**Paste:**#108632**Author(s):**1HaskellADay**Language:**Haskell**Channel:**-**Created:**2014-08-02 14:54:35 UTC**Revisions:**- 2014-08-02 18:57:27 UTC #108651 (diff): No title (1HaskellADay)
- 2014-08-02 18:00:09 UTC #108641 (diff): No title (1HaskellADay)
- 2014-08-02 16:25:33 UTC #108635 (diff): No title (1HaskellADay)
- 2014-08-02 14:56:03 UTC #108633 (diff): No title (1HaskellADay)
- 2014-08-02 14:54:35 UTC #108632: Master of the Universe (1HaskellADay)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | module Data.Universe where import Control.Comonad -- http://lpaste.net/107661 {-- The Universe data type (not from logic) of universal extent to the left and right; perfect for cellular automata http://lpaste.net/108632 So, fun fact: the fifty-zillion best seller "50 Shades of Grey(er)(est)" was originally Twilight fan-fiction (submissive Bella meets smoky-eyed Dom Edward, in case you missed the obvious parallels) written under the pen name of, and I'm not joking here, 'Master of the Universe.' I mention this in passing. So. An universe is a type of universal extent to the left and to the right: --} data U a = U [a] a [a] right :: U a -> U a right (U a b (c:cs)) = U (b:a) c cs left :: U a -> U a left (U (a:as) b c) = U as a (b:c) instance Functor U where fmap f (U a b c) = U (map f a) (f b) (map f c) instance Copointed U where extract (U _ b _) = b instance Comonad U where duplicate a = U (tail $ iterate left a) a (tail $ iterate right a) shift :: Int -> U a -> U a shift i u = (iterate (if i < 0 then left else right) u) !! abs i toList :: Int -> Int -> U a -> [a] toList i j u = take (j-i) $ half $ shift i u where half (U _ b c) = b:c instance Show a => Show (U a) where show univ = "U " ++ show (toList (-10) 20 univ) showCompact :: Show a => U a -> Int -> String showCompact univ haWidth = "U " ++ concatMap show (toList (negate haWidth) (2 * haWidth) univ) {-- (Debt of gratitude to sigfpe for the type from his article on Comonadic cellular automata. http://blog.sigfpe.com/2006/12/evaluating-cellular-automata-is.html) This type is used for, e.g. modelling cellular automata, particularly the rules for generation of the same. See: http://lpaste.net/107206 And there you have it! An Universe, just for you! So don't tell me I never did anything for you, eh? --} |

39:13: Warning: Redundant bracket

Found:

(iterate (if i < 0 then left else right) u) !! abs i

Why not:

iterate (if i < 0 then left else right) u !! abs i