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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