[range.prim.size] (original) (raw)

25 Ranges library [ranges]

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 toauto(extent_v<T>).
Otherwise, if disable_sized_range<remove_cv_t<T>> ([range.sized]) is false andauto(t.size()) is a valid expression of integer-like type ([iterator.concept.winc]),ranges::size(E) is expression-equivalent toauto(t.size()).
Otherwise, if T is a class or enumeration type,disable_sized_range<remove_cv_t<T>> is false andauto(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, 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.

— _end note_]

[Note 2:

Whenever ranges::size(E) is a valid expression, its type is integer-like.

— _end note_]