What happens if you have,
data UserRoute = Find Int Int
you need a instance:
instance (GToURL f, GToURL g) => GToURL (f :*: g)
I think?
But the fromURL / gfromURL functions do not have a way to indicate how much of the input they consumed -- which I think will be a problem?
I believe the current code works because it assumes that each call to gfromURL will consume all the remaining input. But when your constructor has two arguments, the first one better not consume all the rest of the input..
- jeremy