Hi,
On 3 Apr., 12:24, Ken Wesson <kwess...@gmail.com> wrote:
> I don't. :)
>
> (defn drop-by [f coll]
> (let [fs (map f coll)
> ps (map = fs (rest fs))
> zs (map list ps (rest coll))]
> (map second (drop-while first zs))))
>
> user=> (drop-by #(mod % 3) [1 4 1 7 34 16 10 2 99 103 42])
> (2 99 103 42)
>
> I especially like the symmetry of using take-while for the one and
> drop-while for the other, under the hood.
Or a bit less involved.
(defn take-by
[f coll]
(lazy-seq
(when-let [s (seq coll)]
(let [fst (first s)
value (f fst)]
(cons fst (take-while #(-> % f (= value)) (rest s)))))))
(defn drop-by
[f coll]
(lazy-seq
(when-let [s (seq coll)]
(let [fst (first s)
value (f fst)]
(drop-while #(-> % f (= value)) (rest s))))))
Sincerely
Meikel
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