std::experimental::ranges:: ForwardIterator
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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 dereferenceable 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.