module Graph:S
Imperative Undirected Graphs implemented with adjacency matrices.
Vertices are integers in 0..n-1.
A vertex label is the vertex itself.
Edges are unlabeled.
include Sig.I
val make : int -> tCreation. graphs are not resizeable: size is given at creation time.
Thus make must be used instead of create.
Note: add_vertex and remove_vertex have no effect.
clear only removes edges, not vertices.