graph: Determining the order of a graph is too expensive

[gonum]

graph: Determining the order of a graph is too expensive

[UserAB1236872]

I agree and found the same thing to be true. The only thing keeping me from doing it was that, by happenstance, every time I needed the Order I also needed the NodeList. (Externally at least, internally in the implementations I could just take len(g.nodeMap))

[soniakeys]

Well an Order method certainly makes sense for our existing concrete types. For an implementation of dynamic or infinite graphs, the method might have to have a different meaning, maybe invalid, unknown, or the number known/visited/explored so far.

[UserAB1236872]

This is one of those few cases where it's kind of unfortunate that no analogue to +/-inf exists for integers.

[kortschak]

Since we are not using Len(), we can have Order() return a float64, then we have the capacity to return +/-inf.