Re: Running out of memory when using filter?

[Stephen C. Gilardi]

I think I finally see the problem. The "rest expression" in filter's call to lazy-cons has a reference to "coll" in it. That's all it takes for coll to be retained during the entire calculation of the rest.

(defn filter
  "Returns a lazy seq of the items in coll for which
  (pred item) returns true. pred must be free of side-effects."
  [pred coll]
    (when (seq coll)
      (if (pred (first coll))
        (lazy-cons (first coll) (filter pred (rest coll)))
        (recur pred (rest coll)))))



Posting so someone else can beat me to the answer. :-)

--Steve

The stye of fix that occurs to me involves peeling off coll from (frest coll) and (rrest coll) before continuing the lazy evaluation.

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