queue-0.1.1.2: src/Data/Queue/Instances.hs

{-
 -      ``Data/Queue/Instances''
 -      (c) 2008 Cook, J. MR  SSD, Inc.
 -}
{-# LANGUAGE
        MultiParamTypeClasses,
        FlexibleInstances,
        CPP
  #-}

module Data.Queue.Instances
        ( Chan
        , MVar
        
#ifdef useSTM
        , module Data.Queue.Instances.STM
#endif
        
        ) where

import Data.Queue.Classes

#ifdef useSTM
import Data.Queue.Instances.STM
#endif

import Control.Concurrent

-- Chan : write only, because there's no atomic nonblocking read (that I know of)
instance NewFifo (Chan a) IO where
        newFifo = newChan
instance Enqueue (Chan a) IO a where
        enqueue = writeChan

-- MVar : one-item queue in IO monad
instance NewFifo (MVar a) IO where
        newFifo = newEmptyMVar
instance Enqueue (MVar a) IO a where
        enqueue = putMVar
instance Dequeue (MVar a) IO a where
        dequeue = tryTakeMVar