24 Iterators library [iterators]

24.5 Iterator adaptors [predef.iterators]

24.5.6 Default sentinel [default.sentinel]

namespace std { struct default_sentinel_t { }; }
Class default_sentinel_t is an empty type used to denote the end of a range.
It can be used together with iterator types that know the bound of their range (e.g., counted_iterator ([counted.iterator])).