Copyright	(c) Edward Kmett & Sjoerd Visscher 2011
License	BSD3
Maintainer	ekmett@gmail.com
Stability	experimental
Safe Haskell	Safe-Inferred
Language	Haskell2010

Control.Monad.Representable.State

Description

A generalized State monad, parameterized by a Representable functor. The representation of that functor serves as the state.

Synopsis

type State g = StateT g Identity
runState :: Representable g => State g a -> Rep g -> (a, Rep g)
evalState :: Representable g => State g a -> Rep g -> a
execState :: Representable g => State g a -> Rep g -> Rep g
mapState :: Functor g => ((a, Rep g) -> (b, Rep g)) -> State g a -> State g b
newtype StateT g m a = StateT {
- getStateT :: g (m (a, Rep g))
}
stateT :: Representable g => (Rep g -> m (a, Rep g)) -> StateT g m a
runStateT :: Representable g => StateT g m a -> Rep g -> m (a, Rep g)
evalStateT :: (Representable g, Monad m) => StateT g m a -> Rep g -> m a
execStateT :: (Representable g, Monad m) => StateT g m a -> Rep g -> m (Rep g)
mapStateT :: Functor g => (m (a, Rep g) -> n (b, Rep g)) -> StateT g m a -> StateT g n b
liftCallCC :: Representable g => ((((a, Rep g) -> m (b, Rep g)) -> m (a, Rep g)) -> m (a, Rep g)) -> ((a -> StateT g m b) -> StateT g m a) -> StateT g m a
liftCallCC' :: Representable g => ((((a, Rep g) -> m (b, Rep g)) -> m (a, Rep g)) -> m (a, Rep g)) -> ((a -> StateT g m b) -> StateT g m a) -> StateT g m a
class Monad m => MonadState s (m :: Type -> Type) | m -> s where
- get :: m s
- put :: s -> m ()
- state :: (s -> (a, s)) -> m a

Documentation

type State g = StateT g Identity Source #

A memoized state monad parameterized by a representable functor g, where the representatation of g, Rep g is the state to carry.

The return function leaves the state unchanged, while >>= uses the final state of the first computation as the initial state of the second.

runState Source #

Arguments

:: Representable g

=> State g a

state-passing computation to execute

-> Rep g

initial state

-> (a, Rep g)

return value and final state

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

evalState Source #

Arguments

:: Representable g

=> State g a

state-passing computation to execute

-> Rep g

initial value

-> a

return value of the state computation

Evaluate a state computation with the given initial state and return the final value, discarding the final state.

```
evalState  m s = fst  (runState  m s)
```

execState Source #

Arguments

:: Representable g

=> State g a

state-passing computation to execute

-> Rep g

initial value

-> Rep g

final state

Evaluate a state computation with the given initial state and return the final state, discarding the final value.

```
execState  m s = snd  (runState  m s)
```

mapState :: Functor g => ((a, Rep g) -> (b, Rep g)) -> State g a -> State g b Source #

Map both the return value and final state of a computation using the given function.

runState  (mapState  f m) = f . runState  m

newtype StateT g m a Source #

A state transformer monad parameterized by:

g - A representable functor used to memoize results for a state Rep g
m - The inner monad.

The return function leaves the state unchanged, while >>= uses the final state of the first computation as the initial state of the second.

Constructors

StateT

Fields

getStateT :: g (m (a, Rep g))

Instances

Instances details

(Functor f, Representable g, MonadFree f (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

wrap :: f (StateT g m a) -> StateT g m a #

(Representable g, MonadReader e m) => MonadReader e (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

ask :: StateT g m e #

local :: (e -> e) -> StateT g m a -> StateT g m a #

reader :: (e -> a) -> StateT g m a #

(Representable g, Monad m, Rep g ~ s) => MonadState s (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

get :: StateT g m s #

put :: s -> StateT g m () #

state :: (s -> (a, s)) -> StateT g m a #

(Representable g, MonadWriter w m) => MonadWriter w (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

