Copyright	(c) Fumiaki Kinoshita 2019
License	BSD3
Maintainer	Fumiaki Kinoshita <fumiexcel@gmail.com>
Stability	stable
Portability	non-portable
Safe Haskell	None
Language	Haskell2010

Data.Witherable.Class

Description

Synopsis

class Functor f => Filterable f where
- mapMaybe :: (a -> Maybe b) -> f a -> f b
- catMaybes :: f (Maybe a) -> f a
- filter :: (a -> Bool) -> f a -> f a
class (Traversable t, Filterable t) => Witherable t where
- wither :: Applicative f => (a -> f (Maybe b)) -> t a -> f (t b)
- witherM :: Monad m => (a -> m (Maybe b)) -> t a -> m (t b)
- filterA :: Applicative f => (a -> f Bool) -> t a -> f (t a)

Documentation

class Functor f => Filterable f where Source #

Like Functor, but you can remove elements instead of updating them.

Formally, the class Filterable represents a functor from Kleisli Maybe to Hask.

A definition of mapMaybe must satisfy the following laws:

conservation: mapMaybe (Just . f) ≡ fmap f
composition: mapMaybe f . mapMaybe g ≡ mapMaybe (f <=< g)

Minimal complete definition

mapMaybe | catMaybes

Methods

mapMaybe :: (a -> Maybe b) -> f a -> f b Source #

Like mapMaybe.

catMaybes :: f (Maybe a) -> f a Source #

catMaybes ≡ mapMaybe id

filter :: (a -> Bool) -> f a -> f a Source #

filter f . filter g ≡ filter (liftA2 (&&) f g)

Instances

Filterable [] Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> [a] -> [b] Source # catMaybes :: [Maybe a] -> [a] Source # filter :: (a -> Bool) -> [a] -> [a] Source #
Filterable Maybe Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Maybe a -> Maybe b Source # catMaybes :: Maybe (Maybe a) -> Maybe a Source # filter :: (a -> Bool) -> Maybe a -> Maybe a Source #
Filterable Option Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Option a -> Option b Source # catMaybes :: Option (Maybe a) -> Option a Source # filter :: (a -> Bool) -> Option a -> Option a Source #
Filterable ZipList Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> ZipList a -> ZipList b Source # catMaybes :: ZipList (Maybe a) -> ZipList a Source # filter :: (a -> Bool) -> ZipList a -> ZipList a Source #
Filterable IntMap Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> IntMap a -> IntMap b Source # catMaybes :: IntMap (Maybe a) -> IntMap a Source # filter :: (a -> Bool) -> IntMap a -> IntMap a Source #
Filterable Seq Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Seq a -> Seq b Source # catMaybes :: Seq (Maybe a) -> Seq a Source # filter :: (a -> Bool) -> Seq a -> Seq a Source #
Filterable Vector Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Vector a -> Vector b Source # catMaybes :: Vector (Maybe a) -> Vector a Source # filter :: (a -> Bool) -> Vector a -> Vector a Source #
Monoid e => Filterable (Either e) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Either e a -> Either e b Source # catMaybes :: Either e (Maybe a) -> Either e a Source # filter :: (a -> Bool) -> Either e a -> Either e a Source #
Filterable (V1 :: Type -> Type) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> V1 a -> V1 b Source # catMaybes :: V1 (Maybe a) -> V1 a Source # filter :: (a -> Bool) -> V1 a -> V1 a Source #
Filterable (U1 :: Type -> Type) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> U1 a -> U1 b Source # catMaybes :: U1 (Maybe a) -> U1 a Source # filter :: (a -> Bool) -> U1 a -> U1 a Source #
Filterable (Proxy :: Type -> Type) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Proxy a -> Proxy b Source # catMaybes :: Proxy (Maybe a) -> Proxy a Source # filter :: (a -> Bool) -> Proxy a -> Proxy a Source #
Filterable (Map k) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Map k a -> Map k b Source # catMaybes :: Map k (Maybe a) -> Map k a Source # filter :: (a -> Bool) -> Map k a -> Map k a Source #
