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From: Matthias Neubauer <neubauer@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Date: 25 Feb 2003 17:01:34 +0100
I, for my part, downloaded the current reference implementation as
found on http://srfi.schemers.org/srfi-40/srfi-40.txt. The only thing
that I then changed was that I replaced the former version of
STREAM-FILTER by the one Phil posted last Thursday. When I load this
into my scsh (0.6.3) and evaluate
(stream-car (stream-filter (lambda (x) (zero? x)) (stream-from 1)))
the whole thing dies pretty soon ejecting a post-gc interrupt---i.e,
scsh seems to run out of memory.
For me, using Scheme 48 version 0.57, the current reference implemenation
leaks for
(stream-car (stream-filter (lambda (x) (zero? x)) (stream-from 1)))
Using either or both the new stream-filter or the non-reentrant promises
fixes the problem.
Our different experiences may be based on differences between the 0.57 and
the Scheme 48 version underlying Scsh 0.6.3. I don't know which version
that is.
The only thing I am not sure about is, if STREAM-UNFOLDN is the right
abstraction to transform streams (it looks a little bit too "heavy
weight" to me ...).
It certainly isn't a polished result. Most of the goofiness comes from
wanting to be able to convert N input streams into M output streams.
It might be simpler to have three functions that handle N->1, 1->1, and
1->N conversions. Perhaps having all four would be the most useful thing
to do.
It's a bit hard to tell what your stream-transform is doing. Can you
explain it? Or give a type?
-Richard Kelsey