC > 1300 // 1300 == VC++ 7.0 bug workaround |
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| 61 | private: |
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| 62 | #endif |
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| 63 | T m_value; |
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| 64 | }; |
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| 65 | |
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| 66 | //#ifndef BOOST_NO_SFINAE |
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| 67 | |
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| 68 | // template <class Ostream, class Id> |
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| 69 | // typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, |
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| 70 | // Ostream & >::type operator<<( Ostream & os, const Id & id ) |
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| 71 | // { |
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| 72 | // return os << id.value(); |
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| 73 | // } |
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| 74 | |
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| 75 | // template <class Istream, class Id> |
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| 76 | // typename enable_if< is_base_of< identifier< typename Id::value_type, Id >, Id >, |
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| 77 | // Istream & >::type operator>>( Istream & is, Id & id ) |
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| 78 | // { |
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| 79 | // typename Id::value_type v; |
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| 80 | // is >> v; |
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| 81 | // id.value( v ); |
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| 82 | // return is; |
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| 83 | // } |
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| 84 | //#endif |
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| 85 | |
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| 86 | } // namespace detail |
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| 87 | } // namespace boost |
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| 88 | |
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| 89 | #endif // BOOST_IDENTIFIER_HPP |
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