Moduleeffectful-core-2.7.1.2GHC2021

Effectful.Reader.Static

Support for access to a read only value of a particular type.

Note: strictly speaking the value is not read only because of local. If you want to ensure that the initial value never changes, use Effectful.Input.Static.

1 type
5 values

Packageeffectful-core-2.7.1.2
Exports6
LanguageGHC2021
LicenceBSD-3-Clause
SourceStatic.hs

Effect

1 declaration

datadata Reader r (a :: Type -> Type) b

Provide access to a strict (WHNF), thread local, read only value of type r.

Instances2DispatchOf, StaticRep

type DispatchOf (Reader r) = 'Static 'NoSideEffectsDefined in effectful-core-2.7.1.2 · Effectful.Reader.Static
data StaticRep (Reader r)
- Reader r
Defined in effectful-core-2.7.1.2 · Effectful.Reader.Static

Handlers

valuerunReader

:: HasCallStack
=> r
The initial environment.
-> Eff (Reader r ': es) a
-> Eff es a

Run a Reader effect with the given initial environment.

valuewithReader

:: HasCallStack
=> (r1 -> r2)
The function to modify the environment.
-> Eff (Reader r2 ': es) a
Computation to run in the modified environment.
-> Eff (Reader r1 ': es) a

Execute a computation in a modified environment.

Operations

valueask :: (HasCallStack, Reader r :> es) => Eff es r

Fetch the value of the environment.

valueasks

:: (HasCallStack, Reader r :> es)
=> (r -> a)
The function to apply to the environment.
-> Eff es a

Retrieve a function of the current environment.

asks f ≡ f <$> ask

valuelocal

:: (HasCallStack, Reader r :> es)
=> (r -> r)
The function to modify the environment.
-> Eff es a
-> Eff es a

Execute a computation in a modified environment.

runReader r (local f m) ≡ runReader (f r) m