[munich-lisp] multimethods, generic functions, multiple dispatch, ...

[Christian Schuhegger]

Andreas Hauser wrote:
> Christian.Schuhegger wrote @ Sat, 10 Sep 2005 08:58:48 +0200:
> 
> You seem to have forgotten to show the actual Lisp code.

sorry :)

(defmethod do-shapes-collide-p ((shape1 Triangle) (shape2 Circle))
   (...))
(defmethod do-shapes-collide-p ((shape1 Circle)   (shape2 Triangle))
   (do-shapes-collide-p shape2 shape1))
(defmethod do-shapes-collide-p ((shape1 Triange)  (shape2 Square))
   (...))
...


> 
> 
>>class Triangle implements Shape {
>>     public boolean collidesWith(Shape other) {
>>	other.collidesWithTriangle(this);
>>     }
>>     ...;
>>     public boolean collidesWithCircle(Circle s) {...;}
>>     public boolean collidesWithSquare(Square s) {...;}
>>     ...;
>>}
> 
> 
> While having methods with the same name but different signatures is
> certainly something i like, maybe in this case you just have problems
> with the objects you designed. I guess, we all know Java is limited,
> but let's not forget, they call it a feature.
> 
> 
> class Triangle implements Shape
> {
>      public 2Dspace space()
>      {
>          2DSpace my_space = xy[screen.x_dim][screen.y_dim];
>          // fill the matrix with pixels the Triangle occuppies
>          return my_space;
>      }
>      public boolean collidesWith(Shape other)
>      {
>          return overlap(other.space, this.space);
>      }
> }
> 
> So first, generalize the properties of your objects and then let them
> interact. I would also say that colliding and especially overlap()
> is something that the Object World should do.

and what do you do if you talk about vector objects and not pixel objects :)
-- 
Christian Schuhegger
http://www.el-chef.de/