Graphs package: No error when handling negative adjacency matrices

[MikeAdamer]

When accidentally handing an adjacency matrix with negative entries it the "Graphs" package gives output which looks correct, but the edge set is empty.

E.g.:

A = matrix{{0,-1},{-1,0}}
G = digraph A

Should it throw an error when any entry in the adjacency matrix is negative?

[DanGrayson]

@b-stone @windisch @dcookii

[windisch]

I even would say that an exception should be thrown if any entry of the provided adjacent matrix is not in {0, 1}.

[DanGrayson]

Who would like to make the change?

[bstone]

I am traveling right now, but I can work on this next week if someone does not beat me to this.