Thanks Meikel!
This is a really neat way of writing it, I'm going to need to study this one as
it uses some functions I'm not super familiar with (so thanks very much for
introducing me to them and coming up with this elegant example!).
The only thing is that while your distinct-by function doesn't seem to work...
The nodes are record objects (created via the 'defrecord') and I'm guessing it
has to do with how clojure's "contains?" functions works.
- Greg
On Nov 8, 2010, at 3:24 PM, Meikel Brandmeyer wrote:
> Yeah, golfing at late night..
>
> (defn distinct-by
> [keyfn coll]
> (let [step (fn step [xs seen]
> (lazy-seq
> ((fn [[f :as xs] seen]
> (when-let [s (seq xs)]
> (if (contains? seen (keyfn f))
> (recur (rest s) seen)
> (cons f (step (rest s) (conj seen f))))))
> xs seen)))]
> (step coll #{})))
>
> (defn new-gen
> [a]
> (->> a
> (mapcat (juxt transform-left transform-right))
> (remove (fn [n] (some #(= (:val n) (:val %)) (parents n))))
> (distinct-by :val)))
>
> I modified your distinct to not capture a core name. Also it now exploits
> that seen is a set. Also your contains? is called some.
>
> Hope this helps.
>
> Sincerely
> Meikel
>
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