23 Iterators library [iterators]

23.3 Iterator requirements [iterator.requirements]

23.3.4 Iterator concepts [iterator.concepts] Concept input_­or_­output_­iterator [iterator.concept.iterator]

The input_­or_­output_­iterator concept forms the basis of the iterator concept taxonomy; every iterator models input_­or_­output_­iterator.
This concept specifies operations for dereferencing and incrementing an iterator.
Most algorithms will require additional operations to compare iterators with sentinels ([iterator.concept.sentinel]), to read ([iterator.concept.input]) or write ([iterator.concept.output]) values, or to provide a richer set of iterator movements ([iterator.concept.forward], [iterator.concept.bidir], [iterator.concept.random.access]).
template<class I>
  concept input_or_output_iterator =
    requires(I i) {
      { *i } -> can-reference;
    } &&
Unlike the Cpp17Iterator requirements, the input_­or_­output_­iterator concept does not require copyability.
— end note