runState -package:transformers

Unwrap a state monad computation as a function. (The inverse of state.)

Run a State effect with local state.

Unwrap a state monad computation as a function. (The inverse of state.)

Encapsulation of a state-using computation, exposing the initial and final states. Typical usage in arrow notation:

proc p -> do
...
(result, final_state) <- (|runState cmd|) init_state

Run the State effect with the given initial state and return the final value along with the final state.

Run a State effect starting from the passed value, applying a continuation to the final state and result.

runState k s (pure a) = k s a

runState k s get = k s s

runState k s (put t) = k t ()

Run a State effect starting from the passed value.

runState s (pure a) = pure (s, a)

runState s get = pure (s, s)

runState s (put t) = pure (t, ())

Run a lazy State effect, yielding the result value and the final state. More programs terminate with lazy state than strict state, but injudicious use of lazy state may lead to thunk buildup.

runState s (pure a) = pure (s, a)

runState s get = pure (s, s)

runState s (put t) = pure (t, ())

Run a State effect starting from the passed value.

runState s (pure a) = pure (s, a)

runState s get = pure (s, s)

runState s (put t) = pure (t, ())

Run a State effect

Run a State effect

Handler for State effects.

Run a State effect with local state.

>>> runPureEff $ runState 10 $ \st -> do
n <- get st
pure (2 * n)
(20,10)

Interpret the State effect.

This is the state record that controls the output style.

Runs a monadic generating action in the State monad using a pure pseudo-random number generator.

Examples

>>> import System.Random.Stateful

>>> let pureGen = mkStdGen 137

>>> runStateGen pureGen randomM :: (Int, StdGen)
(7879794327570578227,StdGen {unStdGen = SMGen 11285859549637045894 7641485672361121627})

Runs a monadic generating action in the ST monad using a pure pseudo-random number generator.