func over the elements of
That is to say,
func will be called as
user_data) for each object in
this. The normal use of this procedure is to accumulate the results of operating on the objects in
The fold will proceed as long as
true. When the iterator has no more arguments,
DONE will be returned. If
, the fold will stop, and OK will be returned. Errors or
resyncs will cause fold to return ERROR or
RESYNC as appropriate.
The iterator will not be freed.
The Iterator to fold over
the fold function
the seed value passed to the fold function
user data passed to the fold function