(define
	(:predicates
		(clear ?x)
		(on-table ?x)
		(arm-empty)
		(holding ?x)
		(on ?x ?y)
	)
	(:action pickup
		:parameters (?ob)
		:precondition 
			(and
				(clear ?ob)
				(on-table ?ob)
				(arm-empty)
			)
		:effect 
			(and
				(holding ?ob)
				(not (clear ?ob))
				(not (on-table ?ob))
				(not (arm-empty))
			)
	)
	(:action putdown
		:parameters (?ob)
		:precondition 
			(holding ?ob)
		:effect 
			(and
				(clear ?ob)
				(arm-empty)
				(on-table ?ob)
				(not (holding ?ob))
			)
	)
	(:action stack
		:parameters (?ob ?underob)
		:precondition 
			(and
				(clear ?underob)
				(holding ?ob)
			)
		:effect 
			(and
				(arm-empty)
				(clear ?ob)
				(on ?ob ?underob)
				(not (clear ?underob))
				(not (holding ?ob))
			)
	)
	(:action unstack
		:parameters (?ob ?underob)
		:precondition 
			(and
				(on ?ob ?underob)
				(clear ?ob)
				(arm-empty)
			)
		:effect 
			(and
				(holding ?ob)
				(clear ?underob)
				(not (on ?ob ?underob))
				(not (clear ?ob))
				(not (arm-empty))
			)
	)
)