priority-sync-0.2.1.0: PrioritySync/Internal/Prioritized.hs

{-# LANGUAGE TypeFamilies #-}

module PrioritySync.Internal.Prioritized
    (Prioritized(..))
    where

import Control.Concurrent.STM

-- | Reprioritize a task.  This has no effect on a target that has already left the queue.
class Prioritized p where
    type Priority p :: *
    reprioritize :: p -> (Priority p -> Priority p) -> STM ()

instance (Prioritized p) => Prioritized (Maybe p) where
    type Priority (Maybe p) = Priority p
    reprioritize Nothing = const $ return ()
    reprioritize (Just p) = reprioritize p