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