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Adds FunctorWithIndex instance to Cofree #118

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Merged
merged 2 commits into from
Sep 27, 2021
Merged

Adds FunctorWithIndex instance to Cofree #118

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70bb226
Adds FunctorWithIndex instance to Cofree
Sep 19, 2021
b9dbb12
Updates change log
Sep 27, 2021
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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -8,6 +8,8 @@ Breaking changes:

New features:

- Added a `FunctorWithIndex` instance for `Cofree` (#118 by @mikesol)

Bugfixes:

Other improvements:
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6 changes: 6 additions & 0 deletions src/Control/Comonad/Cofree.purs
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Expand Up @@ -22,6 +22,7 @@ import Control.Monad.Free (Free, runFreeM)
import Control.Monad.Rec.Class (class MonadRec)
import Control.Monad.State (State, StateT(..), runState, runStateT, state)
import Data.Eq (class Eq1, eq1)
import Data.FunctorWithIndex (class FunctorWithIndex)
import Data.Foldable (class Foldable, foldr, foldl, foldMap)
import Data.Lazy (Lazy, force, defer)
import Data.Ord (class Ord1, compare1)
Expand Down Expand Up @@ -145,6 +146,11 @@ instance functorCofree :: Functor f => Functor (Cofree f) where
where
loop (Cofree fa) = Cofree ((\(Tuple a b) -> Tuple (f a) (loop <$> b)) <$> fa)

instance functorWithIndexCofree :: Functor f => FunctorWithIndex Int (Cofree f) where
mapWithIndex f = loop 0
where
loop n (Cofree fa) = Cofree ((\(Tuple a b) -> Tuple (f n a) (loop (n + 1) <$> b)) <$> fa)

instance foldableCofree :: Foldable f => Foldable (Cofree f) where
foldr f = flip go
where
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