Avoid Destroying Arg Lists

(defmacro sum-plus-1 (&rest args)

(cons '+ (nconc args (list 1))))

(defun foo () (sum-plus-1 2 3))

(foo) returns 6

(foo) returns 7

(foo) returns 8

• Because the macro is destructively modifying the source code of the caller

• The source code stops changing when you compile it

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