Connectedness of directed graphs

[simonschoelly]

Currently is_connected(g) is equivalent to is_weakly_connected(g) if g is a digraph. The English Wikipedia on the other hand says, that for a digraph, g is connected if for every pair of vertices (u, v) there is either a path from uto v or one from v to u.
To make stuff more complicated, I can't find that definition anywhere else in the literature. But apparanently this concept is called semi-connected in a lot of places (for example also in Networkx).
I would therefore propose to add a deprecation warning to is_connected for digraphs and also to implement a function is_semi_connected for digraphs.

Related issue: #368

[sbromberger]

There was a lot of discussion around this after #368. Paging @jpfairbanks.

[stale]

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[simonschoelly]

Can we revive this?

[sbromberger]

Sure. But I think this does what you want: is_weakly_connected is exactly

g is connected if for every pair of vertices (u, v) there is either a path from u to v or one from v to u.

So having is_connected(g::::DiGraph) equal is_weakly_connected(g) adheres to the Wikipedia definition. What am I misunderstanding?

[simonschoelly]

In the digraph

u <-- v --> w

there is no path from u to w or from w to u, but the graph is still weakly connected.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.