3.3 KiB
[range.prim.size]
25 Ranges library [ranges]
25.3 Range access [range.access]
25.3.10 ranges::size [range.prim.size]
The name ranges::size denotes a customization point object ([customization.point.object]).
Given a subexpression E with type T, let t be an lvalue that denotes the reified object for E.
Then:
-
If T is an array of unknown bound ([dcl.array]), ranges::size(E) is ill-formed.
-
Otherwise, if T is an array type, ranges::size(E) is expression-equivalent to auto(extent_v).
-
Otherwise, if disable_sized_range<remove_cv_t> ([range.sized]) is false and auto(t.size()) is a valid expression of integer-like type ([iterator.concept.winc]), ranges::size(E) is expression-equivalent to auto(t.size()).
-
Otherwise, if T is a class or enumeration type, disable_sized_range<remove_cv_t> is false and auto(size(t)) is a valid expression of integer-like type where the meaning of size is established as-if by performing argument-dependent lookup only ([basic.lookup.argdep]), then ranges::size(E) is expression-equivalent to that expression.
-
Otherwise, if to-unsigned-like(ranges::end(t) - ranges::begin(t)) ([ranges.syn]) is a valid expression and the types I and S of ranges::begin(t) and ranges::end(t) (respectively) model both sized_sentinel_for<S, I> ([iterator.concept.sizedsentinel]) and forward_iterator, then ranges::size(E) is expression-equivalent to to-unsigned-like(ranges::end(t) - ranges::begin(t)).
-
Otherwise, ranges::size(E) is ill-formed.
[Note 1:
Diagnosable ill-formed cases above result in substitution failure when ranges::size(E) appears in the immediate context of a template instantiation.
â end note]
[Note 2:
Whenever ranges::size(E) is a valid expression, its type is integer-like.
â end note]