NAME

std::input_iterator - std::input_iterator

Synopsis

Defined in header <iterator>
template<class I>

concept input_iterator =
std::input_or_output_iterator<I> && (since C++20)
std::indirectly_readable<I> &&
requires { typename /*ITER_CONCEPT*/<I>; } &&

std::derived_from</*ITER_CONCEPT*/<I>, std::input_iterator_tag>;

The input_iterator concept is a refinement of input_or_output_iterator, adding the
requirement that the referenced values can be read (via indirectly_readable) and the
requirement that the iterator concept tag be present.

Iterator concept determination

Definition of this concept is specified via an exposition-only alias template
/*ITER_CONCEPT*/.

In order to determine /*ITER_CONCEPT*/<I>, let ITER_TRAITS<I> denote I if the
specialization std::iterator_traits<I> is generated from the primary template, or
std::iterator_traits<I> otherwise:

* If ITER_TRAITS<I>::iterator_concept is valid and names a type,
/*ITER_CONCEPT*/<I> denotes the type.
* Otherwise, if ITER_TRAITS<I>::iterator_category is valid and names a type,
/*ITER_CONCEPT*/<I> denotes the type.
* Otherwise, if std::iterator_traits<I> is generated from the primary template,
/*ITER_CONCEPT*/<I> denotes std::random_access_iterator_tag.
* Otherwise, /*ITER_CONCEPT*/<I> does not denote a type and results in a
substitution failure.

Notes

Unlike the LegacyInputIterator requirements, the input_iterator concept does not
require equality_comparable, since input iterators are typically compared with
sentinels.

See also

input_or_output_iterator specifies that objects of a type can be incremented and
(C++20) dereferenced
(concept)