module Digraph:`S`

Imperative Directed 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 -> t`

Creation. 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.