Safe Haskell	None
Language	Haskell2010

Control.Effect.Reader

Synopsis

data Reader r :: Effect where
- Ask :: Reader r m r
- Local :: (r1 -> r2) -> Eff (Reader r2 ': effs) a -> Reader r1 (Eff effs) a
ask :: Reader r :< effs => Eff effs r
local :: Reader r1 :< effs => (r1 -> r2) -> Eff (Reader r2 ': effs) a -> Eff effs a
runReader :: r -> Eff (Reader r ': effs) a -> Eff effs a

Documentation

The Reader r effect provides access to a global environment of type r.

Handlers should obey the law f <$> ask ≡ local f ask.

Constructors

Ask :: Reader r m r
Local :: (r1 -> r2) -> Eff (Reader r2 ': effs) a -> Reader r1 (Eff effs) a

ask :: Reader r :< effs => Eff effs r Source #

Retrieves a value from the environment.

local :: Reader r1 :< effs => (r1 -> r2) -> Eff (Reader r2 ': effs) a -> Eff effs a Source #

Runs a subcomputation in an environment modified by the given function.

runReader :: r -> Eff (Reader r ': effs) a -> Eff effs a Source #

Handles a Reader effect by supplying a value for the environment.