1 | // Boost Lambda Library - is_instance_of.hpp --------------------- |
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2 | |
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3 | // Copyright (C) 2001 Jaakko Järvi (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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