Subversion Repositories programming

;Written By: Ira Snyder

;Due Date:   03-04-2005

;Homework #: HW13 (Exercise #15a)

;License: Public Domain

;;; Examples of the INC* macro input, and what it is transformed into

;

; Input:  (INC* x y z)

; Output: (progn

;           (setf z (1+ z))

;           (setf y (1+ y))

;           (setf x (1+ x))

;         )

;

; Input:  (INC* a)

; Output: (progn (setf a (1+ a)))

;

; Input:  (INC*)

; Output: (progn)

;;;

;;; The INC* macro takes an unlimited number of already initialized

;;; variables and increments them by 1. Note that variables that do not

;;; already have a value CAN NOT BE INCREMENTED.

(defmacro INC* (&rest VARS)

  (do ((VARS VARS (cdr VARS))

       (RET nil))

      ((null VARS) (cons 'progn RET))

    (setf RET (cons `(setf ,(car VARS) (1+ ,(car VARS))) RET))

  )

)