Hi, I'm doing 4clojure problem 118, and have this so far:

(fn mm [f coll]
   (lazy-seq
    (when (not= [] coll)
      (cons (f (first coll))
            (mm f (rest coll))))))

which works, but it's failing out on the third test

i understand if you are returning a collection, you need to hold onto the head. I'm not sure why this would be so slow, though.

(the error is Execution timed out.)

http://www.4clojure.com/problem/118

@escherize: you might want to look at how to do tail calls with clojure. Have a look at loop & recur.

@escherize if you change (not= [] coll) to (not (empty? coll)) it works. I am not sure why this is.