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Re: The ". $" notation

This page is part of the web mail archives of SRFI 110 from before July 7th, 2015. The new archives for SRFI 110 contain all messages, not just those from before July 7th, 2015.



Alan Manuel Gloria:
> There's a subtle problem with ". $" though...
> 
> First:
> 
> a $ b
> ===>
> (a b) ; as described in the rationale for SUBLIST.
> 
> Then:
> 
> a . $ b
> ===>
> (a . b)
> 
> ???

Bug, and I think fixed.  Current development version of
"unsweeten" and the ANTLR implementation seem to work.
The Scheme implementation now does this:

$ printf 'a . $ b\n\n' | ./unsweeten
(a b)


Supporting ". $" does have a slight annoyance; it creates a minor
ambiguity in the grammar (basically, like a "dangling else" clause in many langauges).
I've been able to avoid those so far.  It's not a crisis, because we can
easily make it go first, but it is an annoyance.

--- David A. Wheeler