Last active
August 29, 2016 20:18
-
-
Save jamesthompson/82eaf75567c85df0c56fabeaa58f4f9c to your computer and use it in GitHub Desktop.
Triangle 0 1 printing with comonadic stream
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| import Control.Comonad (extract, (<<=), (=>>)) | |
| import Control.Monad (void) | |
| import Data.Functor (fmap) | |
| import Data.List (intersperse) | |
| import Data.List.NonEmpty (NonEmpty, toList, (<|)) | |
| import Data.Monoid (mconcat) | |
| import Data.Traversable (traverse) | |
| import Prelude (IO, Int, String, drop, id, mod, otherwise, | |
| putStrLn, take, undefined, ($), (.), (==)) | |
| triangleIO :: Int -> IO () | |
| triangleIO count = | |
| void $ traverse putStrLn $ take count triangle' | |
| triangle :: String | |
| triangle = mconcat $ intersperse "\n" triangle' | |
| triangle' :: [String] | |
| triangle' = fmap h [1..] | |
| where f n | n `mod` 2 == 0 = g '0' '1' | |
| | otherwise = g '1' '0' | |
| g x y = x <| y <| g x y =>> extract | |
| h n = intersperse ' ' . take n . toList $ f n |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment