He Nathan,
I would create an data type (SpaceObject), which holds the Position and an
object. Then I create a typeclass for SpaceObject, which has the function
move in it. Functions which all objects have are moved in the typeclass:
type Position = (Double, Double)
data SpaceObject a = SO a Position
data RocketObject = RocketObject {
stuff :: String
}
data SpaceShipObject = SpaceShipObject {
bla :: Int
}
type Rocket = SpaceObject RocketObject
type SpaceShip = SpaceObject SpaceShipObject
class ScreenObject a where
move :: a -> Position -> a
instance ScreenObject (SpaceObject obj) where
move (SO obj (x,y) ) (dx, dy) = SO obj (x + dx, y + dy)
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On Tue, May 18, 2010 at 5:21 AM,
Hi,
I learning haskell and I am trying to understand how model certain things in it. As I have been doing a lot of C++ programming so far. Let's imagine we want to write a game. In the game there are spaceships and rocks (image something like astroids :) ). Now both spaceships and rocks have a position and can move. Spaceships can shoot, while rocks can explode. In C++, I would do (simplified):
class ScreenObject { float x,y; void move(dx,dy){x+=dx;y+=dy;} };
class Spaceship : public ScreenObject { void shoot(){...} };
class Rocket : public ScreenObject { void explode(){...} };
But what would I do in haskell? Ok, I can define a typeclass "ScreenObjectType" that has a move function (taking an object, retuning an moved object). But I do not want to implement "move" for both Spaceship and Rocket. Can I somehow give a default implementation for move that works on any datatype having an "x" and "y" element? Or what would I do? Can I somehow define a "base datatype" holding a x and y member form which Spaceship and Rocket derive? I feel like I am thinking to much OOP here. But the point is, I guess, that I want to avoid code duplication!
So I guess, it comes down to the questions: How would you model the scenario described above in haskell?
Thanks! Nathan _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners
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