I've been working on a problem that requires me to write a small state machine for processing XML documents. Out of curiousity (I'm new to functional programming) I hit Google to see how automata are written in other functional languages. I found Shriram Krishnamurthi's paper:
http://lambda-the-ultimate.org/node/569 It is discussed further, along with a Clojure implementation, here: http://list.cs.brown.edu/pipermail/plt-scheme/2007-November/thread.html#21571 The implementation listed there doesn't work, and is before Rich introduced "letfn", so I decided to try my own implementation using letfn and trampoline: (defn machine [start-stream] (letfn [(init [stream] #(cond (empty? stream) true (= \c (first stream)) (more (rest stream)) :else false)) (more [stream] #(cond (empty? stream) true (= \a (first stream)) (more (rest stream)) (= \d (first stream)) (more (rest stream)) (= \r (first stream)) (end (rest stream)) :else false)) (end [stream] #(cond (empty? stream) true :else false))] (trampoline init start-stream))) This works, but if I try to run it on an infinite sequence, it eventually runs out of memory: (machine (iterate (fn [c] (if (= c \c) \a \d)) \c)) Java heap space [Thrown class java.lang.OutOfMemoryError] I don't understand the underlying model of Clojure's runtime well enough to understand why this is occurring. I'm not getting a stack overflow error, so it seems likely that something is holding onto memory (perhaps the entire stream?). Does anyone have any insight into this? Thanks! Charles Gordon -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
