It's been quite a while, and I've had a single +1 on this with very
little comment. Does anyone else have an opinion? Is anyone opposed?
Does anyone think `cycleN n` should produce a *result* of length `n`
instead of cycling `n` times? I seek advice and consent of anyone who
cares.
On Wed, Mar 11, 2015 at 11:14 AM, David Feuer
Yesterday I rewrote `*>` for Data.Sequence (again), using an internal function
cycleN :: Int -> Seq a -> Seq a
The name of the function is based on that of Data.Sequence.iterateN. cycleN takes a sequence and cycles it as many times as requested:
cycleN 0 $ fromList [1,2] = [] cycleN 5 $ fromList [1,2] = [1,2,1,2,1,2,1,2,1,2]
The function is written to maximize sharing in the result sequence and to minimize construction time. Specifically, cycleN n xs should take something like O(|xs| + log n) space (of which all but O(log |xs| + log n) is shared with the structure of xs) and O(log |xs| + log n) time.
With current (on GitHub) Data.Sequence exports, the only way to get this functionality with these time and space bounds is to combine replicate with *> :
cycleN n xs = replicate n () *> xs
This strikes me as a bit unpleasant.
David