[bitc-dev] Type compatibility at application

[Jonathan S. Shapiro]

On Fri, 2006-05-19 at 20:14 +0100, David Hopwood wrote:
> Jonathan S. Shapiro wrote:
> >>OK. Are you thinking of a case like:
> >>
> >>(define (f x:(vector 'a) #t)
> >>
> >>(define vec1:(vector int32)  (vector 1 2 3))
> >>(define vec2:(vector (mutable int32)) (vector 1 2 3 ))
> >>
> >>(define vecApp
> >>    (begin
> >>	(f vec1)
> >>	(f vec2)
> >>)
> > 
> > Yes. I am thinking of exactly this. And here is the weird part: if F can
> > operate correctly on (vector (non-mutable T)), then it will operate
> > equally correctly on (vector (mutable T)).
> 
> Isn't the compiled code for F on (vector (non-mutable T)) allowed the
> optimization of caching vector lookups, while the compiled code for F on
> (vector (mutable T)) would have to perform every lookup that appears in
> the source?

Yes, but I do not expect to ever see such an implementation. The
overhead of this class of over-specialization is considerable, and the
necessary supporting runtime complexity is overwhelming.

shap