| 1 | // Boost Lambda Library - is_instance_of.hpp --------------------- |
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| 2 | |
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| 3 | // Copyright (C) 2001 Jaakko Jarvi (jaakko.jarvi@cs.utu.fi) |
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| 4 | // |
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| 5 | // Distributed under the Boost Software License, Version 1.0. (See |
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| 6 | // accompanying file LICENSE_1_0.txt or copy at |
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| 7 | // http://www.boost.org/LICENSE_1_0.txt) |
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| 8 | // |
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| 9 | // For more information, see www.boost.org |
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| 10 | |
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| 11 | // --------------------------------------------------------------- |
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| 12 | |
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| 13 | #ifndef BOOST_LAMBDA_IS_INSTANCE_OF |
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| 14 | #define BOOST_LAMBDA_IS_INSTANCE_OF |
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| 15 | |
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| 16 | #include "boost/config.hpp" // for BOOST_STATIC_CONSTANT |
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| 17 | #include "boost/type_traits/conversion_traits.hpp" // for is_convertible |
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| 18 | #include "boost/preprocessor/enum_shifted_params.hpp" |
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| 19 | #include "boost/preprocessor/repeat_2nd.hpp" |
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| 20 | |
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| 21 | // is_instance_of -------------------------------- |
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| 22 | // |
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| 23 | // is_instance_of_n<A, B>::value is true, if type A is |
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| 24 | // an instantiation of a template B, or A derives from an instantiation |
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| 25 | // of template B |
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| 26 | // |
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| 27 | // n is the number of template arguments for B |
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| 28 | // |
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| 29 | // Example: |
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| 30 | // is_instance_of_2<std::istream, basic_stream>::value == true |
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| 31 | |
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| 32 | // The original implementation was somewhat different, with different versions |
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| 33 | // for different compilers. However, there was still a problem |
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| 34 | // with gcc.3.0.2 and 3.0.3 compilers, which didn't think regard |
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| 35 | // is_instance_of_N<...>::value was a constant. |
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| 36 | // John Maddock suggested the way around this problem by building |
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| 37 | // is_instance_of templates using boost::is_convertible. |
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| 38 | // Now we only have one version of is_instance_of templates, which delagate |
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| 39 | // all the nasty compiler tricks to is_convertible. |
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| 40 | |
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| 41 | #define BOOST_LAMBDA_CLASS(z, N,A) BOOST_PP_COMMA_IF(N) class |
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| 42 | #define BOOST_LAMBDA_CLASS_ARG(z, N,A) BOOST_PP_COMMA_IF(N) class A##N |
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| 43 | #define BOOST_LAMBDA_ARG(z, N,A) BOOST_PP_COMMA_IF(N) A##N |
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| 44 | |
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| 45 | #define BOOST_LAMBDA_CLASS_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS, NAME) |
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| 46 | |
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| 47 | #define BOOST_LAMBDA_CLASS_ARG_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS_ARG, NAME) |
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| 48 | |
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| 49 | #define BOOST_LAMBDA_ARG_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_ARG, NAME) |
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| 50 | |
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| 51 | namespace boost { |
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| 52 | namespace lambda { |
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| 53 | |
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| 54 | #define BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE(INDEX) \ |
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| 55 | \ |
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| 56 | namespace detail { \ |
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| 57 | \ |
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| 58 | template <template<BOOST_LAMBDA_CLASS_LIST(INDEX,T)> class F> \ |
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| 59 | struct BOOST_PP_CAT(conversion_tester_,INDEX) { \ |
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| 60 | template<BOOST_LAMBDA_CLASS_ARG_LIST(INDEX,A)> \ |
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| 61 | BOOST_PP_CAT(conversion_tester_,INDEX) \ |
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| 62 | (const F<BOOST_LAMBDA_ARG_LIST(INDEX,A)>&); \ |
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| 63 | }; \ |
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| 64 | \ |
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| 65 | } /* end detail */ \ |
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| 66 | \ |
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| 67 | template <class From, template <BOOST_LAMBDA_CLASS_LIST(INDEX,T)> class To> \ |
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| 68 | struct BOOST_PP_CAT(is_instance_of_,INDEX) \ |
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| 69 | { \ |
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| 70 | private: \ |
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| 71 | typedef ::boost::is_convertible< \ |
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| 72 | From, \ |
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| 73 | BOOST_PP_CAT(detail::conversion_tester_,INDEX)<To> \ |
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| 74 | > helper_type; \ |
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| 75 | \ |
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| 76 | public: \ |
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| 77 | BOOST_STATIC_CONSTANT(bool, value = helper_type::value); \ |
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| 78 | }; |
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| 79 | |
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| 80 | |
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| 81 | #define BOOST_LAMBDA_HELPER(z, N, A) BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE( BOOST_PP_INC(N) ) |
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| 82 | |
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| 83 | // Generate the traits for 1-4 argument templates |
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| 84 | |
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| 85 | BOOST_PP_REPEAT_2ND(4,BOOST_LAMBDA_HELPER,FOO) |
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| 86 | |
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| 87 | #undef BOOST_LAMBDA_HELPER |
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| 88 | #undef BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE |
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| 89 | #undef BOOST_LAMBDA_CLASS |
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| 90 | #undef BOOST_LAMBDA_ARG |
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| 91 | #undef BOOST_LAMBDA_CLASS_ARG |
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| 92 | #undef BOOST_LAMBDA_CLASS_LIST |
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| 93 | #undef BOOST_LAMBDA_ARG_LIST |
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| 94 | #undef BOOST_LAMBDA_CLASS_ARG_LIST |
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| 95 | |
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| 96 | } // lambda |
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| 97 | } // boost |
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| 98 | |
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| 99 | #endif |
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| 100 | |
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| 101 | |
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| 102 | |
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| 103 | |
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| 104 | |
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| 105 | |
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