Add function for finding all possible paths from a given node

[patrickdoc]

Add function for finding all possible paths from a given node

[patrickdoc]

Ok, I have added an example demonstrating how this might work. Forgive my handling of the Money values, I've not used it before, so it may be less than optimal.

hash-graph/examples/Currency.hs

Lines 15 to 17 in f18b143

	main = do
	let graph = mkGraph es ns
	print $ pathTree "EUR" graph

I've implemented a rough version of pathTree. My only warning is that it will infinitely loop on graphs containing self loops (e.g. an edge from "USD" to "USD"). This will return a list of edges, which should not lose any information from the graph.

[runeksvendsen]

Wonderful! Thanks a lot for implementing this, and doing it so fast.

Would you happen to know the time complexity of your
pathTree implementation?

[patrickdoc]

Hm, so I mostly used the algorithm from Graphalyze, which recursively calls match. I believe worst-case you are looking at something like N²E.

[runeksvendsen]

Great. I won't be using it for huge graphs, so I hope that won't become a problem.

I finally got the time to try out pathTree properly. I've extended the "Currency"/exchange rate example to a total of eight edges with four possible paths of length five (along with some pretty printing). See PR #5.