Dijkstra undirected

[dionyziz]

This patch changes the behavior of undirected graph functions inEdges and outEdges to return all the edges. This is in accordance to the relevant mathematical literature where, typically, when discussing "out edges" or "in edges" of undirected graphs, we mean all the edges.

Because the Dijkstra shortest path algorithm uses the outEdges function, it did not always work on undirected graphs. The behavior worked only when the natural order of the edges matched the shortest path traversal order of the edges; otherwise incorrect (such as Infinity) path lengths would be returned.

This patch adds a regression test for this edge case.

Merging this patch will require updating the documentation, which I will do as soon as it is merged.

Fix #42

[BudgieInWA]

As nodeEdges, inEdges and outEdges all exists for undirected graphs, what if outEdges guaranteed that for each returned edge e, e.v === v and inEdges gauranteed that e.w === v. This is a condition that is always true for directed graphs, and it is a condition that one might assume is always true by the name of the method. It is also a condition that is very useful, for example it would mean that the ternary on dijkstra.js#24 would not be needed (if the edgeFn argument didn't exist).

nodeEdges could guarantee that edges are returned in a consistent orientation, which would be convenient when edges need to be processed just once.

[assafsun]

Hi @dionyziz

I'm trying to review the open PR in order to reduce the amount of issues and PRs.
I reviewed your PR, nice work!
Two main item that I saw are:

1. merge action of lodash was not defined.
2. The nodeedges function extraction result in test failures.

I took your changes and kept a simpler flow based on your changes and the tests )With your new test) pass. the undirect graph will use the entire node edges and just the in or out.

You can see my changes in the PR that I will create

In case you are you still here and want to progress your work, feel free to comment and review the changes :)