std::experimental::ranges::ForwardIterator
| Defined in header <experimental/ranges/iterator>
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| template < class I > concept bool ForwardIterator = |
(ranges TS) | |
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
ahas no effect on the result of dereferencinga.
This is known as the multi-pass guarantee.
Notes
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.