Adds the vertex u to this graph.

If u already belongs to the graph, then nothing happens.

var g = new HashDigraph[Int]
g.add_vertex(0)
assert g.has_vertex(0)
assert not g.has_vertex(1)
g.add_vertex(1)
assert g.num_vertices == 2

Property definitions

graph $ MutableDigraph :: add_vertex
	# Adds the vertex `u` to this graph.
	#
	# If `u` already belongs to the graph, then nothing happens.
	#
	# ~~~
	# var g = new HashDigraph[Int]
	# g.add_vertex(0)
	# assert g.has_vertex(0)
	# assert not g.has_vertex(1)
	# g.add_vertex(1)
	# assert g.num_vertices == 2
	# ~~~
	fun add_vertex(u: V) is abstract
lib/graph/digraph.nit:720,2--732,33

graph $ HashDigraph :: add_vertex
	redef fun add_vertex(u)
	do
		if not has_vertex(u) then
			incoming_vertices_map[u] = new Array[V]
			outgoing_vertices_map[u] = new Array[V]
		end
	end
lib/graph/digraph.nit:953,2--959,4