subrange() requires std::default_initializable<I> = default; | (1) | (since C++20) |
constexpr subrange( /*convertible-to-non-slicing*/<I> auto i, S s ) requires (!/*store-size*/); | (2) | (since C++20) |
constexpr subrange( /*convertible-to-non-slicing*/<I> auto i, S s,
/*make-unsigned-like-t*/<std::iter_difference_t<I>> n )
requires (K == ranges::subrange_kind::sized);
| (3) | (since C++20) |
template< /*different-from*/<subrange> R >
requires ranges::borrowed_range<R> &&
/*convertible-to-non-slicing*/<ranges::iterator_t<R>, I> &&
std::convertible_to<ranges::sentinel_t<R>, S>
constexpr subrange( R&& r ) requires (!/*store-size*/ || ranges::sized_range<R>);
| (4) | (since C++20) |
template< ranges::borrowed_range R>
requires /*convertible-to-non-slicing*/<ranges::iterator_t<R>, I> &&
std::convertible_to<ranges::sentinel_t<R>, S>
constexpr subrange( R&& r, /*make-unsigned-like-t*/<std::iter_difference_t<I>> n )
requires (K == ranges::subrange_kind::sized)
: subrange{ranges::begin(r), ranges::end(r), n}
{}
| (5) | (since C++20) |
Constructs a subrange.
If K == ranges::subrange_kind::sized && !std::sized_sentinel_for<S, I>, the size of the range is stored into the subrange, as if stored by a member subobject of type /*make-unsigned-like-t*/<std::iter_difference_t<I>>, where make-unsigned-like-t is an exposition-only alias template that maps each integer-like type to its corresponding unsigned version. Otherwise, the size is not stored. The constant store-size is true if the size is stored, false otherwise.
= I() and = S(), respectively. If the size is stored, it is initialized with 0 as if by the default member initializer = 0.subrange from an iterator-sentinel pair. Initializes the stored iterator and sentinel with std::move(i) and s respectively. The behavior is undefined if [i, s) is not a valid range.subrange from an iterator-sentinel pair and a size hint. Initializes the stored iterator and sentinel with std::move(i) and s respectively. If the size is stored, it is initialized with n. The behavior is undefined if [i, s) is not a valid range, or n is not equal to ranges::distance(i, s) explicitly converted to its type.subrange from a range. Equivalent to subrange(r, static_cast</*make-unsigned-like-t*/<std::iter_difference_t<I>>>(ranges::size(r))) if the size is stored. Otherwise, equivalent to subrange(ranges::begin(r), ranges::end(r)).subrange from a range and a size hint. The behavior is undefined if n is not equal to ranges::distance(ranges::begin(r), ranges::end(r)) explicitly converted to its type.The exposition only concept different-from is modeled by types T and U if and only if std::decay_t<T> and std::decay_t<U> are different types.
The exposition only concept convertible-to-non-slicing is satisfied or modeled by From and To if and only if std::convertible_to<From, To> is satisfied or modeled respectively, and any of following conditions is satisfied:
std::decay_t<From> or std::decay_t<To> is not a pointer type, std::remove_pointer_t<From>(*)[] is implicitly convertible to std::remove_pointer_t<To>(*)[], i.e., the conversion from From to To is at most a qualification conversion. | i | - | iterator that denotes the beginning of the range |
| s | - | sentinel that denotes the end of the range |
| r | - | range |
| n | - | size hint, must be equal to the size of the range |
The exposition-only concept convertible-to-non-slicing forbids the conversion from the pointer to derived class to the pointer to base class.
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3470 | C++20 | convertible-to-non-slicing rejected some valid qualification conversions | made accepted |
| P2393R1 | C++20 | implicit conversion to an integer-class type might be invalid | made explicit |
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