# Returns true if and only if `vertices` is a path of this digraph.
	#
	# ~~~
	# var g = new HashDigraph[Int]
	# g.add_arc(1, 2)
	# g.add_arc(2, 3)
	# g.add_arc(3, 4)
	# assert g.has_path([1,2,3])
	# assert not g.has_path([1,3,3])
	# ~~~
	fun has_path(vertices: SequenceRead[V]): Bool
	do
		for i in [0..vertices.length - 1[ do
			if not has_arc(vertices[i], vertices[i + 1]) then return false
		end
		return true
	end