+1, `cycleN` is Data.Sequence's corollary of `cycle` in Data.List
On Wed, Mar 11, 2015 at 8:14 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 _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
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