There's nothing wrong with the definition of FooGraph. That's how you do it.
-- Lennart
On Tue, Feb 24, 2009 at 6:09 PM, Derek Gladding
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
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe