euler_008.hs

partitionAll :: Int -> Int -> [a] -> [[a]]
partitionAll _ _ [] = []
partitionAll w s xs = (take w xs) : partitionAll w s (drop s xs)

largestProductInSeries :: Int -> [Int] -> Int
largestProductInSeries l xs = maximum $ map (product) $ partitionAll l 1 xs

main = do
  f <- readFile "008.txt"
  let s = filter isDigit f
  let xs = map (read . (:"")) s :: [Int]
  print $ largestProductInSeries 13 xs