haskell
Shortest path algorithms assume that vertex only have one edge between them
In the case of vertices representing cities and edges representing roads. There are multiple edges between cities representing different route possibilities. Shortest path just gives me a list of nodes and there's no way to discover which edges are involved in the route from a list of nodes.
Yes, a lot of FGL was written assuming no multiple edges.
Unless you want to duplicate the function space, we can't change this until the next major version bump.
Understood, I think duplicating the function space is okay until the next major version. Another function could return a list of edges (lets call it an "EdgePath"). I naively think this would be a relatively simple fix. In the next version we can make Path = [LEdge] .