[plt-scheme] match and xml structures

Matthew Flatt wrote:
>   For list-related administrative tasks:
>   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> 
> At Tue, 15 Jul 2003 14:42:34 -0400, David Van Horn wrote:
> 
>>However, structure subtypes still don't seem to match.
> 
> 
> Right. Unfortunately, we're stuck at this point.
> 
> The problem is that unit signatures don't include information about
> subtypes, so `match' has no way to know about subtypes. 

Ah, I see now.  Units don't export syntax objects, which is how the 
structure information is conveyed.  Eg. `comment' is not bound in xml.ss.

Just a couple more comments...

I happen to come across what seems like another bug in match.

    (match '((a 1) (b 1))
      (((or ('a _) ('b _)) ..1)
       #t))

    ;=> #t   Ok.

    (match '((a 1) (b 1))
      (((or ('a x) ('b x)) ..1)
       #t))

    ;cdr: expects argument of type <pair>; given #f

And I was wondering if the grammar for match could be slightly extended.

I believe that (and pat1 ... patn) could be (and lvp1 ... lvpn), 
likewise for `or' and `not'.

This would allow patterns such as

   (or ('p x) ...
       ('q x) ...)

(BTW, the online and distributed documentation for version 204 is 
missing the pattern syntax image. 
http://download.plt-scheme.org/doc/204/html/mzlib/mzlib-Z-H-21.html#node_sec_21.1)

-d