backquote

[Jon L White <jonl@lucid.com>]

re: Could you forward this doubly nested example to me, so that the Genera
    reader >will< be able to parse it in future releases?

I think it is ``(,@,@x).  Believe it or not, one can "crank" the rules
of CLtL p349-50 to come up with a meaning for it.  Lucid, Xerox, and
VAXLISP get it "right" according to that meaning.  Several others generate
a read-time error (which is what I think Symbolics 7.0 does).  I've seen
some that parse it without error but subsquently generate wrong code.

As to whether this was ever used in naturally occurring code -- I dunno.
Ask QUUX (Guy L Steele).


-- JonL --


P.S.: When trying to work out an example using the rules of CLtL p340-50, 
      it's important to remember that the square-brackets are part of the 
      syntax of that crufty litle production-rule language. They are not
      meta-meta-syntax.