std::input_or_output_iterator

Header: <iterator>

The input_or_output_iterator concept forms the basis of the iterator concept taxonomy; every iterator type satisfies the input_or_output_iterator requirements.

# Declarations

template< class I >
concept input_or_output_iterator =
requires(I i) {
{ *i } -> /*can-reference*/;
} &&
std::weakly_incrementable<I>;

(since C++20)

# Notes

input_or_output_iterator itself only specifies operations for dereferencing and incrementing an iterator. Most algorithms will require additional operations, for example:

Unlike the LegacyIterator requirements, the input_or_output_iterator concept does not require copyability.

*i is required to be equality-preserving, although the increment operations required by weakly_incrementable are not.

# Example

#include <cstddef>
#include <iterator>
 
struct SimpleIterator
{
    using difference_type = std::ptrdiff_t;
 
    int operator*();
 
    SimpleIterator& operator++();
    void operator++(int) { ++*this; }
};
 
static_assert(std::input_or_output_iterator<SimpleIterator>);