| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Control.Effect.Internal.Union
Synopsis
- type Effect = (Type -> Type) -> Type -> Type
- data Union (r :: [Effect]) m a where
- type Algebra r m = forall x. Union r m x -> m x
- type Algebra' r m a = Union r m a -> m a
- class (forall m n x. Coercible m n => Coercible (e m x) (e n x)) => RepresentationalEff (e :: Effect)
- decomp :: RepresentationalEff e => Union (e ': r) m a -> Either (Union r m a) (e m a)
- extract :: RepresentationalEff e => Union '[e] m a -> e m a
- weaken :: Union r m a -> Union (e ': r) m a
- absurdU :: Union '[] m a -> b
- weakenAlg :: Algebra' (e ': r) m a -> Algebra' r m a
- powerAlg :: forall e r m a. RepresentationalEff e => Algebra' r m a -> (e m a -> m a) -> Algebra' (e ': r) m a
- powerAlg' :: forall e r m a. Algebra' r m a -> (forall z. Coercible z m => e z a -> m a) -> Algebra' (e ': r) m a
- addPrim :: forall e r p m z a. Monad z => Reformulation' r p m z a -> Reformulation' (e ': r) (e ': p) m z a
- liftReform :: (MonadTrans t, Monad m) => Reformulation' r p m z a -> Reformulation' r p (t m) z a
- coerceReform :: Coercible m n => Reformulation' r p m z a -> Reformulation' r p n z a
- weakenReform :: Reformulation' (e ': r) p m z a -> Reformulation' r p m z a
- type Reformulation' r p m z a = (forall x. m x -> z x) -> Algebra p z -> Algebra' r z a
- type Reformulation r p m = forall z. Monad z => (forall x. m x -> z x) -> Algebra p z -> Algebra r z
- class RepresentationalEff e => ThreadsEff t e where
- class Threads t p where
- inj :: Member e r => e m a -> Union r m a
- class (forall i. Threads (ReaderT i) p) => ReaderThreads p
- coerceEff :: forall n m e a. (Coercible n m, RepresentationalEff e) => e m a -> e n a
- coerceAlg :: forall n m e a b. (Coercible n m, RepresentationalEff e) => (e m a -> m b) -> e n a -> n b
- data Bundle :: [Effect] -> Effect
- type family Append l r where ...
- type family FlattenBundles (e :: [Effect]) :: [Effect] where ...
- type family Members (es :: [Effect]) (r :: [Effect]) :: Constraint where ...
- type EffMembers (xs :: [Effect]) (r :: [Effect]) = Members (FlattenBundles xs) r
Documentation
type Effect = (Type -> Type) -> Type -> Type Source #
The kind of effects.
Helpful for defining new effects:
data InOut i o :: Effect where Input :: InOut i o m i Output :: o -> InOut i o m ()
data Union (r :: [Effect]) m a where Source #
An effect for collecting multiple effects into one effect.
Behind the scenes, Union is the most important effect
in the entire library, as the Carrier class is built
around handling Unions of effects.
However, even outside of defining novel Carrier instances,
Union can be useful as an effect in its own right.
Union is useful for effect newtypes -- effects defined through creating a
newtype over an existing effect.
By making a newtype of Union, it's possible to wrap multiple effects in one
newtype.
Not to be confused with Bundle.
Unlike Bundle, Union is a proper effect that is given no
special treatment by Eff or Effs.
type Algebra r m = forall x. Union r m x -> m x Source #
An Algebra r mm over
all effects in the list r.
type Algebra' r m a = Union r m a -> m a Source #
A first-rank type which can often be used instead of Algebra
class (forall m n x. Coercible m n => Coercible (e m x) (e n x)) => RepresentationalEff (e :: Effect) Source #
RepresentationalEff is the constraint every effect is expected
to satisfy: namely, that any effect e m a is representational in m,
which -- in practice -- means that no constraints are ever placed upon
m within the definion of e, and that m isn't present in
the return type of any action of e.
You don't need to make instances of RepresentationalEff; the compiler
will automatically infer if your effect satisfies it.
RepresentationalEff is not a very serious requirement, and
even effects that don't satisfy it can typically be rewritten into
equally powerful variants that do.
If you ever encounter that an effect you've written doesn't satisfy
RepresentationalEff, please consult
the wiki.
