// Boost Lambda Library - is_instance_of.hpp ---------------------

 // Copyright (C) 2001 Jaakko Järvi (jaakko.jarvi@cs.utu.fi)

 //

 // Distributed under the Boost Software License, Version 1.0. (See

 // accompanying file LICENSE_1_0.txt or copy at

 // http://www.boost.org/LICENSE_1_0.txt)

 //

 // For more information, see www.boost.org

 // ---------------------------------------------------------------

 #ifndef BOOST_LAMBDA_IS_INSTANCE_OF

 #define BOOST_LAMBDA_IS_INSTANCE_OF

 #include "boost/config.hpp" // for BOOST_STATIC_CONSTANT

 #include "boost/type_traits/conversion_traits.hpp" // for is_convertible

 #include "boost/preprocessor/enum_shifted_params.hpp"

 #include "boost/preprocessor/repeat_2nd.hpp"

 // is_instance_of --------------------------------

 // 

 // is_instance_of_n<A, B>::value is true, if type A is 

 // an instantiation of a template B, or A derives from an instantiation 

 // of template B

 //

 // n is the number of template arguments for B

 // 

 // Example:

 // is_instance_of_2<std::istream, basic_stream>::value == true

 // The original implementation was somewhat different, with different versions

 // for different compilers. However, there was still a problem

 // with gcc.3.0.2 and 3.0.3 compilers, which didn't think regard

 // is_instance_of_N<...>::value was a constant.

 // John Maddock suggested the way around this problem by building 

 // is_instance_of templates using boost::is_convertible.

 // Now we only have one version of is_instance_of templates, which delagate

 // all the nasty compiler tricks to is_convertible. 

 #define BOOST_LAMBDA_CLASS(z, N,A) BOOST_PP_COMMA_IF(N) class

 #define BOOST_LAMBDA_CLASS_ARG(z, N,A) BOOST_PP_COMMA_IF(N) class A##N 

 #define BOOST_LAMBDA_ARG(z, N,A) BOOST_PP_COMMA_IF(N) A##N 

 #define BOOST_LAMBDA_CLASS_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS, NAME)

 #define BOOST_LAMBDA_CLASS_ARG_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS_ARG, NAME)

 #define BOOST_LAMBDA_ARG_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_ARG, NAME)

 namespace boost {

 namespace lambda {

 #define BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE(INDEX)                         \

                                                                             \

 namespace detail {                                                          \

                                                                             \

 template <template<BOOST_LAMBDA_CLASS_LIST(INDEX,T)> class F>               \

 struct BOOST_PP_CAT(conversion_tester_,INDEX) {                             \

   template<BOOST_LAMBDA_CLASS_ARG_LIST(INDEX,A)>                            \

   BOOST_PP_CAT(conversion_tester_,INDEX)                                    \

     (const F<BOOST_LAMBDA_ARG_LIST(INDEX,A)>&);                             \

 };                                                                          \

                                                                             \

 } /* end detail */                                                          \

                                                                             \

 template <class From, template <BOOST_LAMBDA_CLASS_LIST(INDEX,T)> class To> \

 struct BOOST_PP_CAT(is_instance_of_,INDEX)                                  \

 {                                                                           \

  private:                                                                   \

    typedef ::boost::is_convertible<                                         \

      From,                                                                  \

      BOOST_PP_CAT(detail::conversion_tester_,INDEX)<To>                     \

    > helper_type;                                                           \

                                                                             \

 public:                                                                     \

   BOOST_STATIC_CONSTANT(bool, value = helper_type::value);                  \

 };

 #define BOOST_LAMBDA_HELPER(z, N, A) BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE( BOOST_PP_INC(N) )

 // Generate the traits for 1-4 argument templates

 BOOST_PP_REPEAT_2ND(4,BOOST_LAMBDA_HELPER,FOO)

 #undef BOOST_LAMBDA_HELPER

 #undef BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE

 #undef BOOST_LAMBDA_CLASS

 #undef BOOST_LAMBDA_ARG

 #undef BOOST_LAMBDA_CLASS_ARG

 #undef BOOST_LAMBDA_CLASS_LIST

 #undef BOOST_LAMBDA_ARG_LIST

 #undef BOOST_LAMBDA_CLASS_ARG_LIST

 } // lambda

 } // boost

 #endif