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Re: Opaque syntax objects



 > From: Michael Sperber <sperber@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
 
 > I guess I didn't catch the drift of your earlier message:  Are you
 > implying that syntax objects can be opaque, and that CAR and CDR
 > should be extended to work on them?  
 
 If you would consider it okay for a subtype of the pair type to be
 called opaque, then I think yes.  
 
 > Does this mean, by transitivity,
 > any R5RS procedure that works on lists or pairs should also work on
 > syntax objects?  
 
 Indeed.
 
 > That's a tall order, and one not every implementor
 > might feel comfortable about.
 
 Understood.  At least an easily portable implementation is provided, which
 should mitigate their pain a little ;-)
 I have no illusions that the two big current syntax-case implementors will
 adopt it, but it does provide an almost completely backward compatible 
 superset of "portable syntax-case".  Users who are uncomfortable with 
 car/cdr can happily ignore them.   
 
 Cheers
 Andre