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From: Alan Mackenzie <acm@muc.de>
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Subject: Is it possible for a macro to expand to nothing?
Date: Mon, 23 Nov 2009 14:56:47 +0000 (UTC)
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That is, not to a call to a null defun, but truly to nothing: i.e., the
ensuing code (as least, when byte compiled) will be identical to what it
would have been, had the macro invocation been omitted.

I want something like this:

(defmacro ifdef (condition &rest forms)
  "If the compile time CONDITION is non-nil, dump the FORMS to the
calling defun.  Otherwise do nothing."
  ......)

-- 
Alan Mackenzie (Nuremberg, Germany).