23 Iterators library [iterators]

23.3 Iterator requirements [iterator.requirements]

23.3.5 C++17 iterator requirements [iterator.cpp17]

23.3.5.4 Output iterators [output.iterators]

A class or pointer type X meets the requirements of an output iterator if X meets the Cpp17Iterator requirements ([iterator.iterators]) and the expressions in Table 90 are valid and have the indicated semantics.
Table 90: Cpp17OutputIterator requirements (in addition to Cpp17Iterator) [tab:outputiterator]
Expression
Return type
Operational
Assertion/note
semantics
pre-/post-condition
*r = o
result is not used
Remarks: After this operation r is not required to be dereferenceable.

Postconditions: r is incrementable.
++r
X&
addressof(r) == addressof(++r).

Remarks: After this operation r is not required to be dereferenceable.

Postconditions: r is incrementable.
r++
convertible to const X&
{ X tmp = r;
++r;
return tmp; }
Remarks: After this operation r is not required to be dereferenceable.

Postconditions: r is incrementable.
*r++ = o
result is not used
Remarks: After this operation r is not required to be dereferenceable.

Postconditions: r is incrementable.
Recommended practice: The implementation of an algorithm on output iterators should never attempt to pass through the same iterator twice; such an algorithm should be a single-pass algorithm.
[Note 1:
The only valid use of an operator* is on the left side of the assignment statement.
Assignment through the same value of the iterator happens only once.
Equality and inequality are not necessarily defined.
— end note]