Lens.Family.Stock

This module contains lenses and traversals for common structures in Haskell. It also contains the combinators for lenses and traversals.

Lens Combinators

choosing :: Functor f => LensLike f a a' c c' -> LensLike f b b' c c' -> LensLike f (Either a b) (Either a' b') c c'

choosing :: Lens a a' c c' -> Lens b b' c c' -> Lens (Either a b) (Either a' b') c c'

choosing :: Traversal a a' c c' -> Traversal b b' c c' -> Traversal (Either a b) (Either a' b') c c'

choosing :: Getter a a' c c' -> Getter b b' c c' -> Getter (Either a b) (Either a' b') c c'

choosing :: Fold a a' c c' -> Fold b b' c c' -> Fold (Either a b) (Either a' b') c c'

choosing :: Setter a a' c c' -> Setter b b' c c' -> Setter (Either a b) (Either a' b') c c'

Given two lens/traversal/getter/fold/setter families with the same substructure, make a new lens/traversal/getter/fold/setter on Either.

alongside :: Functor f => LensLike (AlongsideLeft f b2') a1 a1' b1 b1' -> LensLike (AlongsideRight f a1') a2 a2' b2 b2' -> LensLike f (a1, a2) (a1', a2') (b1, b2) (b1', b2')

alongside :: Lens a1 a1' b1 b1' -> Lens a2 a2' b2 b2' -> Lens (a1, a2) (a1', a2') (b1, b2) (b1', b2')

alongside :: Getter a1 a1' b1 b1' -> Getter a2 a2' b2 b2' -> Getter (a1, a2) (a1', a2') (b1, b2) (b1', b2')

Given two lens/getter families, make a new lens/getter on their product.

beside :: Applicative f => LensLike f a a' c c' -> LensLike f b b' c c' -> LensLike f (a, b) (a', b') c c'

beside :: Traversal a a' c c' -> Traversal b' b' c c' -> Traversal (a,b) (a',b') c c'

beside :: Fold a a' c c' -> Fold b' b' c c' -> Fold (a,b) (a',b') c c'

beside :: Setter a a' c c' -> Setter b' b' c c' -> Setter (a,b) (a',b') c c'

Given two traversals/folds/setters referencing a type c, create a traversal/fold/setter on the pair referencing c.

Stock Lenses

_1 :: Functor f => LensLike f (a, b) (a', b) a a'

_1 :: Lens (a, b) (a', b) a a'

Lens on the first element of a pair.

_2 :: Functor f => LensLike f (a, b) (a, b') b b'

_2 :: Lens (a, b) (a, b') b b'

Lens on the second element of a pair.

chosen :: Functor f => LensLike f (Either a a) (Either b b) a b

chosen :: Lens (Either a a) (Either b b) a b

Lens on the Left or Right element of an (Either a a).

ix :: (Eq k, Functor f) => k -> LensLike' f (k -> v) v

ix :: Eq k => k -> Lens' (k -> v) v

Lens on a given point of a function.

at :: (Ord k, Functor f) => k -> LensLike' f (Map k v) (Maybe v)

at :: Ord k => k -> Lens' (Map.Map k v) (Maybe v)

Lens on a given point of a Map.

intAt :: Functor f => Int -> LensLike' f (IntMap v) (Maybe v)

intAt :: Int -> Lens (IntMap.IntMap v) (Maybe v)

Lens on a given point of a IntMap.

contains :: (Ord k, Functor f) => k -> LensLike' f (Set k) Bool

contains :: Ord => k -> Lens' (Set.Set k) Bool

Lens on a given point of a Set.

intContains :: Functor f => Int -> LensLike' f IntSet Bool

intContains :: Int -> Lens' IntSet.IntSet Bool

Lens on a given point of a IntSet.

Stock Traversals

both :: Applicative f => LensLike f (a, a) (b, b) a b

both :: Traversal (a,a) (b,b) a b

Traversals on both elements of a pair (a,a).

_Left :: Applicative f => LensLike f (Either a b) (Either a' b) a a'

_Left :: Traversal (Either a b) (Either a' b) a a'

Traversal on the Left element of an Either.

_Right :: Applicative f => LensLike f (Either a b) (Either a b') b b'

_Right :: Traversal (Either a b) (Either a b') b b'

Traversal on the Right element of an Either.

_Just :: Applicative f => LensLike f (Maybe a) (Maybe a') a a'

_Just :: Traversal (Maybe a) (Maybe a') a a'

Traversal on the Just element of a Maybe.

_Nothing :: Applicative f => LensLike' f (Maybe a) ()

_Nothing :: Traversal' (Maybe a) ()

Traversal on the Nothing element of a Maybe.

ignored :: Applicative f => null -> a -> f a

ignored :: Traversal a a b b'

The empty traversal on any type.

Stock SECs

mapped :: (Identical f, Functor g) => LensLike f (g a) (g a') a a'

mapped :: Functor g => Setter (g a) (g a') a a'

An SEC referencing the parameter of a functor.

Types

data AlongsideLeft f b a

Instances

Functor f => Functor (AlongsideLeft f a)

Phantom f => Phantom (AlongsideLeft f a)

data AlongsideRight f a b

Instances

Functor f => Functor (AlongsideRight f a)

Phantom f => Phantom (AlongsideRight f a)

Re-exports

type LensLike f a a' b b' = (b -> f b') -> a -> f a'

type LensLike' f a b = (b -> f b) -> a -> f a

class Functor f => Applicative f

A functor with application, providing operations to

• embed pure expressions (pure), and
• sequence computations and combine their results (<*>).

A minimal complete definition must include implementations of these functions satisfying the following laws:

identity

pure id <*> v = v

composition

pure (.) <*> u <*> v <*> w = u <*> (v <*> w)

homomorphism

pure f <*> pure x = pure (f x)

interchange

u <*> pure y = pure ($ y) <*> u

The other methods have the following default definitions, which may be overridden with equivalent specialized implementations:

• u *> v = pure (const id) <*> u <*> v

• u <* v = pure const <*> u <*> v

As a consequence of these laws, the Functor instance for f will satisfy

• fmap f x = pure f <*> x

If f is also a Monad, it should satisfy

• pure = return

• (<*>) = ap

(which implies that pure and <*> satisfy the applicative functor laws).

Minimal complete definition

pure, (<*>)

Instances

Applicative []

Applicative IO

Applicative ZipList

Applicative STM

Applicative ReadPrec

Applicative ReadP

Applicative Maybe

Applicative Identity

Applicative ((->) a)

Applicative (Either e)

Monoid a => Applicative ((,) a)

Applicative (ST s)

Monoid m => Applicative (Const m)

Monad m => Applicative (WrappedMonad m)

Applicative (ST s)

Arrow a => Applicative (ArrowMonad a)

Applicative (Proxy *)

Applicative f => Applicative (Backwards f)

Apply f-actions in the reverse order.

Monoid a => Applicative (Constant a)

Arrow a => Applicative (WrappedArrow a b)

(Monoid w, Applicative m) => Applicative (WriterT w m)

(Functor m, Monad m) => Applicative (StateT s m)

(Functor m, Monad m) => Applicative (StateT s m)

(Applicative f, Applicative g) => Applicative (Compose f g)

(Monoid c, Monad m) => Applicative (Zooming m c)

Applicative (IKleeneStore b b')

Typeable ((* -> *) -> Constraint) Applicative

class Applicative f => Identical f

Minimal complete definition

extract

Instances

Identical Identity

Identical f => Identical (Backwards f)

(Identical f, Identical g) => Identical (Compose f g)