Copyright	2013-2016 Edward Kmett and Dan Doel
License	BSD
Maintainer	Edward Kmett <ekmett@gmail.com>
Stability	experimental
Portability	rank N types
Safe Haskell	None
Language	Haskell98

Data.Functor.Day.Curried

Contents

Right Kan lifts

Description

Day f -| Curried f

Day f ~ Compose f when f preserves colimits / is a left adjoint. (Due in part to the strength of all functors in Hask.)

So by the uniqueness of adjoints, when f is a left adjoint, Curried f ~ Rift f

Synopsis

Right Kan lifts

newtype Curried g h a Source

Constructors

Curried
Fields runCurried :: forall r. g (a -> r) -> h r

Instances

Functor g => Functor (Curried g h) Source
(Functor g, (~) (* -> *) g h) => Applicative (Curried g h) Source

toCurried :: (forall x. Day g k x -> h x) -> k a -> Curried g h a Source

The universal property of Curried

fromCurried :: Functor f => (forall a. k a -> Curried f h a) -> Day f k b -> h b Source

toCurried . fromCurried ≡ id
fromCurried . toCurried ≡ id

applied :: Functor f => Day f (Curried f g) a -> g a Source

This is the counit of the Day f -| Curried f adjunction

unapplied :: g a -> Curried f (Day f g) a Source

This is the unit of the Day f -| Curried f adjunction

adjointToCurried :: Adjunction f u => u a -> Curried f Identity a Source

Curried f Identity a is isomorphic to the right adjoint to f if one exists.

adjointToCurried . curriedToAdjoint ≡ id
curriedToAdjoint . adjointToCurried ≡ id

curriedToAdjoint :: Adjunction f u => Curried f Identity a -> u a Source

Curried f Identity a is isomorphic to the right adjoint to f if one exists.

composedAdjointToCurried :: (Functor h, Adjunction f u) => u (h a) -> Curried f h a Source

Curried f h a is isomorphic to the post-composition of the right adjoint of f onto h if such a right adjoint exists.

curriedToComposedAdjoint :: Adjunction f u => Curried f h a -> u (h a) Source

Curried f h a is isomorphic to the post-composition of the right adjoint of f onto h if such a right adjoint exists.

curriedToComposedAdjoint . composedAdjointToCurried ≡ id
composedAdjointToCurried . curriedToComposedAdjoint ≡ id

liftCurried :: Applicative f => f a -> Curried f f a Source

The natural isomorphism between f and Curried f f. lowerCurried . liftCurried ≡ id liftCurried . lowerCurried ≡ id

lowerCurried (liftCurried x)     -- definition
lowerCurried (Curried (<*> x))   -- definition
(<*> x) (pure id)          -- beta reduction
pure id <*> x              -- Applicative identity law
x

lowerCurried :: Applicative f => Curried f g a -> g a Source

Lower Curried by applying pure id to the continuation.

See liftCurried.

rap :: Functor f => Curried f g (a -> b) -> Curried g h a -> Curried f h b Source

Indexed applicative composition of right Kan lifts.