Control.Concurrent.Class.MonadSTM.TVar

This module corresponds to TVar in "stm" package

MonadSTM

type family TVar m :: Type -> Type

A type of a TVar.

See TVar.

Instances

type TVar IO

Defined in Control.Monad.Class.MonadSTM.Internal

type TVar IO = TVar

type TVar (ReaderT r m)

Defined in Control.Monad.Class.MonadSTM.Internal

type TVar (ReaderT r m) = TVar m

newTVar :: MonadSTM m => a -> STM m (TVar m a)

newTVarIO :: MonadSTM m => a -> m (TVar m a)

readTVar :: MonadSTM m => TVar m a -> STM m a

readTVarIO :: MonadSTM m => TVar m a -> m a

writeTVar :: MonadSTM m => TVar m a -> a -> STM m ()

modifyTVar :: MonadSTM m => TVar m a -> (a -> a) -> STM m ()

modifyTVar' :: MonadSTM m => TVar m a -> (a -> a) -> STM m ()

stateTVar :: MonadSTM m => TVar m s -> (s -> (a, s)) -> STM m a

@since io-classes-0.2.0.0

swapTVar :: MonadSTM m => TVar m a -> a -> STM m a

check :: MonadSTM m => Bool -> STM m ()

See check.

MonadLabelSTM

labelTVar :: MonadLabelledSTM m => TVar m a -> String -> STM m ()

Name a TVar.

labelTVarIO :: MonadLabelledSTM m => TVar m a -> String -> m ()

MonadTraceSTM

traceTVar

Arguments

:: MonadTraceSTM m

=> proxy m

-> TVar m a

-> (Maybe a -> a -> InspectMonad m TraceValue)

callback which receives initial value or Nothing (if it is a newly created TVar), and the committed value.

-> STM m ()

Construct a trace output out of previous & new value of a TVar. The callback is called whenever an stm transaction which modifies the TVar is committed.

This is supported by IOSim (and IOSimPOR); IO has a trivial instance.

The simplest example is:

traceTVar (Proxy @m) tvar (\_ -> TraceString . show)

Note that the interpretation of TraceValue depends on the monad m itself (see TraceValue).

traceTVarIO :: MonadTraceSTM m => TVar m a -> (Maybe a -> a -> InspectMonad m TraceValue) -> m ()