use System.Threading


class X

	const numThreads = 8
	const numReps = 20
	const minSleepMS = 1
	const maxSleepMS = 20

	shared	

		var _rand = Random()
		
		var state = 0
		
		def delay
			Thread.sleep(_rand.next(.minSleepMS, .maxSleepMS))
		
		def work
			for n in .numReps, .readAndWriteState

		var locker = Object()
		
		def readAndWriteState
			# Change state from 0 to 1 and back to 0
			# with assertions along the way.
			# The delays allow other threads to modify the shared state
			# if a proper lock is not in place by whatever means.
			lock .locker
				.delay
				assert .state == 0
				.state = 1
				.delay
				assert .state == 1
				.state = 0
				.delay
				assert .state == 0

		def main
			threads = for i in .numThreads get Thread(ThreadStart(ref .work))
			for t in threads, t.start