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

> I was attempting to create a useful toString() method for Tuples. So I started 
> by writing the following:
> 
> String toString(( <T>t,<U> u))
> {
>   return "("+t.toString()+","+u.toString()+")";
> }
> 
> But that did not work. Apparently generics within tuples don't work.

They do, it's just a problem a syntax. Type parameters are always introduced 
at the head of the method declaration:

<T,U> String toString(( T t, U u )) = "(" t "," u ")";

Note that you can use + for string concatenation if you are more comfortable 
with it. To use toString, you would need to guarantee that the tuple elements 
are not null (which is possible with <!T,!U> but it's less general).

> Please locate the bug that caused the problem. What is "unknown" anyway?

I think you are using an old version. I tried with 0.9.11, and I can't 
reproduce the exception. "unknown" does not exist anymore (it was used for 
unknown type parameters, especially with imported Java code, but not a single 
'?' is used, consistently with generic wildcards).


> Why 
> does "encountering a '<' not match a '<IDENT>'"?

JavaCC uses <IDENT> to mean "a token of kind IDENT", that is, "an identifier".

> Can we make it possible to 
> enable generics within tuples? 

Yes, it is possible ;-)

> And finally: Can we make some mechanism for using tuples as more general data 
> type and write code that can deal with tuples of arbitrary length,

I suppose we could add a type nice.lang.Tuple and make all tuple types 
subtypes of it. Then nice.lang could have a method:

?Object[] elements(Tuple t) //= cast(t);


With this, you could write methods that work an any tuple, like toString.

How does this sound?

Daniel


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