Defined in header <ranges> | ||
|---|---|---|
template< class T >
concept sized_range = ranges::range<T> &&
requires(T& t) {
ranges::size(t);
};
| (1) | (since C++20) |
template< class > inline constexpr bool disable_sized_range = false; | (2) | (since C++20) |
sized_range concept specifies the requirements of a range type that knows its size in constant time with the size function.disable_sized_range exists to allow use of range types that provide a size function (either as a member or as a non-member) but do not in fact model sized_range. Users may specialize disable_sized_range for cv-unqualified program-defined types. Such specializations shall be usable in constant expressions and have type const bool.t of type std::remove_reference_t<T>, T models sized_range only if ranges::size(t) t in a manner observable to equality-preserving expressions, and ranges::distance(ranges::begin(t), ranges::end(t)), and ranges::iterator_t<T> models forward_iterator, ranges::size(t) is well-defined regardless of the evaluation of ranges::begin(t) (in other words, a single-pass sized range may support a call to size only before the first call to begin, but a forward range must support size at all times).disable_sized_range cannot be used to opt-out a range whose iterator and sentinel satisfy sized_sentinel_for; std::disable_sized_sentinel_for must be used instead.
disable_sized_range cannot be specialized for array types or reference types.
#include <forward_list>
#include <list>
#include <ranges>
static_assert
(
std::ranges::sized_range<std::list<int>> and
not std::ranges::sized_range<std::forward_list<int>>
);
int main() {}|
(C++20) | specifies a range whose iterator type satisfies random_access_iterator (concept) |
|
(C++20) | specifies a range whose iterator type satisfies contiguous_iterator (concept) |
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