Hi everybody,
while the partition-by by itself is lazy the subseqs it creates are not
lazy. I was attempting to make that happen. I would like to get comments
from the community about my modification to partition-by so as to make it
create the subsequences in a lazy way ... will this work?
My version :
(defn lazy-partition-by
"Applies f to each value in coll, splitting it each time f returns
a new value. Returns a lazy seq of partitions."
{:added "1.2"}
[f coll]
(lazy-seq
(when-let [s (seq coll)]
(let [fst (first s)
fv (f fst)
run (lazy-seq (cons fst (take-while #(= fv (f %)) (next s))))]
(cons run (lazy-partition-by f (drop-while #(= fv (f %))
s)))))))
original version :
(defn partition-by
"Applies f to each value in coll, splitting it each time f returns
a new value. Returns a lazy seq of partitions."
{:added "1.2"}
[f coll]
(lazy-seq
(when-let [s (seq coll)]
(let [fst (first s)
fv (f fst)
run (cons fst (take-while #(= fv (f %)) (rest s)))]
(cons run (partition-by f (drop (count run) s)))))))
thanks.
Sunil.
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