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Strange change in backquote expansion

From: Sascha Wilde
Subject: Strange change in backquote expansion
Date: Sat, 18 Aug 2007 23:34:19 +0200
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.1.50 (gnu/linux)

Hi *,

I'm not quite sure what to think about it, but something changed in
expansion of macro expansion, more precisely in expansion of

Old Emacs (including 22.0):
(defmacro debug-macro-test (arg)
  ``(,,@(list (list arg))))

(macroexpand '(debug-macro-test foo))
=> (list (foo))

Current HEAD:
(macroexpand '(debug-macro-test foo))
=> (list ((foo)))

note the extra parenthesis.

Please don't ask, what the code is supposed to do, this is a extremely
boiled down version of the problem.  I stumbled across this problem
when I noticed that DVC stopped working in HEAD recently.  (They are
using a somewhat esoteric macro, which suffers from this change in

Sascha Wilde
Well, *my* brain likes to think it's vastly more powerful than any
finite Turing machine but it hasn't proven that to me...
  -- Christopher Koppler in comp.lang.lisp

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