git.iko.soy/elk
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elk/compiler/src/Data/NonEmptyList.hs
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1module Data.NonEmptyList
2 ( List(..)
3 , singleton
4 , toList
5 , sortBy
6 )
7 where
10import Control.Monad (liftM2)
11import Data.Binary (Binary, get, put)
12import qualified Data.List as List
16-- LIST
19data List a =
20 List a [a]
23singleton :: a -> List a
24singleton a =
25 List a []
28toList :: List a -> [a]
29toList (List x xs) =
30 x:xs
34-- INSTANCES
37instance Functor List where
38 fmap func (List x xs) = List (func x) (map func xs)
41instance Traversable List where
42 traverse func (List x xs) = List <$> func x <*> traverse func xs
45instance Foldable List where
46 foldr step state (List x xs) = step x (foldr step state xs)
47 foldl step state (List x xs) = foldl step (step state x) xs
48 foldl1 step (List x xs) = foldl step x xs
52-- SORT BY
55sortBy :: (Ord b) => (a -> b) -> List a -> List a
56sortBy toRank (List x xs) =
57 let
58 comparison a b =
59 compare (toRank a) (toRank b)
60 in
61 case List.sortBy comparison xs of
62 [] ->
63 List x []
65 y:ys ->
66 case comparison x y of
67 LT -> List x (y:ys)
68 EQ -> List x (y:ys)
69 GT -> List y (List.insertBy comparison x ys)
73-- BINARY
76instance (Binary a) => Binary (List a) where
77 put (List x xs) = put x >> put xs
78 get = liftM2 List get get