úÎ^+                  semaphore-plus-0.1Control.Concurrent.UtilControl.Concurrent.LightSwitch Control.Concurrent.ReadWriteLockwithQSem LightSwitchnewLightSwitchlockLightSwitchunlockLightSwitchwithLightSwitch ReadWriteLocknewReadWriteLockreadLock readUnlock withReadLock writeLock writeUnlock withWriteLockcountermutex semaphore mutateIORef readSwitch roomEmpty turnstile