# 99 questions/Solutions/15

### From HaskellWiki

< 99 questions | Solutions(Difference between revisions)

(added solution using list monad) |
(Added an alternative and more verbose solution) |

## Revision as of 05:11, 10 August 2011

(**) 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 (n-1)