Add Functor-, Foldable-, and TraversableWithIndex instances to EnvT

CHANGELOG.md

@@ -7,6 +7,7 @@ Notable changes to this project are documented in this file. The format is based
 Breaking changes:
 
 New features:
+- Add `Foldable`, `FoldableWithIndex`, and `Traversable` instances for `EnvT` (#113 by @abaco)
 
 Bugfixes:
 

src/Control/Comonad/Env/Trans.purs

@@ -8,7 +8,10 @@ import Control.Comonad (class Comonad, extract)
 import Control.Comonad.Trans.Class (class ComonadTrans)
 import Control.Extend (class Extend, (<<=))
 
+import Data.FoldableWithIndex (class FoldableWithIndex, foldrWithIndex, foldlWithIndex, foldMapWithIndex)
+import Data.FunctorWithIndex (class FunctorWithIndex, mapWithIndex)
 import Data.Traversable (class Traversable, class Foldable, foldl, foldr, foldMap, traverse, sequence)
+import Data.TraversableWithIndex (class TraversableWithIndex, traverseWithIndex)
 import Data.Tuple (Tuple(..))
 import Data.Newtype (class Newtype)
 
@@ -55,3 +58,14 @@ instance foldableEnvT :: Foldable f => Foldable (EnvT e f) where
 instance traversableEnvT :: Traversable f => Traversable (EnvT e f) where
   sequence (EnvT (Tuple a x)) = EnvT <$> Tuple a <$> sequence x
   traverse f (EnvT (Tuple a x)) = EnvT <$> Tuple a <$> traverse f x
+
+instance functorWithIndexEnvT :: FunctorWithIndex i w => FunctorWithIndex i (EnvT e w) where
+  mapWithIndex f (EnvT (Tuple e x)) = EnvT $ Tuple e (mapWithIndex f x)
+
+instance foldableWithIndexEnvT :: FoldableWithIndex i w => FoldableWithIndex i (EnvT e w) where
+  foldlWithIndex f a (EnvT (Tuple _ x)) = foldlWithIndex f a x
+  foldrWithIndex f a (EnvT (Tuple _ x)) = foldrWithIndex f a x
+  foldMapWithIndex f (EnvT (Tuple _ x)) = foldMapWithIndex f x
+
+instance traversableWithIndexEnvT :: TraversableWithIndex i w => TraversableWithIndex i (EnvT e w) where
+  traverseWithIndex f (EnvT (Tuple e x)) = EnvT <$> Tuple e <$> traverseWithIndex f x