# The recursive part of Tarjan's algorithm
	fun visit(u: V)
	do
		vertex_to_index[u] = index
		ancestor[u] = index
		index += 1
		stack.add(u)
		in_stack.add(u)
		for v in graph.successors(u) do
			if not vertex_to_index.keys.has(v) then
				visit(v)
				ancestor[u] = ancestor[u].min(ancestor[v])
			else if in_stack.has(v) then
				ancestor[u] = ancestor[u].min(vertex_to_index[v])
			end
		end
		if vertex_to_index[u] == ancestor[u] then
			var v
			loop
				v = stack.take
				in_stack.remove(v)
				sccs.union(u, v)
				if u == v then break
			end
		end
	end