Data.Coyoneda

data CoyonedaF f a i

Coyoneda is encoded as an existential type using Data.Exists.

This type constructor encodes the contents of the existential package.

newtype Coyoneda f a

The Coyoneda Functor.

Coyoneda f is a Functor for any type constructor f. In fact, it is the free Functor for f.

Constructors

• Coyoneda (Exists (CoyonedaF f a))

Instances

• (Functor f, Eq1 f, Eq a) => Eq (Coyoneda f a)
• (Functor f, Eq1 f) => Eq1 (Coyoneda f)
• (Functor f, Ord1 f, Ord a) => Ord (Coyoneda f a)
• (Functor f, Ord1 f) => Ord1 (Coyoneda f)
• Functor (Coyoneda f)
• (Apply f) => Apply (Coyoneda f)
• (Applicative f) => Applicative (Coyoneda f)
• (Bind f) => Bind (Coyoneda f)
• (Monad f) => Monad (Coyoneda f)
• MonadTrans Coyoneda
• (Extend w) => Extend (Coyoneda w)
• (Comonad w) => Comonad (Coyoneda w)

coyoneda :: forall b a f. (a -> b) -> f a -> Coyoneda f b

Construct a value of type Coyoneda f b from a mapping function and a value of type f a.

unCoyoneda :: forall a g f. (forall b. (b -> a) -> f b -> g a) -> Coyoneda f a -> g a

Deconstruct a value of Coyoneda a to retrieve the mapping function and original value.

liftCoyoneda :: forall f. f ~> (Coyoneda f)

Lift a value described by the type constructor f to Coyoneda f.

lowerCoyoneda :: forall f. Functor f => (Coyoneda f) ~> f

Lower a value of type Coyoneda f a to the Functor f.

hoistCoyoneda :: forall g f. (f ~> g) -> (Coyoneda f) ~> (Coyoneda g)

Use a natural transformation to change the generating type constructor of a Coyoneda.