automatic casting

automatic casting

[kartick Vaddadi]

in code such as this:

if (o instanceof Dog)
    {
    Dog d = (Dog)o;
    d.bark();
    . . .
    }

why not eliminate the requirement to cast, since the
instanceof ensures that the object is of the right
type;i.e., u should be able to write:

if(o instanceof Dog)
    {
    o.bark();
    . . .
    }

what do u think?
-kartick


	
		
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Re: automatic casting

[Paolo Bonzini]

> why not eliminate the requirement to cast, since the
> instanceof ensures that the object is of the right

You should ask Sun about this, not the GCC community; there are no GNU 
extensions to the Java language.  Anyway the answer is probably going to 
be that while this case is obvious, there are going to be more and more 
complicated cases that the compiler won't possibly figure out.

Paolo

Re: automatic casting

[Diego Novillo]

On Tue, 2004-08-31 at 08:49, kartick Vaddadi wrote:

> if(o instanceof Dog)
>     {
>     o.bark();
>     . . .
>     }
> 
I think this is the same issue reported in

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15525

If so, there may be a patch coming down the road to support this.


Diego.

Re: automatic casting

[Tom Tromey]

>>>>> "Diego" == Diego Novillo <dnovillo@redhat.com> writes:

Diego> On Tue, 2004-08-31 at 08:49, kartick Vaddadi wrote:
>> if(o instanceof Dog)
>> {
>> o.bark();
>> . . .
>> }

Diego> I think this is the same issue reported in
Diego> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15525
Diego> If so, there may be a patch coming down the road to support this.

This is related.  The original poster wanted a language extension.  I
don't think we'll do this; a language extension would need a strong
justification, and this particular extension would mean mixing flow
control with semantic analysis, which would be pretty ugly to
implement.

The PR is about removing redundant casts from the generated code.
I'll upload my patch into the PR soon.  It works ok, but as I recall
it needs VRP to remove everything.  When I upload it I'll put the info
in the PR.

Tom