// weightFuncFor returns a constructed weight function for g.
func weightFuncFor(g graph.Undirected) func(x, y graph.Node) float64 {
if wg, ok := g.(graph.Weighter); ok {
return func(x, y graph.Node) float64 {
w, ok := wg.Weight(x, y)
if !ok {
return 0
}
if w < 0 {
panic(negativeWeight)
}
return w
}
}
return func(x, y graph.Node) float64 {
e := g.Edge(x, y)
if e == nil {
return 0
}
w := e.Weight()
if w < 0 {
panic(negativeWeight)
}
return w
}
}
