On 09/09/13 07:19, Stephen Chang wrote:
Konrad's exactly right. Your filtered-nums blows up because you named the stream and then traversed the entire thing. In general, if you hang onto the head of the stream while traversing then the GC can't collect anything because since you have a pointer to the head, every element of the stream is still reachable.Compare to a common traversal pattern like: (let loop ([s <some stream>]) ... (loop (stream-rest s))) where the head is dropped on each loop iteration. Other comments: - (stream-length (gen-filtered-nums)) is fine because there's no pointer to the head, so the GC collects as you traverse. - in-range is fine because it's constant space and not a cons-cell-based stream. It's more like a generator. - the for/sum is actually collecting while traversing, just more slowly. I'm not exactly sure why, I may look into it. On my machine, it got up to 500mb or so but it finished.
Thanks, and to Konrad too. You're mention of in-range being more like a generator, actually makes me wonder whether a generator would be a better choice for processing large data sets, from databases and csv files, sequentially. What do you think? Lorry -- vLife Systems Ltd Registered Office: The Meridian, 4 Copthall House, Station Square, Coventry, CV1 2FL Registered in England and Wales No. 06477649 http://vlifesystems.com ____________________ Racket Users list: http://lists.racket-lang.org/users
