Re: Object or <T> parameters

Quoting Bryn Keller <[email protected]>:

>I think it's reasonable. It might be nice to have it print name, type
>information, and so on. Even if it doesn't, I don't see what the issue
>is. If it's first class, you ought to be able to inspect it, IMHO.

I agree, it might be a useful feature. But, is the current behavior useful? I
personally don't think it is. It seems likely that whenever we write:
    x + f + y
when f is a function, we really mean:
    x + f() + y.
given that toString(t) doesn't do what you describe above.

> [email protected] wrote:
> >For example, why should the following program typcheck? What does
> >newInstance(getClass(() => true)) mean?:
> >    void main(String [] args) {
> >        let a = new Date();
> >        let b = newInstance(getClass(a));
> >        let c = () => true;
> >        let d = newInstance(getClass(a)); // ???
> >    }
> >  
> >
> Did you mean "let d = newInstance(getClass(c))"? I would think it would 
> create a new method. This would fail at runtime I imagine, since methods 
> probably wouldn't have no-arg constructors.

Yes, that is what I meant. What does getClass() mean for methods? 

> >That is, it seems that getClass should have type:
> >     <Object T> Class<T> getClass(T);
> >Where <Object T> means "not a function," possibly also "not a primitive
> type."
> >
> Helpful in that case, but not in this:
> 
> <T,U> List<U> callEach(List<T->U> funcs, T arg) {
>    List<U> result = new ArrayList();
>   for(T->U func : funcs) {
>     println("Calling " + func);
>     result.add(func(arg));
>   }
> }

I agree. And, even if you implement my suggestion then this would work just
fine, unchanged. I am merely saying it should be possible to say things like:
    <Object T> Class<T> getClass(T);
Which means that T must be an instance of an object type (interface, class, enum).

> >It is basically the same motivation that you had for delayed<T> in the
> >expression-local variables thread, namely catching likely typos during
> typechecking.
> >  
> >
> A worthwhile goal, but I'm not convinced that benefits outweigh the costs.

Fair enough. This is not a huge deal to me. I think it is something to consider
when implementing features based on the block call syntax(es).

- Brian




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