Functor f => Filterable (MaybeT f) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> MaybeT f a -> MaybeT f b Source # catMaybes :: MaybeT f (Maybe a) -> MaybeT f a Source # filter :: (a -> Bool) -> MaybeT f a -> MaybeT f a Source #
(Eq k, Hashable k) => Filterable (HashMap k) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> HashMap k a -> HashMap k b Source # catMaybes :: HashMap k (Maybe a) -> HashMap k a Source # filter :: (a -> Bool) -> HashMap k a -> HashMap k a Source #
Filterable f => Filterable (Rec1 f) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Rec1 f a -> Rec1 f b Source # catMaybes :: Rec1 f (Maybe a) -> Rec1 f a Source # filter :: (a -> Bool) -> Rec1 f a -> Rec1 f a Source #
Filterable (Const r :: Type -> Type) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Const r a -> Const r b Source # catMaybes :: Const r (Maybe a) -> Const r a Source # filter :: (a -> Bool) -> Const r a -> Const r a Source #
Filterable t => Filterable (Reverse t) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Reverse t a -> Reverse t b Source # catMaybes :: Reverse t (Maybe a) -> Reverse t a Source # filter :: (a -> Bool) -> Reverse t a -> Reverse t a Source #
Filterable f => Filterable (IdentityT f) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> IdentityT f a -> IdentityT f b Source # catMaybes :: IdentityT f (Maybe a) -> IdentityT f a Source # filter :: (a -> Bool) -> IdentityT f a -> IdentityT f a Source #
Filterable t => Filterable (Backwards t) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Backwards t a -> Backwards t b Source # catMaybes :: Backwards t (Maybe a) -> Backwards t a Source # filter :: (a -> Bool) -> Backwards t a -> Backwards t a Source #
(Filterable f, Filterable g) => Filterable (f :+: g) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> (f :+: g) a -> (f :+: g) b Source # catMaybes :: (f :+: g) (Maybe a) -> (f :+: g) a Source # filter :: (a -> Bool) -> (f :+: g) a -> (f :+: g) a Source #
(Filterable f, Filterable g) => Filterable (f :*: g) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> (f :: g) a -> (f :: g) b Source # catMaybes :: (f :: g) (Maybe a) -> (f :: g) a Source # filter :: (a -> Bool) -> (f :: g) a -> (f :: g) a Source #
(Filterable f, Filterable g) => Filterable (Product f g) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Product f g a -> Product f g b Source # catMaybes :: Product f g (Maybe a) -> Product f g a Source # filter :: (a -> Bool) -> Product f g a -> Product f g a Source #
(Filterable f, Filterable g) => Filterable (Sum f g) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Sum f g a -> Sum f g b Source # catMaybes :: Sum f g (Maybe a) -> Sum f g a Source # filter :: (a -> Bool) -> Sum f g a -> Sum f g a Source #
Filterable f => Filterable (M1 i c f) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> M1 i c f a -> M1 i c f b Source # catMaybes :: M1 i c f (Maybe a) -> M1 i c f a Source # filter :: (a -> Bool) -> M1 i c f a -> M1 i c f a Source #
(Functor f, Filterable g) => Filterable (f :.: g) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> (f :.: g) a -> (f :.: g) b Source # catMaybes :: (f :.: g) (Maybe a) -> (f :.: g) a Source # filter :: (a -> Bool) -> (f :.: g) a -> (f :.: g) a Source #
(Functor f, Filterable g) => Filterable (Compose f g) Source #
Instance details Defined in Data.Witherable.Class Methods mapMaybe :: (a -> Maybe b) -> Compose f g a -> Compose f g b Source # catMaybes :: Compose f g (Maybe a) -> Compose f g a Source # filter :: (a -> Bool) -> Compose f g a -> Compose f g a Source #

