Control.Monad.Ref

Documentation

class Monad m => MonadRef r m | m -> r where

The MonadRef type class abstracts over the details of manipulating references, allowing one to write code that uses references and can operate in any monad that supports reference operations.

Minimal complete definition

newRef, readRef, writeRef

Methods

newRef :: a -> m (r a)

Create a new reference

readRef :: r a -> m a

Read the value of a reference

writeRef :: r a -> a -> m ()

Write a new value to a reference

modifyRef :: r a -> (a -> a) -> m ()

Mutate the contents of a reference

modifyRef' :: r a -> (a -> a) -> m ()

Strict version of modifyRef

Instances

MonadRef TVar STM

MonadRef IORef IO

MonadRef r m => MonadRef r (MaybeT m)

MonadRef r m => MonadRef r (ListT m)

MonadRef r m => MonadRef r (IdentityT m)

(Monoid w, MonadRef r m) => MonadRef r (WriterT w m)

(Monoid w, MonadRef r m) => MonadRef r (WriterT w m)

MonadRef r m => MonadRef r (StateT s m)

MonadRef r m => MonadRef r (StateT s m)

MonadRef r m => MonadRef r (ReaderT r' m)

(Error e, MonadRef r m) => MonadRef r (ErrorT e m)

MonadRef r m => MonadRef r (ContT r' m)

MonadRef (STRef s) (ST s)

class MonadRef r m => MonadAtomicRef r m | m -> r where

Minimal complete definition

atomicModifyRef

Methods

atomicModifyRef :: r a -> (a -> (a, b)) -> m b

Atomically mutate the contents of a reference

atomicModifyRef' :: r a -> (a -> (a, b)) -> m b

Strict version of atomicModifyRef. This forces both the value stored in the reference as well as the value returned.

Instances

MonadAtomicRef TVar STM

MonadAtomicRef IORef IO

MonadAtomicRef r m => MonadAtomicRef r (MaybeT m)

MonadAtomicRef r m => MonadAtomicRef r (ListT m)

MonadAtomicRef r m => MonadAtomicRef r (IdentityT m)

(Monoid w, MonadAtomicRef r m) => MonadAtomicRef r (WriterT w m)

(Monoid w, MonadAtomicRef r m) => MonadAtomicRef r (WriterT w m)

MonadAtomicRef r m => MonadAtomicRef r (StateT s m)

MonadAtomicRef r m => MonadAtomicRef r (StateT s m)

MonadAtomicRef r m => MonadAtomicRef r (ReaderT r' m)

(Error e, MonadAtomicRef r m) => MonadAtomicRef r (ErrorT e m)

MonadAtomicRef r m => MonadAtomicRef r (ContT r' m)