26 Ranges library [ranges]

26.7 Range adaptors [range.adaptors]

26.7.21 Reverse view [range.reverse] Overview [range.reverse.overview]

reverse_view takes a bidirectional view and produces another view that iterates the same elements in reverse order.
The name views​::​reverse denotes a range adaptor object ([range.adaptor.object]).
Given a subexpression E, the expression views​::​reverse(E) is expression-equivalent to:
  • If the type of E is a (possibly cv-qualified) specialization of reverse_view, equivalent to E.base().
  • Otherwise, if the type of E is cv subrange<reverse_iterator<I>, reverse_iterator<I>, K> for some iterator type I and value K of type subrange_kind,
    • if K is subrange_kind​::​sized, equivalent to: subrange<I, I, K>(E.end().base(), E.begin().base(), E.size())
    • otherwise, equivalent to: subrange<I, I, K>(E.end().base(), E.begin().base())
    However, in either case E is evaluated only once.
  • Otherwise, equivalent to reverse_view{E}.
[Example 1: vector<int> is {0,1,2,3,4}; for (int i : is | views::reverse) cout << i << ' '; // prints 4 3 2 1 0 — end example]