Instances
| (forall (m :: Type -> Type) (n :: Type -> Type) x. Coercible m n => Coercible (e m x) (e n x)) => RepresentationalEff e Source # | |
Defined in Control.Effect.Internal.Union | |
extract :: RepresentationalEff e => Union '[e] m a -> e m a Source #
Extract the only effect of an Union.
weakenAlg :: Algebra' (e ': r) m a -> Algebra' r m a Source #
Weaken an Algebra by removing the topmost effect.
powerAlg :: forall e r m a. RepresentationalEff e => Algebra' r m a -> (e m a -> m a) -> Algebra' (e ': r) m a Source #
Strengthen an Algebra by providing a handler for a new effect e.
powerAlg' :: forall e r m a. Algebra' r m a -> (forall z. Coercible z m => e z a -> m a) -> Algebra' (e ': r) m a Source #
addPrim :: forall e r p m z a. Monad z => Reformulation' r p m z a -> Reformulation' (e ': r) (e ': p) m z a Source #
Add a primitive effect and corresponding derived effect to a Reformulation.
liftReform :: (MonadTrans t, Monad m) => Reformulation' r p m z a -> Reformulation' r p (t m) z a Source #
Lift an m-based Reformulation to a t m-based Reformulation,
where t is any MonadTrans
coerceReform :: Coercible m n => Reformulation' r p m z a -> Reformulation' r p n z a Source #
weakenReform :: Reformulation' (e ': r) p m z a -> Reformulation' r p m z a Source #
Weaken a Reformulation by removing the topmost
derived effect.
type Reformulation' r p m z a = (forall x. m x -> z x) -> Algebra p z -> Algebra' r z a Source #
A less higher-rank variant of Reformulation, which is sometimes
important.
type Reformulation r p m = forall z. Monad z => (forall x. m x -> z x) -> Algebra p z -> Algebra r z Source #
The type of reformulate.
A Reformulation r p mr are
formulated in terms of the primitive effects p and first-order operations
of m.
This is done by providing an Algebra r zz that lifts
m and implements an Algebra over p.
class RepresentationalEff e => ThreadsEff t e where Source #
An instance of ThreadsEff represents the ability for a monad transformer
t to thread a primitive effect e -- i.e. lift handlers of that effect.
Instances of ThreadsEff are accumulated into entire stacks of primitive
effects by Threads.
You only need to make ThreadsEff instances for monad transformers that
aren't simply newtypes over existing monad transformers. You also don't need
to make them for IdentityT.
Instances
class Threads t p where Source #
Threads t pThreadsEff t ee in p. By using the Threads t pAlgebras over p from any monad m to t m. This is useful
when defining custom Carrier instances.
Note that you should not place a Threads t pt is
simply a newtype over an existsing monad transformer u that already has
ThreadsEff instances defined for it. Instead, you should place a
Threads u pthread by coercing the resulting
algebra from Algebra p (u m)Algebra p (t m)ThreadsEff instances for
every newtype of a monad transformer.
Threads forms the basis of threading constraints
(see Threaders), and every threading constraint offered
in the library makes use of Threads in one way or another.
inj :: Member e r => e m a -> Union r m a Source #
Inject an effect into a Union containing that effect.
class (forall i. Threads (ReaderT i) p) => ReaderThreads p Source #
The most common threading constraint of the library, as it is emitted by
-Simple interpreters (interpreters that internally make use of
interpretSimple or reinterpretSimple).
ReaderThreads accepts all the primitive effects
(intended to be used as such) offered in this library.
Most notably, ReaderThreads accepts Unlift b
Instances
| (forall i. Threads (ReaderT i) p) => ReaderThreads p Source # | |
Defined in Control.Effect.Internal.Union | |
coerceEff :: forall n m e a. (Coercible n m, RepresentationalEff e) => e m a -> e n a Source #
coerceAlg :: forall n m e a b. (Coercible n m, RepresentationalEff e) => (e m a -> m b) -> e n a -> n b Source #
data Bundle :: [Effect] -> Effect Source #
A pseudo-effect given special treatment by Eff
and Effs.
An Eff/sBundle '[eff1, eff2, ... , effn]eff1 through effn.
For example:
Errore =Bundle'[Throwe,Catche]
so
Eff(Errore) m = (Carrierm,Member(Throwe) (Derivsm),Member(Catche) (Derivsm))
Bundle should never be used in any other contexts but within
Eff and Effs, as it isn't an actual effect.
Not to be confused with Union, which is a proper
effect that combines multiple effects into one.
type family FlattenBundles (e :: [Effect]) :: [Effect] where ... Source #
Equations
| FlattenBundles '[] = '[] | |
| FlattenBundles (Bundle bs ': es) = Append (FlattenBundles bs) (FlattenBundles es) | |
| FlattenBundles (e ': es) = e ': FlattenBundles es |
type EffMembers (xs :: [Effect]) (r :: [Effect]) = Members (FlattenBundles xs) r Source #