writer :: (a, w) -> StateT g m a #

tell :: w -> StateT g m () #

listen :: StateT g m a -> StateT g m (a, w) #

pass :: StateT g m (a, w -> w) -> StateT g m a #

Representable f => BindTrans (StateT f) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

liftB :: Bind b => b a -> StateT f b a #

Representable f => MonadTrans (StateT f) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

lift :: Monad m => m a -> StateT f m a #

(Representable g, Functor m, Monad m) => Applicative (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

pure :: a -> StateT g m a #

(<*>) :: StateT g m (a -> b) -> StateT g m a -> StateT g m b #

liftA2 :: (a -> b -> c) -> StateT g m a -> StateT g m b -> StateT g m c #

(*>) :: StateT g m a -> StateT g m b -> StateT g m b #

(<*) :: StateT g m a -> StateT g m b -> StateT g m a #

(Functor g, Functor m) => Functor (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

fmap :: (a -> b) -> StateT g m a -> StateT g m b #

(<$) :: a -> StateT g m b -> StateT g m a #

(Representable g, Monad m) => Monad (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

(>>=) :: StateT g m a -> (a -> StateT g m b) -> StateT g m b #

(>>) :: StateT g m a -> StateT g m b -> StateT g m b #

return :: a -> StateT g m a #

(Representable g, MonadCont m) => MonadCont (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

callCC :: ((a -> StateT g m b) -> StateT g m a) -> StateT g m a #

(Representable g, Bind m) => Apply (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

(<.>) :: StateT g m (a -> b) -> StateT g m a -> StateT g m b #

(.>) :: StateT g m a -> StateT g m b -> StateT g m b #

(<.) :: StateT g m a -> StateT g m b -> StateT g m a #

liftF2 :: (a -> b -> c) -> StateT g m a -> StateT g m b -> StateT g m c #

(Representable g, Bind m) => Bind (StateT g m) Source #

Instance details

Defined in Control.Monad.Representable.State

Methods

(>>-) :: StateT g m a -> (a -> StateT g m b) -> StateT g m b #

join :: StateT g m (StateT g m a) -> StateT g m a #

stateT :: Representable g => (Rep g -> m (a, Rep g)) -> StateT g m a Source #

runStateT :: Representable g => StateT g m a -> Rep g -> m (a, Rep g) Source #

evalStateT :: (Representable g, Monad m) => StateT g m a -> Rep g -> m a Source #

Evaluate a state computation with the given initial state and return the final value, discarding the final state.

evalStateT  m s = liftM  fst  (runStateT  m s)

execStateT :: (Representable g, Monad m) => StateT g m a -> Rep g -> m (Rep g) Source #

Evaluate a state computation with the given initial state and return the final state, discarding the final value.

execStateT  m s = liftM  snd  (runStateT  m s)

mapStateT :: Functor g => (m (a, Rep g) -> n (b, Rep g)) -> StateT g m a -> StateT g n b Source #

liftCallCC :: Representable g => ((((a, Rep g) -> m (b, Rep g)) -> m (a, Rep g)) -> m (a, Rep g)) -> ((a -> StateT g m b) -> StateT g m a) -> StateT g m a Source #

Uniform lifting of a callCC operation to the new monad. This version rolls back to the original state on entering the continuation.

liftCallCC' :: Representable g => ((((a, Rep g) -> m (b, Rep g)) -> m (a, Rep g)) -> m (a, Rep g)) -> ((a -> StateT g m b) -> StateT g m a) -> StateT g m a Source #

In-situ lifting of a callCC operation to the new monad. This version uses the current state on entering the continuation. It does not satisfy the laws of a monad transformer.

class Monad m => MonadState s (m :: Type -> Type) | m -> s where #

Minimal definition is either both of get and put or just state

Minimal complete definition

state | get, put

Methods

get :: m s #

Return the state from the internals of the monad.

put :: s -> m () #

Replace the state inside the monad.

state :: (s -> (a, s)) -> m a #

Embed a simple state action into the monad.