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ravamped range traits

master
Daniel Kolesa 2017-02-18 15:05:42 +01:00
parent f039fc7ed9
commit 755429f901
1 changed files with 50 additions and 27 deletions
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77
ostd/range.hh
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@ -28,36 +28,59 @@ struct random_access_range_tag: bidirectional_range_tag {};
struct finite_random_access_range_tag: random_access_range_tag {};
struct contiguous_range_tag: finite_random_access_range_tag {};
template<typename T>
struct range_half;
namespace detail {
template<typename R>
struct range_category_test {
template<typename RR>
static char test(typename RR::range_category *);
template<typename>
static int test(...);
static constexpr bool value = (sizeof(test<R>(0)) == sizeof(char));
};
#define OSTD_RANGE_TRAIT(Name, Member) \
namespace detail { \
template<typename T> \
struct range_##Name##_test { \
template<typename U> \
static char test(std::remove_reference_t<typename U::Member> *); \
template<typename U> \
static int test(...); \
static constexpr bool value = (sizeof(test<T>(0)) == sizeof(char)); \
}; \
template<typename T, bool = range_##Name##_test<T>::value> \
struct range_##Name##_base {}; \
template<typename T> \
struct range_##Name##_base<T, true> { \
using type = typename T::Member; \
}; \
} \
template<typename T> \
using range_##Name##_t = typename detail::range_##Name##_base<T>::type;
template<typename R>
constexpr bool test_range_category = range_category_test<R>::value;
OSTD_RANGE_TRAIT(category, range_category)
OSTD_RANGE_TRAIT(size, size_type)
OSTD_RANGE_TRAIT(value, value_type)
OSTD_RANGE_TRAIT(reference, reference)
OSTD_RANGE_TRAIT(difference, difference_type)
template<typename R, bool>
struct range_traits_base {};
#undef OSTD_RANGE_TRAIT
template<typename R>
struct range_traits_base<R, true> {
using range_category = typename R::range_category;
using size_type = typename R::size_type;
using value_type = typename R::value_type;
using reference = typename R::reference;
using difference_type = typename R::difference_type;
};
template<typename R, bool>
struct range_traits_impl {};
template<typename R>
struct range_traits_impl<R, true>: range_traits_base<
R,
std::is_convertible_v<typename R::range_category, input_range_tag> ||
std::is_convertible_v<typename R::range_category, output_range_tag>
> {};
}
template<typename R>
struct range_traits: detail::range_traits_impl<R, detail::test_range_category<R>> {};
template<typename R>
using range_category_t = typename range_traits<R>::range_category;
template<typename R>
using range_size_t = typename range_traits<R>::size_type;
template<typename R>
using range_value_t = typename range_traits<R>::value_type;
template<typename R>
using range_reference_t = typename range_traits<R>::reference;
template<typename R>
using range_difference_t = typename range_traits<R>::difference_type;
namespace detail {
template<typename U>