HI,
Am 10.11.2010 um 21:28 schrieb David Jacobs:
> That is, if I have (1 2 3 4 4 5 5 5 5 5 6 9 12 12), I want to get back
> the sequence (4 4 5 5 5 5 5 12 12).
Low-level solution using lazy-seq. As lazy as possible:
(defn ties
[coll]
(let [step (fn step [seen s]
(lazy-seq
(loop [s (seq s)]
(when-first [fst s]
(if (contains? seen fst)
(cons fst (step seen (rest s)))
(when-let [sn (next s)]
(let [snd (first sn)]
(if (= fst snd)
(cons fst (cons snd (step (conj seen fst)
(rest sn))))
(recur sn)))))))))]
(step #{} coll)))
Sincerely
Meikel
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