Heinrich Apfelmus
Ivan Lazar Miljenovic wrote:
Heinrich Apfelmus writes:
I was under the impression that I would have to define a new graph data type with FilePath as vertex type and make that an instance of Graph ? [..]
Well, we'll provide a Map-based one that lets you specify the vertex type as a type parameter; this functionality (type parameter being ued for the vertex type) won't be required since not all graphs will be able to chop and choose which vertex type to use.
Ah, that would indeed make it easy. Maybe make the map based graph generic, so that it can be used with any primitive graph implementation?
data VertexGraph node gr a b = VG (gr a b) (BiMap node (Vertex gr))
instance (Ord node, Graph gr) => Graph VertexGraph node gr where
Not sure I understand what the point of the `gr' is there; what I meant was something like: newtype MapGraph node a b = MG (Map node (Map node b, a, Map node b))
Well, you can consider the current Int vertex type to be a (not-so-) abstract vertex type; it might be an idea to wrap this up so people don't mess with it themselves though.
That would be much appreciated. :)
We'll consider this then. (*sigh* it's not enough that we're modernising this library, but we also have to hold the users hand for them in case they accidentally use the wrong Int? Gimme a break! :p) Actually, this might solve a problem that Thomas and I were discussing earlier where a Context can refer to vertices not in the graph (it won't completely remove the problem as you can still get the value from a different state of the graph, but will help remove obvious user error when manually constructing Context values). -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com