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