newLISP the true champion of homoiconicity

Can your Lisp do this, /prog/?

(define (plus-minus a b)
  (begin
    (setf (nth '(1 2 0) plus-minus) (if (= (nth '(1 2 0) plus-minus) -) + -))
    (+ a b)))

(plus-minus 10 2)
8
(plus-minus 10 2)
12

newLISP treats code literally as data unlike Common Lisp or Scheme.

>>24
That still doesn't enlighten me as to how macros are supposed to be able to use regular functions (not defined in some sort of macrospace).