"Undirected" mode for shortest paths with directed graphs

[etiennedeg]

This is a repost of this issue on the old repo.

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Hi,
This is a follow up of this discussion.
Is there a way to efficiently find shortest paths in a directed graph while ignoring the direction of the edges ? (so without casting to a directed graph)
R seems to have an "undirected" mode for this.

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Having thought more on this, better than a keyword in functions, it would be practical to have a new graph type that would be a wrapper around a directed graph, with redefinition of accessers to make it an undirected graph (a sort of graph view). This would avoid the heavy conversion to an undirected graph.

[jpfairbanks]

Yes I agree, solving this at the type level with a wrapper type that implements the abstract undirected graph API is the right move here. We don't want to add a kwarg for every function to add "undirected mode" just wrap it once and be done