std::experimental::ranges::ForwardIterator (3) - Linux Manuals

std::experimental::ranges::ForwardIterator: std::experimental::ranges::ForwardIterator


std::experimental::ranges::ForwardIterator - std::experimental::ranges::ForwardIterator


Defined in header <experimental/ranges/iterator>
template < class I >
concept bool ForwardIterator =
InputIterator<I> && (ranges TS)
DerivedFrom<ranges::iterator_category_t<I>, ranges::forward_iterator_tag> &&
Incrementable<I> &&
Sentinel<I, I>;

The concept ForwardIterator<I> refines InputIterator by adding equality comparison and the multi-pass guarantee.
The domain of == for forward iterators is that of iterators over the same underlying sequence, except that value-initialized iterators of the same type may be compared with each other and shall compare equal.
Pointers and references obtained from a forward iterator into a range [i, s) must remain valid while [i, s) continues to denote a range.
Let a and b be two deferenceable iterators of type I. ForwardIterator<I> is satisfied only if:

* a == b implies ++a == ++b; and
* The expression ([](X x){++x;}(a), *a) is equivalent to *a, i.e., incrementing a copy of a has no effect on the result of dereferencing a.

This is known as the multi-pass guarantee.


A forward iterator cannot be "stashing": it cannot return a reference to an object within itself, because such references would be invalidated by the destruction of the forward iterator.