# Used for debugging only
	fun pretty_print do
		#print "core: {core.join(" ")} ({core.length})"
		#print "border: {border.join(" ")} ({border.length})"
		#print "crown: {crown.join(" ")} ({crown.length})"
		print "conflicts:"
		for e, c in conflicts do print "  {e or else "NULL"}: {c.join(" ")}"
	end