MatchingSub.hs

{-- | List the sub-sequences of conscutives elements in the list such that the
    sum of the element is equal to the given number.

    Examples:

    >>> matchingSub 10 [1..5]
    [[1,2,3,4]]

    >>> matchingSub 2 $ replicate 3 1
    [[1,1],[1,1]]

    >>> take 2 $ matchingSub 2 $ repeat 1
    [[1,1],[1,1]]
--}

import Data.Maybe(mapMaybe)
import Data.List(find, inits, tails)

matchingSub :: Int -> [Int] -> [[Int]]
matchingSub n = mapMaybe (find match . inits) . tails
 where
  match xs' = sum xs' == n

main :: IO ()
main = do
  print $ matchingSub 10 [1..5]
  print $ matchingSub 2 $ replicate 3 1
  print $ take 2 $ matchingSub 2 $ repeat 1