diff options
Diffstat (limited to 'libraries/base/Data/Traversable.hs')
| -rw-r--r-- | libraries/base/Data/Traversable.hs | 61 |
1 files changed, 54 insertions, 7 deletions
diff --git a/libraries/base/Data/Traversable.hs b/libraries/base/Data/Traversable.hs index 5c2745edeb..93c42258e2 100644 --- a/libraries/base/Data/Traversable.hs +++ b/libraries/base/Data/Traversable.hs @@ -60,11 +60,13 @@ import Data.Foldable ( Foldable ) import Data.Functor import Data.Functor.Identity ( Identity(..) ) import Data.Functor.Utils ( StateL(..), StateR(..) ) -import Data.Monoid ( Dual(..), Sum(..), Product(..), First(..), Last(..) ) +import Data.Monoid ( Dual(..), Sum(..), Product(..), + First(..), Last(..), Alt(..), Ap(..) ) +import Data.Ord ( Down(..) ) import Data.Proxy ( Proxy(..) ) import GHC.Arr -import GHC.Base ( Applicative(..), Monad(..), Monoid, Maybe(..), +import GHC.Base ( Applicative(..), Monad(..), Monoid, Maybe(..), NonEmpty(..), ($), (.), id, flip ) import GHC.Generics import qualified GHC.List as List ( foldr ) @@ -163,7 +165,7 @@ class (Functor t, Foldable t) => Traversable t where traverse f = sequenceA . fmap f -- | Evaluate each action in the structure from left to right, and - -- and collect the results. For a version that ignores the results + -- collect the results. For a version that ignores the results -- see 'Data.Foldable.sequenceA_'. sequenceA :: Applicative f => t (f a) -> f (t a) {-# INLINE sequenceA #-} -- See Note [Inline default methods] @@ -198,8 +200,8 @@ Consider This gives rise to a list-instance of mapM looking like this - $fTraversable[]_$ctaverse = ...code for traverse on lists... - {-# INLINE $fTraversable[]_$ctaverse #-} + $fTraversable[]_$ctraverse = ...code for traverse on lists... + {-# INLINE $fTraversable[]_$ctraverse #-} $fTraversable[]_$cmapM = $fTraversable[]_$ctraverse Now the $ctraverse obediently inlines into the RHS of $cmapM, /but/ @@ -237,6 +239,10 @@ instance Traversable [] where traverse f = List.foldr cons_f (pure []) where cons_f x ys = liftA2 (:) (f x) ys +-- | @since 4.9.0.0 +instance Traversable NonEmpty where + traverse f ~(a :| as) = liftA2 (:|) (f a) (traverse f as) + -- | @since 4.7.0.0 instance Traversable (Either a) where traverse _ (Left x) = pure (Left x) @@ -285,12 +291,22 @@ instance Traversable First where instance Traversable Last where traverse f (Last x) = Last <$> traverse f x +-- | @since 4.12.0.0 +instance (Traversable f) => Traversable (Alt f) where + traverse f (Alt x) = Alt <$> traverse f x + +-- | @since 4.12.0.0 +instance (Traversable f) => Traversable (Ap f) where + traverse f (Ap x) = Ap <$> traverse f x + -- | @since 4.9.0.0 instance Traversable ZipList where traverse f (ZipList x) = ZipList <$> traverse f x +-- | @since 4.9.0.0 deriving instance Traversable Identity + -- Instances for GHC.Generics -- | @since 4.9.0.0 instance Traversable U1 where @@ -303,21 +319,52 @@ instance Traversable U1 where sequence _ = pure U1 {-# INLINE sequence #-} +-- | @since 4.9.0.0 deriving instance Traversable V1 + +-- | @since 4.9.0.0 deriving instance Traversable Par1 + +-- | @since 4.9.0.0 deriving instance Traversable f => Traversable (Rec1 f) + +-- | @since 4.9.0.0 deriving instance Traversable (K1 i c) + +-- | @since 4.9.0.0 deriving instance Traversable f => Traversable (M1 i c f) + +-- | @since 4.9.0.0 deriving instance (Traversable f, Traversable g) => Traversable (f :+: g) + +-- | @since 4.9.0.0 deriving instance (Traversable f, Traversable g) => Traversable (f :*: g) + +-- | @since 4.9.0.0 deriving instance (Traversable f, Traversable g) => Traversable (f :.: g) + +-- | @since 4.9.0.0 deriving instance Traversable UAddr + +-- | @since 4.9.0.0 deriving instance Traversable UChar + +-- | @since 4.9.0.0 deriving instance Traversable UDouble + +-- | @since 4.9.0.0 deriving instance Traversable UFloat + +-- | @since 4.9.0.0 deriving instance Traversable UInt + +-- | @since 4.9.0.0 deriving instance Traversable UWord +-- Instance for Data.Ord +-- | @since 4.12.0.0 +deriving instance Traversable Down + -- general functions -- | 'for' is 'traverse' with its arguments flipped. For a version @@ -333,14 +380,14 @@ forM :: (Traversable t, Monad m) => t a -> (a -> m b) -> m (t b) forM = flip mapM -- |The 'mapAccumL' function behaves like a combination of 'fmap' --- and 'foldl'; it applies a function to each element of a structure, +-- and 'Data.Foldable.foldl'; it applies a function to each element of a structure, -- passing an accumulating parameter from left to right, and returning -- a final value of this accumulator together with the new structure. mapAccumL :: Traversable t => (a -> b -> (a, c)) -> a -> t b -> (a, t c) mapAccumL f s t = runStateL (traverse (StateL . flip f) t) s -- |The 'mapAccumR' function behaves like a combination of 'fmap' --- and 'foldr'; it applies a function to each element of a structure, +-- and 'Data.Foldable.foldr'; it applies a function to each element of a structure, -- passing an accumulating parameter from right to left, and returning -- a final value of this accumulator together with the new structure. mapAccumR :: Traversable t => (a -> b -> (a, c)) -> a -> t b -> (a, t c) |