Safe Haskell	Safe-Inferred
Language	Haskell2010

Bluefin.StateSource

Contents

Handle
Handlers
Effectful operations

Synopsis

data StateSource (st :: Effects)
withStateSource :: forall (es :: Effects) a. (forall (e :: Effects). StateSource e -> Eff (e :& es) a) -> Eff es a
newState :: forall (e :: Effects) s (es :: Effects). StateSource e -> s -> Eff es (State s e)

Documentation

A StateSource allows you to allocate new State handles, much like ST allows you to allocate new STRefs. This can be useful when you want to avoid nested runState (or evalState blocks), or you need an only dynamically known number of mutable states.

Handle

data StateSource (st :: Effects) #

Handle to a capability to create strict mutable state handles

Handlers

withStateSource #

Arguments

:: forall (es :: Effects) a. (forall (e :: Effects). StateSource e -> Eff (e :& es) a)
-> Eff es a	͘

runPureEff $ withStateSource $ \source -> do
  n <- newState source 5
  total <- newState source 0

  withJump $ \done -> forever $ do
    n' <- get n
    modify total (+ n')
    when (n' == 0) $ jumpTo done
    modify n (subtract 1)

  get total
15

Effectful operations

newState #

Arguments

:: forall (e :: Effects) s (es :: Effects). StateSource e
-> s	The initial value for the state handle
-> Eff es (State s e)	A new state handle

runPureEff $ withStateSource $ \source -> do
  n <- newState source 5
  total <- newState source 0

  withJump $ \done -> forever $ do
    n' <- get n
    modify total (+ n')
    when (n' == 0) $ jumpTo done
    modify n (subtract 1)

  get total
15