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I am currently writing a graph object in Swift, I see that there are different types of graphs, some that are undirected and some that are directed. Here are my questions :

  • Can a graph be both directed and undirected, is there a specific name for such graph?
  • What is the common approach to make an edge that would be bi-directionnal but whose weight depends on the direction you are following. Would it be acceptable to make an edge that hold two weights, one for each direction? Or should I create two edges?

Thank you.

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    $\begingroup$ I have never seen anyone try to have an undirected edge whose weight is different in each direction. If you want that, use two directed edges. $\endgroup$ – David Richerby Jun 17 '16 at 13:46
  • $\begingroup$ @DavidRicherby Thank you, I'll use directed edges than, especially since all the documentation online will use that too. $\endgroup$ – Trevör Jun 17 '16 at 13:48
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A graph that is both directed and undirected is called a Mixed graph.

All graph libraries that I know don't have direction dependent edge properties. Hence I would advise against introducing them if two directed edges do the job.

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