The only valid use of an
is on the left side of the assignment statement.
Assignment through the same value of the iterator happens only once.
Algorithms on output iterators should never attempt to pass through the same iterator twice.
They should be
Equality and inequality might not be defined.
Algorithms that take output iterators can be used with ostreams as the destination
for placing data through the
class as well as with insert iterators and insert pointers.
— end note