Safe Haskell	None
Language	Haskell2010

Polysemy.Internal.Union

Contents

Synopsis

data Union (r :: [(* -> *) -> * -> *]) (m :: * -> *) a where
- Union :: SNat n -> Yo (IndexOf r n) m a -> Union r m a
data Yo e m a where
- Yo :: Functor f => e m a -> f () -> (forall x. f (m x) -> n (f x)) -> (f a -> b) -> Yo e n b
liftYo :: Functor m => e m a -> Yo e m a
type Member e r = Member' e r
inj :: forall r e a m. (Functor m, Member e r) => e m a -> Union r m a
weaken :: Union r m a -> Union (e ': r) m a
decomp :: Union (e ': r) m a -> Either (Union r m a) (Yo e m a)
prj :: forall e r a m. Member e r => Union r m a -> Maybe (Yo e m a)
extract :: Union '[e] m a -> Yo e m a
absurdU :: Union '[] m a -> b
decompCoerce :: Union (e ': r) m a -> Either (Union (f ': r) m a) (Yo e m a)
data SNat :: Nat -> * where
- SZ :: SNat Z
- SS :: Typeable n => SNat n -> SNat (S n)
data Nat
- = Z
- | S Nat

Documentation

data Union (r :: [(* -> *) -> * -> *]) (m :: * -> *) a where Source #

An extensible, type-safe union. The r type parameter is a type-level list of effects, any one of which may be held within the Union.

Constructors

Union
Fields :: SNat n A proof that the effect is actually in `r`. -> Yo (IndexOf r n) m a The effect to wrap. The functions `prj` and `decomp` can help retrieve this value later. -> Union r m a

Instances

Effect (Union r) Source #
Instance details Defined in Polysemy.Internal.Union Methods weave :: (Functor s, Functor m, Functor n) => s () -> (forall x. s (m x) -> n (s x)) -> Union r m a -> Union r n (s a) Source # hoist :: (Functor m, Functor n) => (forall x. m x -> n x) -> Union r m a -> Union r n a Source #
Functor m => Functor (Union r m) Source #
Instance details Defined in Polysemy.Internal.Union Methods fmap :: (a -> b) -> Union r m a -> Union r m b # (<$) :: a -> Union r m b -> Union r m a #

data Yo e m a where Source #

Constructors

Yo :: Functor f => e m a -> f () -> (forall x. f (m x) -> n (f x)) -> (f a -> b) -> Yo e n b

Instances

Effect (Yo e) Source #
Instance details Defined in Polysemy.Internal.Union Methods weave :: (Functor s, Functor m, Functor n) => s () -> (forall x. s (m x) -> n (s x)) -> Yo e m a -> Yo e n (s a) Source # hoist :: (Functor m, Functor n) => (forall x. m x -> n x) -> Yo e m a -> Yo e n a Source #
Functor (Yo e m) Source #
Instance details Defined in Polysemy.Internal.Union Methods fmap :: (a -> b) -> Yo e m a -> Yo e m b # (<$) :: a -> Yo e m b -> Yo e m a #

liftYo :: Functor m => e m a -> Yo e m a Source #

type Member e r = Member' e r Source #

A proof that the effect e is available somewhere inside of the effect stack r.

Building Unions

inj :: forall r e a m. (Functor m, Member e r) => e m a -> Union r m a Source #

Lift an effect e into a Union capable of holding it.

weaken :: Union r m a -> Union (e ': r) m a Source #

Weaken a Union so it is capable of storing a new sort of effect.

decomp :: Union (e ': r) m a -> Either (Union r m a) (Yo e m a) Source #

Decompose a Union. Either this union contains an effect e---the head of the r list---or it doesn't.

prj :: forall e r a m. Member e r => Union r m a -> Maybe (Yo e m a) Source #

Attempt to take an e effect out of a Union.

extract :: Union '[e] m a -> Yo e m a Source #

Retrieve the last effect in a Union.

An empty union contains nothing, so this function is uncallable.

decompCoerce :: Union (e ': r) m a -> Either (Union (f ': r) m a) (Yo e m a) Source #

Like decomp, but allows for a more efficient reinterpret function.

data SNat :: Nat -> * where Source #

A singleton for Nat.

Constructors

SZ :: SNat Z
SS :: Typeable n => SNat n -> SNat (S n)

The kind of type-level natural numbers.

Constructors

Z
S Nat