24 Ranges library [ranges]

24.7 Range adaptors [range.adaptors]

24.7.4 Filter view [range.filter]

24.7.4.5 views​::​filter [range.filter.adaptor]

The name views​::​filter denotes a range adaptor object ([range.adaptor.object]).
For some subexpressions E and P, the expression views​::​filter(E, P) is expression-equivalent to filter_­view{E, P}.