class (Traversable t, Filterable t) => Witherable t where Source #

An enhancement of Traversable with Filterable

A definition of wither must satisfy the following laws:

conservation: wither (fmap Just . f) ≡ traverse f
composition: Compose . fmap (wither f) . wither g ≡ wither (Compose . fmap (wither f) . g)

Parametricity implies the naturality law:

t . wither f ≡ wither (t . f)

Minimal complete definition

Nothing

Methods

wither :: Applicative f => (a -> f (Maybe b)) -> t a -> f (t b) Source #

Effectful mapMaybe.

wither (pure . f) ≡ pure . mapMaybe f

witherM :: Monad m => (a -> m (Maybe b)) -> t a -> m (t b) Source #

Monadic variant of wither. This may have more efficient implementation.

filterA :: Applicative f => (a -> f Bool) -> t a -> f (t a) Source #

Instances

Witherable [] Source #	Methods are good consumers for fusion.
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> [a] -> f [b] Source # witherM :: Monad m => (a -> m (Maybe b)) -> [a] -> m [b] Source # filterA :: Applicative f => (a -> f Bool) -> [a] -> f [a] Source #
Witherable Maybe Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Maybe a -> f (Maybe b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Maybe a -> m (Maybe b) Source # filterA :: Applicative f => (a -> f Bool) -> Maybe a -> f (Maybe a) Source #
Witherable Option Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Option a -> f (Option b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Option a -> m (Option b) Source # filterA :: Applicative f => (a -> f Bool) -> Option a -> f (Option a) Source #
Witherable ZipList Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> ZipList a -> f (ZipList b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> ZipList a -> m (ZipList b) Source # filterA :: Applicative f => (a -> f Bool) -> ZipList a -> f (ZipList a) Source #
Witherable IntMap Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> IntMap a -> f (IntMap b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> IntMap a -> m (IntMap b) Source # filterA :: Applicative f => (a -> f Bool) -> IntMap a -> f (IntMap a) Source #
Witherable Seq Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Seq a -> f (Seq b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Seq a -> m (Seq b) Source # filterA :: Applicative f => (a -> f Bool) -> Seq a -> f (Seq a) Source #
Witherable Vector Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Vector a -> f (Vector b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Vector a -> m (Vector b) Source # filterA :: Applicative f => (a -> f Bool) -> Vector a -> f (Vector a) Source #
Monoid e => Witherable (Either e) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Either e a -> f (Either e b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Either e a -> m (Either e b) Source # filterA :: Applicative f => (a -> f Bool) -> Either e a -> f (Either e a) Source #
Witherable (V1 :: Type -> Type) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> V1 a -> f (V1 b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> V1 a -> m (V1 b) Source # filterA :: Applicative f => (a -> f Bool) -> V1 a -> f (V1 a) Source #
Witherable (U1 :: Type -> Type) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> U1 a -> f (U1 b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> U1 a -> m (U1 b) Source # filterA :: Applicative f => (a -> f Bool) -> U1 a -> f (U1 a) Source #
Witherable (Proxy :: Type -> Type) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Proxy a -> f (Proxy b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Proxy a -> m (Proxy b) Source # filterA :: Applicative f => (a -> f Bool) -> Proxy a -> f (Proxy a) Source #
Witherable (Map k) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Map k a -> f (Map k b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Map k a -> m (Map k b) Source # filterA :: Applicative f => (a -> f Bool) -> Map k a -> f (Map k a) Source #
Traversable t => Witherable (MaybeT t) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> MaybeT t a -> f (MaybeT t b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> MaybeT t a -> m (MaybeT t b) Source # filterA :: Applicative f => (a -> f Bool) -> MaybeT t a -> f (MaybeT t a) Source #
(Eq k, Hashable k) => Witherable (HashMap k) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> HashMap k a -> f (HashMap k b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> HashMap k a -> m (HashMap k b) Source # filterA :: Applicative f => (a -> f Bool) -> HashMap k a -> f (HashMap k a) Source #
Witherable f => Witherable (Rec1 f) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> Rec1 f a -> f0 (Rec1 f b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Rec1 f a -> m (Rec1 f b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> Rec1 f a -> f0 (Rec1 f a) Source #
Witherable (Const r :: Type -> Type) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Const r a -> f (Const r b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Const r a -> m (Const r b) Source # filterA :: Applicative f => (a -> f Bool) -> Const r a -> f (Const r a) Source #
Witherable t => Witherable (Reverse t) Source #	Wither from right to left.
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Reverse t a -> f (Reverse t b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Reverse t a -> m (Reverse t b) Source # filterA :: Applicative f => (a -> f Bool) -> Reverse t a -> f (Reverse t a) Source #
Witherable f => Witherable (IdentityT f) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> IdentityT f a -> f0 (IdentityT f b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> IdentityT f a -> m (IdentityT f b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> IdentityT f a -> f0 (IdentityT f a) Source #
Witherable t => Witherable (Backwards t) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f => (a -> f (Maybe b)) -> Backwards t a -> f (Backwards t b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Backwards t a -> m (Backwards t b) Source # filterA :: Applicative f => (a -> f Bool) -> Backwards t a -> f (Backwards t a) Source #
(Witherable f, Witherable g) => Witherable (f :+: g) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> (f :+: g) a -> f0 ((f :+: g) b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> (f :+: g) a -> m ((f :+: g) b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> (f :+: g) a -> f0 ((f :+: g) a) Source #
(Witherable f, Witherable g) => Witherable (f :*: g) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> (f :: g) a -> f0 ((f :: g) b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> (f :: g) a -> m ((f :: g) b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> (f :: g) a -> f0 ((f :: g) a) Source #
(Witherable f, Witherable g) => Witherable (Product f g) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> Product f g a -> f0 (Product f g b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Product f g a -> m (Product f g b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> Product f g a -> f0 (Product f g a) Source #
(Witherable f, Witherable g) => Witherable (Sum f g) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> Sum f g a -> f0 (Sum f g b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Sum f g a -> m (Sum f g b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> Sum f g a -> f0 (Sum f g a) Source #
Witherable f => Witherable (M1 i c f) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> M1 i c f a -> f0 (M1 i c f b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> M1 i c f a -> m (M1 i c f b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> M1 i c f a -> f0 (M1 i c f a) Source #
(Traversable f, Witherable g) => Witherable (f :.: g) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> (f :.: g) a -> f0 ((f :.: g) b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> (f :.: g) a -> m ((f :.: g) b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> (f :.: g) a -> f0 ((f :.: g) a) Source #
(Traversable f, Witherable g) => Witherable (Compose f g) Source #
Instance details Defined in Data.Witherable.Class Methods wither :: Applicative f0 => (a -> f0 (Maybe b)) -> Compose f g a -> f0 (Compose f g b) Source # witherM :: Monad m => (a -> m (Maybe b)) -> Compose f g a -> m (Compose f g b) Source # filterA :: Applicative f0 => (a -> f0 Bool) -> Compose f g a -> f0 (Compose f g a) Source #