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implementation now uses is_convertible to deal with bugs in different

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compilers


[SVN r12216]
This commit is contained in:
Jaakko Järvi
2002-01-04 21:00:10 +00:00
parent cd6db4a38c
commit 006d968e5a
1 changed files with 43 additions and 59 deletions
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102
include/boost/lambda/detail/is_instance_of.hpp
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@@ -18,6 +18,8 @@
#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"
@@ -32,76 +34,55 @@
// Example:
// is_instance_of_2<std::istream, basic_stream>::value == true
// Vesa Karvonen's preprocessor library is not part of boost (yet), so
// the relevant headers are under boost/lambda/detail
// 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(N,A) BOOST_PP_COMMA_IF(N) class
#define BOOST_LAMBDA_CLASS_ARG(N,A) BOOST_PP_COMMA_IF(N) class T##N
#define BOOST_LAMBDA_ARG(N,A) BOOST_PP_COMMA_IF(N) T##N
#define BOOST_LAMBDA_CLASS_ARG(N,A) BOOST_PP_COMMA_IF(N) class A##N
#define BOOST_LAMBDA_ARG(N,A) BOOST_PP_COMMA_IF(N) A##N
#define BOOST_LAMBDA_CLASS_LIST(n) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS, FOO)
#define BOOST_LAMBDA_CLASS_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS, NAME)
#define BOOST_LAMBDA_CLASS_ARG_LIST(n) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS_ARG, FOO)
#define BOOST_LAMBDA_CLASS_ARG_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_CLASS_ARG, NAME)
#define BOOST_LAMBDA_ARG_LIST(n) BOOST_PP_REPEAT(n, BOOST_LAMBDA_ARG, FOO)
#define BOOST_LAMBDA_ARG_LIST(n, NAME) BOOST_PP_REPEAT(n, BOOST_LAMBDA_ARG, NAME)
namespace boost {
namespace lambda {
namespace detail {
typedef char yes_type;
typedef double no_type;
#ifndef __GNUC__
// store a pointer, as passing non-PODs through ellipsis results in
// warnings in some compilers
#define BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE(INDEX) \
template <class From, template <BOOST_LAMBDA_CLASS_LIST(INDEX)> class To> \
struct BOOST_PP_CAT(is_instance_of_,INDEX) \
{ \
private: \
static no_type _m_check(...); \
\
template <BOOST_LAMBDA_CLASS_ARG_LIST(INDEX)> \
static yes_type _m_check(const To<BOOST_LAMBDA_ARG_LIST(INDEX)>*); \
\
static From* _m_from; \
\
public: \
static const bool value = sizeof( _m_check(_m_from) ) == sizeof(yes_type); \
void foo(); \
#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); \
};
#else
// GCC version
#define BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE(INDEX) \
template <class From, template <BOOST_LAMBDA_CLASS_LIST(INDEX)> class To> \
struct BOOST_PP_CAT(is_instance_of_,INDEX) \
{ \
private: \
static no_type _m_check(...); \
\
template <BOOST_LAMBDA_CLASS_ARG_LIST(INDEX)> \
static yes_type _m_check(const To<BOOST_LAMBDA_ARG_LIST(INDEX)>*); \
\
static From* _m_from; \
\
public: \
static const bool value; \
void foo(); \
}; \
\
template <class From, template <BOOST_LAMBDA_CLASS_LIST(INDEX)> class To> \
const bool \
BOOST_PP_CAT(is_instance_of_,INDEX)<From, To>::value \
= sizeof( _m_check(_m_from) ) == sizeof(yes_type);
#endif
#define BOOST_LAMBDA_HELPER(N, A) BOOST_LAMBDA_IS_INSTANCE_OF_TEMPLATE( BOOST_PP_INC(N) )
// Generate the traits for 1-4 argument templates
@@ -117,9 +98,12 @@ BOOST_PP_REPEAT_2ND(4,BOOST_LAMBDA_HELPER,FOO)
#undef BOOST_LAMBDA_ARG_LIST
#undef BOOST_LAMBDA_CLASS_ARG_LIST
} // detail
} // lambda
} // boost
#endif