99 questions/Solutions/15
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m (Improved my version a little) 

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Revision as of 16:55, 19 November 2012
(**) Replicate the elements of a list a given number of times.
repli :: [a] > Int > [a] repli xs n = concatMap (replicate n) xs
or, in Pointfree style:
repli = flip $ concatMap . replicate
replicate
repli :: [a] > Int > [a] repli xs n = concatMap (take n . repeat) xs
or, using the list monad:
repli :: [a] > Int > [a] repli xs n = xs >>= replicate n
replicate
repli :: [a] > Int > [a] repli xs n = foldl (\acc e > acc ++ repli' e n) [] xs where repli' _ 0 = [] repli' x n = x : repli' x (n1)
or, a version that does not use list concatenation:
repli :: [a] > Int > [a] repli [] _ = [] repli (x:xs) n = foldr (const (x:)) (repli xs n) [1..n]