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[Python-Dev] Re: Reiterability

Andrew Koenig ark-mlist at att.net
Wed Oct 22 09:24:15 EDT 2003 
> I thought we already established before that attempting to guess wihch
> parts of a generator function to copy and which parts to share is
> hopeless.  generator-made iterators won't be __copy__-able, period.

> I think this is the weakness of this cloning business, because it
> either makes generators second-class iterators, or it makes cloning a
> precarious thing to attempt when generators are used.  (You can make a
> non-cloneable iterator cloneable by wrapping it into something that
> buffers just those items that are still reacheable by clones, but this
> can still require arbitrary amounts of buffer space.

However, the buffering can be done in a way that uses only as much buffer
space as is truly needed.  Just maintain the buffer as a singly linked list
in which new elements are inserted at the *tail* of the list.  Then whenever
the head becomes unreachable (e.g. because no iterators refer to it), it
will be garbage collected.
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