< cpp‎ | iterator
Iterator library
Iterator concepts

Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
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Range access
Defined in header <iterator>
template< class I, class T >

    concept output_iterator =
        std::input_or_output_iterator<I> &&
        std::indirectly_writable<I, T> &&
        requires(I i, T&& t) {
            *i++ = std::forward<T>(t); /* not required to be equality-preserving */

(since C++20)

The output_iterator concept is a refinement of input_or_output_iterator, adding the requirement that it can be used to write values of type and value category encoded by T (via indirectly_writable). equality_comparable is not required.


[edit] Semantic requirements

Let E be an expression such that decltype((E)) is T, and i be a dereferenceable object of type I. std::output_iterator<I, T> is modeled only if all the concepts it subsumes are modeled, and *i++ = E; has effects equivalent to *i = E; ++i;.

[edit] Equality preservation

Expressions declared in requires expressions of the standard library concepts are required to be equality-preserving (except where stated otherwise).

[edit] Notes

Unlike the LegacyOutputIterator requirements, the output_iterator concept does not require that the iterator category tag be defined.

Algorithms on output iterators should be single pass.

[edit] See also

specifies that objects of a type can be incremented and dereferenced
(concept) [edit]