Re: [Axiom-developer] pointers

[Tim Daly]

Note that, under this definition

a:Dequeue(Integer):= dequeue [1,2,3,4,5]
b:Queue(Integer):= queue [1,2,3,4,5]

hash(a) == hash(b)

This is because the internal data representation of both objects is:

 ((1 2 3 4 5))

Nevertheless, this is a perfectly reasonable hash function.

Tim


Bill Page wrote:
> Tim,
>
> Besides the fact that from the standard we only have that
>
>   (equal x y) implies (= (sxhash x) (sxhash y)).
>
> Do you see any reason why SXHASH is not used by default in SetCategory?
>
> Note: OpenAxiom currently defines this default:
>
>   add
>       hash(s : %):  SingleInteger == SXHASH(s)$Lisp
>
> Regards,
> Bill Page.
>
> On Mon, Nov 9, 2009 at 7:51 PM, Tim Daly <address@hidden> wrote:
>   
> > ...
> > There is a lisp function to get the hash value of any object
> > call sxhash. You can call it.
> >
> > SXHASH(a)$Lisp
> >
> > Note that if
> >
> > c:=Integer
> >
> > then
> > EQ(a,c)$Lisp is false
> > SXHASH(a)$Lisp is not equal to SXHASH(c)$Lisp
> >
> > Thus the hash function you seek already exists.
> > You just have to accept the fact that Spad is only syntactic
> > sugar for lisp code and lisp is not evil.
> >     
>
>