constexpr reverse_iterator();
Effects:
Value-initializes
current. Iterator operations applied to the resulting iterator have defined behavior
if and only if the corresponding operations are defined on a value-initialized iterator of type
Iterator.constexpr explicit reverse_iterator(Iterator x);
Effects:
Initializes
current
with
x. template <class U> constexpr reverse_iterator(const reverse_iterator<U>& u);
Effects:
Initializes
current
with
u.current.