On Sat, Aug 7, 2010 at 9:36 PM, gary ng <garyng2...@gmail.com> wrote:
> if you don't mind about performance, this seems to be natural to me
>
> user=> (reverse (map reverse (reduce (fn [a e] (if (even? e) (cons [e] a)
> (cons
> (cons e (first a)) (rest a)))) (list) [1 2 3 7 5 4 1])))
> ((1) (2 3 7 5) (4 1))
I reworked that a bit, to parameterize it:
(defn pw [f? x]
(let [phi (fn [a e]
(if (f? e)
(cons [e] a)
(cons (cons e (first a))
(rest a))))]
(reverse
(map reverse
(reduce phi () x)))))
This is in the same family as my version 2, but I think it is much
cleaner. This approach gets rid of the recursion, a definite win.
Thanks, Gary.
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