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Re: Opaque syntax objects

This page is part of the web mail archives of SRFI 72 from before July 7th, 2015. The new archives for SRFI 72 contain all messages, not just those from before July 7th, 2015.

 > 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?  
 > 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.