;; Does anyone know what the hell is going on here ? (clojure-version) "1.5.1" ;; I mean, this is bad enough: ;; Here's a function to sum up all the numbers from 1..n (def gauss-recurse (fn [n] (if (< n 1) 0 (+ n (gauss-recurse (dec n)))))) (gauss-recurse 3500) ;-> 6126750 (gauss-recurse 4000) ;-> StackOverflowError clojure.lang.Numbers$LongOps.combine (Numbers.java:394) ;; A maximum stack depth of 3500 or so is completely rubbish, but it's been like that for a while. ;; But I don't remember this: (def gauss-memoized (memoize (fn [n] (if (< n 1) 0 (+ n (gauss-memoized (dec n))))))) (gauss-memoized 160) ;-> StackOverflowError clojure.lang.RT.boundedLength (RT.java:1654) (gauss-memoized 100) ;-> 5050 I could probably do this in my head. At least it's the right answer. ;; Why would memoization affect the stack depth anyway? ;; Please please let this be a bug, or some idiocy on my part. ;; Please don't let my favourite language have decided that I can't ;; memoize a recursive function for any non-trivial problem. ;; And if any smartarse is thinking: 'You could use' (reduce + (range 1 5001)) ;-> 12502500 (* 5000 5001 1/2) ;-> 12502500N ;; or (defn gauss-tail ([n] (gauss-tail n 0)) ([n acc] (if (zero? n) acc (recur (dec n) (+ n acc))))) (gauss-tail 5000) ;-> 12502500 ;; etc, etc, etc, then I already know, ok. That's not the point. So fuck off. ;; Unless you're about to give me a general macro which will transform ;; any collection of mutually recursive functions into an efficient ;; stackless implementation which avoids repeated solutions of the ;; same problem. In which case I will be most interested. ;; How on earth do you program without recursion ? ;; And why would you want to?
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