Re: Tuples, Generics, and compiler bugs, oh my!

On Monday 11 July 2005 2:03 am, Daniel Bonniot wrote:
> > Ok, I'm using the following:
> >
> > String toString( (int t, int u))
> > {
> >
> >   return "HELLO: (" + t.toString() + "," + u.toString() + ")";
> > }
> >
> > <T,U> String toString(( T t, U u )) = "(" t "," u ")";
> >
> > void main(String[] args)
> > {
> >   int a = 1;
> >   int b = 2;
> >   println((a,b).toString());
> > }
> >
> > and that prints:
> > [I@df6ccd
>
> Are you sure you recompiled before running? I just tried it, and I get the
> expected output:
> HELLO: (1,2)
>
> > Yes I was using 0.9.10 which I believed to be current, as it is still
> > linked to from the installation page for the rpm, even though 0.9.11 is
> > on sourceforge.
>
> Right, my mistake.
>
> > Just explain that:
> > (int i, String s, Cat c, int j)
> > Is actually shorthand for:
> > (int i, (String s, (Cat c, int j)))
>
> Hey, looks like Lisp! ;-)
>
> > Then it would be easy to write function for arbitrary length tuples:
> > <T> void Print((int i, String s, ?T ext = null)) = System.out.println(i s
> > Print(ext)); //Would get picked first because it is more specific.
>
> Yes, it's possible. The benefit over my solution is that it gives more
> static typing information. On the other hand I think it makes it impossible
> to write a method that accepts only couples with any second component. This
> could be solved by using, say, "..." as a type to mean "the rest of a
> tuple".
>
> I would think it might be sufficient in practice to match the first element
> of the tuple, and receive the rest as a second argument.
>
> In any case, this represents quite a lot more work than the nice.lang.Tuple
> solution (which could coexist in the long run). Would that one be good
> enough for you now? Or would somebody want to try to implement this
> proposal?

If that is easy to implement then yes, it would be useful. However ultimately 
I think we should do something like one of the mentioned ideas. (Perhaps a 
generic tuple could be "(<A>,<B>)" or abbreviated somehow.)


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