williamr@2: // Boost Lambda Library - is_instance_of.hpp ---------------------
williamr@2: 
williamr@2: // Copyright (C) 2001 Jaakko Järvi (jaakko.jarvi@cs.utu.fi)
williamr@2: //
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: //
williamr@2: // For more information, see www.boost.org
williamr@2: 
williamr@2: // ---------------------------------------------------------------
williamr@2: 
williamr@2: #ifndef BOOST_LAMBDA_IS_INSTANCE_OF
williamr@2: #define BOOST_LAMBDA_IS_INSTANCE_OF
williamr@2: 
williamr@2: #include "boost/config.hpp" // for BOOST_STATIC_CONSTANT
williamr@2: #include "boost/type_traits/conversion_traits.hpp" // for is_convertible
williamr@2: #include "boost/preprocessor/enum_shifted_params.hpp"
williamr@2: #include "boost/preprocessor/repeat_2nd.hpp"
williamr@2: 
williamr@2: // is_instance_of --------------------------------
williamr@2: // 
williamr@2: // is_instance_of_n<A, B>::value is true, if type A is 
williamr@2: // an instantiation of a template B, or A derives from an instantiation 
williamr@2: // of template B
williamr@2: //
williamr@2: // n is the number of template arguments for B
williamr@2: // 
williamr@2: // Example:
williamr@2: // is_instance_of_2<std::istream, basic_stream>::value == true
williamr@2: 
williamr@2: // The original implementation was somewhat different, with different versions
williamr@2: // for different compilers. However, there was still a problem
williamr@2: // with gcc.3.0.2 and 3.0.3 compilers, which didn't think regard
williamr@2: // is_instance_of_N<...>::value was a constant.
williamr@2: // John Maddock suggested the way around this problem by building 
williamr@2: // is_instance_of templates using boost::is_convertible.
williamr@2: // Now we only have one version of is_instance_of templates, which delagate
williamr@2: // all the nasty compiler tricks to is_convertible. 
williamr@2: 
williamr@2: #define BOOST_LAMBDA_CLASS(z, N,A) BOOST_PP_COMMA_IF(N) class
williamr@2: #define BOOST_LAMBDA_CLASS_ARG(z, N,A) BOOST_PP_COMMA_IF(N) class A##N 
williamr@2: #define BOOST_LAMBDA_ARG(z, N,A) BOOST_PP_COMMA_IF(N) A##N 
williamr@2: 
williamr@2: #define BOOST_LAMBDA_CLASS_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS, NAME)
williamr@2: 
williamr@2: #define BOOST_LAMBDA_CLASS_ARG_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS_ARG, NAME)
williamr@2: 
williamr@2: #define BOOST_LAMBDA_ARG_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_ARG, NAME)
williamr@2: 
williamr@2: namespace boost {
williamr@2: namespace lambda {
williamr@2: 
williamr@2: #define BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE(INDEX)                         \
williamr@2:                                                                             \
williamr@2: namespace detail {                                                          \
williamr@2:                                                                             \
williamr@2: template <template<BOOST_LAMBDA_CLASS_LIST(INDEX,T)> class F>               \
williamr@2: struct BOOST_PP_CAT(conversion_tester_,INDEX) {                             \
williamr@2:   template<BOOST_LAMBDA_CLASS_ARG_LIST(INDEX,A)>                            \
williamr@2:   BOOST_PP_CAT(conversion_tester_,INDEX)                                    \
williamr@2:     (const F<BOOST_LAMBDA_ARG_LIST(INDEX,A)>&);                             \
williamr@2: };                                                                          \
williamr@2:                                                                             \
williamr@2: } /* end detail */                                                          \
williamr@2:                                                                             \
williamr@2: template <class From, template <BOOST_LAMBDA_CLASS_LIST(INDEX,T)> class To> \
williamr@2: struct BOOST_PP_CAT(is_instance_of_,INDEX)                                  \
williamr@2: {                                                                           \
williamr@2:  private:                                                                   \
williamr@2:    typedef ::boost::is_convertible<                                         \
williamr@2:      From,                                                                  \
williamr@2:      BOOST_PP_CAT(detail::conversion_tester_,INDEX)<To>                     \
williamr@2:    > helper_type;                                                           \
williamr@2:                                                                             \
williamr@2: public:                                                                     \
williamr@2:   BOOST_STATIC_CONSTANT(bool, value = helper_type::value);                  \
williamr@2: };
williamr@2: 
williamr@2: 
williamr@2: #define BOOST_LAMBDA_HELPER(z, N, A) BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE( BOOST_PP_INC(N) )
williamr@2: 
williamr@2: // Generate the traits for 1-4 argument templates
williamr@2: 
williamr@2: BOOST_PP_REPEAT_2ND(4,BOOST_LAMBDA_HELPER,FOO)
williamr@2: 
williamr@2: #undef BOOST_LAMBDA_HELPER
williamr@2: #undef BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE
williamr@2: #undef BOOST_LAMBDA_CLASS
williamr@2: #undef BOOST_LAMBDA_ARG
williamr@2: #undef BOOST_LAMBDA_CLASS_ARG
williamr@2: #undef BOOST_LAMBDA_CLASS_LIST
williamr@2: #undef BOOST_LAMBDA_ARG_LIST
williamr@2: #undef BOOST_LAMBDA_CLASS_ARG_LIST
williamr@2: 
williamr@2: } // lambda
williamr@2: } // boost
williamr@2: 
williamr@2: #endif
williamr@2: 
williamr@2: 
williamr@2: 
williamr@2: 
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