Mike Sperber wrote:

 > You mean in a global hash table?  That's a hack around the lack of a
 > field in the syntax objects.

 But necessary if you want the generic car/cdr to be efficient, which is
 a more important constraint.  With this representation, you can use the
 primitive car/cdr unmodified on syntax objects.

 > To make it work efficiently, you'd have
 > to bring weakness in---a lot of machinery to duplicate functionality
 > that would trivially work if syntax objects were abstract and thus
 > extensible.

 I would differ on "trivially" ;-)  Reading through the psyntax implementation,
 I think complexity would be pretty much conserved no matter how you do it.

 Cheers
 Andre