RE: [Axiom-developer] Set Any and SXHASH

[Bill Page]

On April 5, 2007 1:04 PM Waldek Hebisch wrote:
> 
> Bill Page wrote:
> > 
> > If Set is implemented by sorting the linear order cannot be
> > domain specific since there certainly are domains from which
> > we might wish to form finite sets for which no "natural" order
> > can be defined, e.g. the domain Any. But I think it is always
> > possible to define some lexical ordering over the members of
> > all domains For example, the Axiom interpreter contains the
> > Lisp function LEXGREATERP in
> > 
> >   src/interp/ggreater.lisp.pamphlet
> > 
> > For the implementation of Set using sorting all that is required
> > is that the ordering be constant within an Axiom session.
> >
> 
> You need an order which is consistent with equality.

I agree.

> Since equality is domain-specific you need also domian-
> specific order.  I agree that we do not have one handy.

I do not agree. What do you think is wrong with LEXGREATERP
for this purpose?

> Producing order is not very hard.  Producing "from outside"
> order which agrees with equality seem to be expensive (I am
> affraid that you need to store all domain elements in a hash
> table). That is why I am saying about design bug.

Why?

> ...

Regards,
Bill Page.