forked from boostorg/range
more robust implementation for BOOST_RANGE_EXTRACT_OPTIONAL_TYPE
This commit is contained in:
@ -15,36 +15,32 @@
|
||||
#endif
|
||||
|
||||
#include <boost/config.hpp>
|
||||
#include <boost/preprocessor/cat.hpp>
|
||||
#include <boost/mpl/has_xxx.hpp>
|
||||
|
||||
#ifdef BOOST_NO_PARTIAL_SPECIALIZATION_IMPLICIT_DEFAULT_ARGS
|
||||
|
||||
#define BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( a_typedef ) \
|
||||
template< typename C > \
|
||||
struct extract_ ## a_typedef \
|
||||
{ \
|
||||
typedef BOOST_DEDUCED_TYPENAME C::a_typedef type; \
|
||||
};
|
||||
|
||||
#else
|
||||
|
||||
namespace boost {
|
||||
namespace range_detail {
|
||||
template< typename T > struct exists { typedef void type; };
|
||||
}
|
||||
}
|
||||
#if !defined(BOOST_MPL_CFG_NO_HAS_XXX)
|
||||
|
||||
// Defines extract_some_typedef<T> which exposes T::some_typedef as
|
||||
// extract_some_typedef<T>::type if T::some_typedef exists. Otherwise
|
||||
// extract_some_typedef<T> is empty.
|
||||
#define BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( a_typedef ) \
|
||||
template< typename C, typename Enable=void > \
|
||||
struct extract_ ## a_typedef \
|
||||
{}; \
|
||||
template< typename C > \
|
||||
struct extract_ ## a_typedef< C \
|
||||
, BOOST_DEDUCED_TYPENAME boost::range_detail::exists< BOOST_DEDUCED_TYPENAME C::a_typedef >::type \
|
||||
> { \
|
||||
typedef BOOST_DEDUCED_TYPENAME C::a_typedef type; \
|
||||
#define BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( a_typedef ) \
|
||||
BOOST_MPL_HAS_XXX_TRAIT_DEF(a_typedef) \
|
||||
template< typename C, bool B = BOOST_PP_CAT(has_, a_typedef)<C>::value > \
|
||||
struct BOOST_PP_CAT(extract_, a_typedef) \
|
||||
{}; \
|
||||
template< typename C > \
|
||||
struct BOOST_PP_CAT(extract_, a_typedef)< C, true > \
|
||||
{ \
|
||||
typedef BOOST_DEDUCED_TYPENAME C::a_typedef type; \
|
||||
};
|
||||
|
||||
#else
|
||||
|
||||
#define BOOST_RANGE_EXTRACT_OPTIONAL_TYPE( a_typedef ) \
|
||||
template< typename C > \
|
||||
struct BOOST_PP_CAT(extract_, a_typedef) \
|
||||
{ \
|
||||
typedef BOOST_DEDUCED_TYPENAME C::a_typedef type; \
|
||||
};
|
||||
|
||||
#endif
|
||||
|
Reference in New Issue
Block a user