Sha256: 1a1845abdf7540bf7c025fdad1d93296e41a0c056187ad54cc858e88e69991a4
Contents?: true
Size: 540 Bytes
Versions: 236
Compression:
Stored size: 540 Bytes
Contents
module PascalsTriangle
(rows
) where
import Prelude
import Data.Array (drop, zip, (:))
import Data.Maybe (Maybe(..))
import Data.Tuple (uncurry)
type Row = Array Int
type Mat = Array (Array Int)
rows' :: Row -> Int -> Mat
rows' row 1 = [row]
rows' row n = row : rows' next (n - 1)
where next = pairSum $ [0] <> row <> [0]
pairSum r = map (uncurry (+)) (zip r (drop 1 r))
rows :: Maybe Int -> Maybe Mat
rows Nothing = Nothing
rows (Just n)
| n < 0 = Nothing
| n == 0 = Just []
| otherwise = Just $ rows' [1] n
Version data entries
236 entries across 236 versions & 1 rubygems