module Itertools (
  flatmap,
  windows
  ) where

windows :: Int -> [a] -> [[a]]
windows _ [] = []
windows i (x:xs)
  | length xs < i-1 = []
  | otherwise = (x:take (i-1) xs):windows i xs

flatmap :: (t -> [a]) -> [t] -> [a]
flatmap _ []     = []
flatmap f (x:xs) = f x ++ flatmap f xs