Re: DEFMACRO

[JONL@MIT-AI]

Expansion for &optional arguments fails to set up correct variable 
environment, as in standard DEFUNing, so that &optional may be initialized
to same value as some of the requireds.  Also, the destructuring for the
&optionals causes multiple-evaluations of the default-value computation
for that &optional.  Example of lossage
(DEFMACRO FOO ((A . B) &OPTIONAL 
                       ((C . D) (PROG2 (PRINT 'OPTIONALIZING) (CONS 1 B))))
   `(LIST ,A ,B ,C ,D))
expands into


(MACRO FOO
       (*MACROARG*)
       (AND (OR (< (LENGTH *MACROARG*) 2) (> (LENGTH *MACROARG*) 3))
	    (ERROR '|-- wrong number of args to a macro.|
		   (LIST '((A . B)
			   &OPTIONAL
			   ((C . D)
			    (PROG2 (PRINT 'OPTIONALIZING) (CONS 1 B))))
			 *MACROARG*)))
       ((LAMBDA (D C B A) (LIST 'LIST A B C D))
	(CDR (COND ((CDR (CDR *MACROARG*)) (CAR (CDR (CDR *MACROARG*))))
		   (T (PROG2 (PRINT 'OPTIONALIZING) (CONS 1 B)))))
	(CAR (COND ((CDR (CDR *MACROARG*)) (CAR (CDR (CDR *MACROARG*))))
		   (T (PROG2 (PRINT 'OPTIONALIZING) (CONS 1 B)))))
	(CDR (CAR (CDR *MACROARG*)))
	(CAR (CAR (CDR *MACROARG*)))))

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