Please forgive me if I'm still mentally contaminated by the OO way of seeing (and discussing) the universe, but I'm trying to figure out how to "inherit an interface" from a multi-parameter type class.

I have a Graph class that's parameterisable by Node and Edge type:

class (Node a, Edge b) => Graph a b where
    (lots of stuff that you can do with Graph a b)

Now, I'd like to build a FooGraph on top of this that adds additional capabilities:

class (Graph a b) => FooGraph a b where
    (lots of additional stuff)

but this isn't allowed (kind mismatch).

Of couse, I can do:

class (Node a, Edge b) => FooGraph a b

but this means that I have to manually replicate the Graph a b operations in the FooGraph a b class definition, which is (a) work that the machine should (?) be able to do for me, and (b) fragile.

Any pointers / wisdom would be very much appreciated.

- Derek

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