;; i have a bunch of functions that work in a similar way to the below one
;; basically F is either bound to a single number F = 8L + R, or it is the 
;; two numbers L and R. 

;; further each operation has a default F that i would like to use if none has  been provided


(defun ADD (M &rest F) 
  (multiple-value-bind (L R) (apply #'field F)
    (let* ((m-word (memory-contents M))
	   (V (sub-instruction-as-in-load m-word L R))
	   (V-sign (WORD-SIGN V))
	   (rA *RA*)
	   (rA-sign (WORD-SIGN rA))
	   (result 0))
      (if (equal POSITIVE V-sign)
	  (if (equal POSITIVE rA-sign)
	      (setf result (+ V rA))
	      (setf result (- V (negate rA))))	      
	  (if (equal POSITIVE rA-sign)
	      (setf result (- rA (negate V)))
	      (setf result (- (+ (negate V)
				 (negate rA))))))
      (when (< result 0)
	(setf result (- result))
	(setf (WORD-SIGN result) NEGATIVE))
      (when (= result 0)
	(setf (WORD-SIGN result) rA-sign))
    (setf *RA* result))))