Re: [GD-General] Re: Simulating constrained genericity in C++

[Joe <dar...@ya...>]

So assuming point2d was an interface too, wouldn't you
just do
interface point3d extends point2d{
public float z();
}
and then your old implimentation should work

>
>Sure, here is the initiale code in Java (or something fairly close, I'll
>probably get the syntax wrong):
>
>interface point3d {
>  public float x();
>  public float y();
>  public float z();
>}
>
>class point3d_impl implements point3d { ... }
>
>Now somebody has written some code that only works on 2d points, like so:
>
>  public int dist(point2d p1, point2d p2)
>
>where point2d has the expected interface definition.  Can we pass objects
>of type point3_impl to this method?  If inheritence defines subtyping
>(with the implements keyword being a form of inheritence)  then one
>cannot.  If names and their types define the subtyping relationship then
>this is perfectly legal.
>
>This isn't the best motivating example, but it should be easy enough to
>understand the principle.
>
>Patrick
>
>
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