Moduleprofunctors-5.6.3Haskell2010

Data.Profunctor.Composition

2 types
11 values

Packageprofunctors-5.6.3
Exports13
LanguageHaskell2010
LicenceBSD-3-Clause
SourceComposition.hs

Profunctor Composition

2 declarations

datadata Procompose (p :: k -> k1 -> Type) (q :: k2 -> k -> Type) (d :: k2) (c :: k1) where

Procompose p q is the Profunctor composition of the Profunctors p and q.

For a good explanation of Profunctor composition in Haskell see Dan Piponi's article:

http://blog.sigfpe.com/2011/07/profunctors-in-haskell.html

Procompose has a polymorphic kind since 5.6.

Constructors

Procompose :: p x c -> q d x -> Procompose p q d c

Instances17ProfunctorFunctor, ProfunctorMonad, ProfunctorAdjunction, Choice, Closed, Mapping, …

ProfunctorFunctor (Procompose p)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
Category p => ProfunctorMonad (Procompose p)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
ProfunctorAdjunction (Procompose p) (Rift p)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Choice p, Choice q) => Choice (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Closed p, Closed q) => Closed (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Mapping p, Mapping q) => Mapping (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Corepresentable p, Corepresentable q) => Costrong (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Strong p, Strong q) => Strong (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Profunctor p, Profunctor q) => Profunctor (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Traversing p, Traversing q) => Traversing (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Corepresentable p, Corepresentable q) => Corepresentable (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Representable p, Representable q) => Representable (Procompose p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
The composition of two Representable Profunctors is Representable by the composition of their representations.
(Cosieve p f, Cosieve q g) => Cosieve (Procompose p q) (Compose f g)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Sieve p f, Sieve q g) => Sieve (Procompose p q) (Compose g f)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
Profunctor p => Functor (Procompose p q a)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
type Corep (Procompose p q) = Compose (Corep p) (Corep q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
type Rep (Procompose p q) = Compose (Rep q) (Rep p)Defined in profunctors-5.6.3 · Data.Profunctor.Composition

valueprocomposed :: Category p => Procompose p p a b -> p a b

Unitors and Associator

3 declarations

valueidl :: Profunctor q => Iso (Procompose (->) q d c) (Procompose (->) r d' c') (q d c) (r d' c')

(->) functions as a lax identity for Profunctor composition.

This provides an Iso for the lens package that witnesses the isomorphism between Procompose (->) q d c and q d c, which is the left identity law.

idl :: Profunctor q => Iso' (Procompose (->) q d c) (q d c)

valueidr :: Profunctor q => Iso (Procompose q (->) d c) (Procompose r (->) d' c') (q d c) (r d' c')

(->) functions as a lax identity for Profunctor composition.

This provides an Iso for the lens package that witnesses the isomorphism between Procompose q (->) d c and q d c, which is the right identity law.

idr :: Profunctor q => Iso' (Procompose q (->) d c) (q d c)

valueassoc

:: (Profunctor p2, Functor f)
=> p2 (Procompose (Procompose p1 q) r a b) (f (Procompose (Procompose x y) z a b))
-> p2 (Procompose p1 (Procompose q r) a b) (f (Procompose x (Procompose y z) a b))

The associator for Profunctor composition.

This provides an Iso for the lens package that witnesses the isomorphism between Procompose p (Procompose q r) a b and Procompose (Procompose p q) r a b, which arises because Prof is only a bicategory, rather than a strict 2-category.

Categories as monoid objects

2 declarations

valueeta :: (Profunctor p, Category p) => (->) :-> p

a Category that is also a Profunctor is a Monoid in Prof

valuemu :: Category p => Procompose p p :-> p

Generalized Composition

4 declarations

value

stars :: Functor g => Iso (Procompose (Star f) (Star g) d c) (Procompose (Star f') (Star g') d' c') (Star (Compose g f) d c) (Star (Compose g' f') d' c')

Profunctor composition generalizes Functor composition in two ways.

This is the first, which shows that exists b. (a -> f b, b -> g c) is isomorphic to a -> f (g c).

stars :: Functor f => Iso' (Procompose (Star f) (Star g) d c) (Star (Compose f g) d c)

value

kleislis :: Monad g => Iso (Procompose (Kleisli f) (Kleisli g) d c) (Procompose (Kleisli f') (Kleisli g') d' c') (Kleisli (Compose g f) d c) (Kleisli (Compose g' f') d' c')

This is a variant on stars that uses Kleisli instead of Star.

kleislis :: Monad f => Iso' (Procompose (Kleisli f) (Kleisli g) d c) (Kleisli (Compose f g) d c)

value

costars :: Functor f => Iso (Procompose (Costar f) (Costar g) d c) (Procompose (Costar f') (Costar g') d' c') (Costar (Compose f g) d c) (Costar (Compose f' g') d' c')

Profunctor composition generalizes Functor composition in two ways.

This is the second, which shows that exists b. (f a -> b, g b -> c) is isomorphic to g (f a) -> c.

costars :: Functor f => Iso' (Procompose (Costar f) (Costar g) d c) (Costar (Compose g f) d c)

value

cokleislis :: Functor f => Iso (Procompose (Cokleisli f) (Cokleisli g) d c) (Procompose (Cokleisli f') (Cokleisli g') d' c') (Cokleisli (Compose f g) d c) (Cokleisli (Compose f' g') d' c')

This is a variant on costars that uses Cokleisli instead of Costar.

cokleislis :: Functor f => Iso' (Procompose (Cokleisli f) (Cokleisli g) d c) (Cokleisli (Compose g f) d c)

Right Kan Lift

2 declarations

newtypenewtype Rift (p :: k -> k1 -> Type) (q :: k2 -> k1 -> Type) (a :: k2) (b :: k)

This represents the right Kan lift of a Profunctor q along a Profunctor p in a limited version of the 2-category of Profunctors where the only object is the category Hask, 1-morphisms are profunctors composed and compose with Profunctor composition, and 2-morphisms are just natural transformations.

Rift has a polymorphic kind since 5.6.

Constructors

Rift
- runRift :: forall (x :: k1). p b x -> q a x

Instances6ProfunctorFunctor, Category, ProfunctorComonad, ProfunctorAdjunction, Profunctor, Functor

ProfunctorFunctor (Rift p)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
p ~ q => Category (Rift p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
Rift p p forms a Monad in the Profunctor 2-category, which is isomorphic to a Haskell Category instance.
Category p => ProfunctorComonad (Rift p)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
ProfunctorAdjunction (Procompose p) (Rift p)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
(Profunctor p, Profunctor q) => Profunctor (Rift p q)Defined in profunctors-5.6.3 · Data.Profunctor.Composition
Profunctor p => Functor (Rift p q a)Defined in profunctors-5.6.3 · Data.Profunctor.Composition

valuedecomposeRift :: Procompose p (Rift p q) a b -> q a b

The 2-morphism that defines a left Kan lift.

Note: When p is right adjoint to Rift p (->) then decomposeRift is the counit of the adjunction.