# Build a sequence of actions from the initial state to `self`
	# See `path` for a more detailed plan.
	fun plan: Sequence[A]
	do
		var res = new List[A]
		var node: nullable BacktrackNode[A] = self
		while node != null do
			var a = node.action
			if a != null then res.unshift(a)
			node = node.parent
		end
		return res
	end