[iterator.concept.sizedsentinel] (original) (raw)
23 Iterators library [iterators]
23.3 Iterator requirements [iterator.requirements]
23.3.4 Iterator concepts [iterator.concepts]
23.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]
template<class S, class I> concept [sized_sentinel_for](#concept:sized%5Fsentinel%5Ffor "23.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]") = [sentinel_for](iterator.concept.sentinel#concept:sentinel%5Ffor "23.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<S, I> && !disable_sized_sentinel_for<remove_cv_t<S>, remove_cv_t<I>> && requires(const I& i, const S& s) { { s - i } -> [same_as](concept.same#concept:same%5Fas "18.4.2 Concept same_as [concept.same]")<iter_difference_t<I>>;{ i - s } -> [same_as](concept.same#concept:same%5Fas "18.4.2 Concept same_as [concept.same]")<iter_difference_t<I>>;};
Let i be an iterator of type I, and sa sentinel of type S such that [i, s) denotes a range.
Let N be the smallest number of applications of ++inecessary to make bool(i == s) be true.
S and I model sized_sentinel_for<S, I> only if
- If N is representable by iter_difference_t<I>, then s - i is well-defined and equals N.
- If is representable by iter_difference_t<I>, then i - s is well-defined and equals .
template<class S, class I> inline constexpr bool disable_sized_sentinel_for = false;
Remarks: Pursuant to [namespace.std], users may specialize disable_sized_sentinel_forfor cv-unqualified non-array object types S and Iif S and/or I is a program-defined type.
Such specializations shall be usable in constant expressions ([expr.const]) and have type const bool.
[Note 1:
disable_sized_sentinel_for allows use of sentinels and iterators with the library that satisfy but do not in fact model sized_sentinel_for.
— _end note_]
[Example 1:
— _end example_]