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Add Extend and Comonad instances #15

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Add Extend and Comonad instances #15

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9 changes: 9 additions & 0 deletions src/Data/NonEmpty.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,8 @@ import Prelude

import Control.Alt ((<|>))
import Control.Alternative (class Alternative)
import Control.Comonad (class Comonad)
import Control.Extend (class Extend)
import Control.Plus (class Plus, empty)

import Data.Foldable (class Foldable, foldl, foldr, foldMap)
Expand Down Expand Up @@ -84,6 +86,13 @@ derive instance genericNonEmpty :: (Generic (f a), Generic a) => Generic (NonEmp
instance functorNonEmpty :: Functor f => Functor (NonEmpty f) where
map f (a :| fa) = f a :| map f fa

instance extendNonEmpty :: (Functor f, Plus f) => Extend (NonEmpty f) where
extend f (a :| fa) =
NonEmpty (f (NonEmpty a empty)) (map (\x -> f (NonEmpty x empty)) fa)

instance comonadNonEmpty :: (Functor f, Plus f) => Comonad (NonEmpty f) where
extract (a :| _) = a

instance foldableNonEmpty :: Foldable f => Foldable (NonEmpty f) where
foldMap f (a :| fa) = f a <> foldMap f fa
foldl f b (a :| fa) = foldl f (f b a) fa
Expand Down