On Sun, Apr 11, 2010 at 4:15 PM, Ozgur Akgun
<ozgurakgun@gmail.com> wrote:
On 11 April 2010 22:54, Jason Dagit
<dagit@codersbase.com> wrote:
...
class Vehicle a where
data Car
data Truck
instance Vehicle Car where
instance Vehicle Truck where
Now you can have things that take a Car or a Truck or they can take a Vehicle instead.
moveVehicle :: Vehicle v => v -> Simulation ()
unfortunately, now you cannot use pattern matching while defining moveVehicle.
That's true. Although, if you're writing a simulation where Cars and Trucks are objects in that simulation, they are likely to be defined as records as they will probably have many fields. If that's the case, it's unlikely you'd be using pattern matching with them anyway. It's just a small step from there to using typeclass functions to access the parts you care about.
Jason