Safe Haskell | None |
---|---|
Language | Haskell2010 |
Synopsis
- data Union (r :: EffectRow) (m :: Type -> Type) a where
- data Yo e m a where
- type Member e r = Member' e r
- weave :: (Functor s, Functor m, Functor n) => s () -> (forall x. s (m x) -> n (s x)) -> (forall x. s x -> Maybe x) -> Union r m a -> Union r n (s a)
- hoist :: (Functor m, Functor n) => (forall x. m x -> n x) -> Union r m a -> Union r n a
- inj :: forall r e a m. (Functor m, Member e r) => e m a -> Union r m a
- weaken :: forall e r m a. 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 -> Type where
- data Nat
- class MemberNoError end r => LastMember end r | r -> end where
- decompLast :: Union r m a -> Either (Union r m a) (Union '[end] m a)
Documentation
data Union (r :: EffectRow) (m :: Type -> Type) 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
.
type Member e r = Member' e r Source #
A proof that the effect e
is available somewhere inside of the effect
stack r
.
weave :: (Functor s, Functor m, Functor n) => s () -> (forall x. s (m x) -> n (s x)) -> (forall x. s x -> Maybe x) -> Union r m a -> Union r n (s a) Source #
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 :: forall e r m a. Union r m a -> Union (e ': r) m a Source #
Weaken a Union
so it is capable of storing a new sort of effect.
Using Unions
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
.
absurdU :: Union '[] m a -> b Source #
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.
Witnesses
data SNat :: Nat -> Type where Source #
A singleton for Nat
.
Instances
TestEquality SNat Source # | |
Defined in Polysemy.Internal.Union |
The kind of type-level natural numbers.
Instances
TestEquality SNat Source # | |
Defined in Polysemy.Internal.Union |
class MemberNoError end r => LastMember end r | r -> end where Source #
A proof that end
is the last effect in the row.
Since: 0.5.0.0
Instances
LastMember end (end ': ([] :: [Effect])) Source # | |
Defined in Polysemy.Internal.Union | |
(LastMember end r, MemberNoError end (eff ': r)) => LastMember end (eff ': r) Source # | |
Defined in Polysemy.Internal.Union |