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
51namespace boost {
52namespace lambda {
53
54#define BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE(INDEX) \
55 \
56namespace detail { \
57 \
58template <template<BOOST_LAMBDA_CLASS_LIST(INDEX,T)> class F> \
59struct 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 \
67template <class From, template <BOOST_LAMBDA_CLASS_LIST(INDEX,T)> class To> \
68struct 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 \
76public: \
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
85BOOST_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
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