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Instances for Monoidal (,) () #194

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Merged
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Sep 21, 2020
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Instances for Monoidal (,) () #194

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4 changes: 4 additions & 0 deletions src/Data/Profunctor/Kleisli/Linear.hs
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Expand Up @@ -43,6 +43,10 @@ instance Control.Applicative f => Strong Either Void (Kleisli f) where
first (Kleisli f) = Kleisli (either (Data.fmap Left . f) (Control.pure . Right))
second (Kleisli g) = Kleisli (either (Control.pure . Left) (Data.fmap Right . g))

instance Control.Applicative f => Monoidal (,) () (Kleisli f) where
Kleisli f *** Kleisli g = Kleisli $ \(x,y) -> (,) Control.<$> f x Control.<*> g y
unit = Kleisli Control.pure
Comment on lines +47 to +48
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@Divesh-Otwani Divesh-Otwani Sep 18, 2020 •
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Perhaps use -XInstanceSigs and give type signatures for (***) and unit just for readability. It's a bit of a pause figuring out the type in my head. Same for instances below.

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If we are to add instance signatures, we should go over the whole module. So this would be a separate PR.


instance Control.Applicative f => Wandering (Kleisli f) where
wander (Kleisli f) = Kleisli (Data.traverse f)

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11 changes: 11 additions & 0 deletions src/Data/Profunctor/Linear.hs
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Expand Up @@ -80,13 +80,20 @@ instance Strong Either Void LinearArrow where
first (LA f) = LA $ either (Left . f) Right
second (LA g) = LA $ either Left (Right . g)

instance Monoidal (,) () LinearArrow where
LA f *** LA g = LA $ \(a,x) -> (f a, g x)
unit = LA id

instance Profunctor (->) where
dimap f g h x = g (h (f x))
instance Strong (,) () (->) where
first f (x, y) = (f x, y)
instance Strong Either Void (->) where
first f (Left x) = Left (f x)
first _ (Right y) = Right y
instance Monoidal (,) () (->) where
(f *** g) (a,x) = (f a, g x)
unit () = ()

data Exchange a b s t = Exchange (s #-> a) (b #-> t)
instance Profunctor (Exchange a b) where
Expand All @@ -104,6 +111,10 @@ instance Prelude.Applicative f => Strong Either Void (Kleisli f) where
Left x -> Prelude.fmap Left (f x)
Right y -> Prelude.pure (Right y)

instance Prelude.Applicative f => Monoidal (,) () (Kleisli f) where
Kleisli f *** Kleisli g = Kleisli (\(x,y) -> (,) Prelude.<$> f x Prelude.<*> g y)
unit = Kleisli Prelude.pure

data Market a b s t = Market (b #-> t) (s #-> Either t a)
runMarket :: Market a b s t #-> (b #-> t, s #-> Either t a)
runMarket (Market f g) = (f, g)
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