*scratch*.el

(defparameter *inst* nil)
(defun ast->3ac-helper (ast)
  (if (atom ast)
      (cond
        ((numberp ast)
            ast)
        ((symbolp ast)
            ast)
        (t
          (error "oops, don't know what this is")))

      (case (car ast)
         ((+ - * /)
           (let ((name (gensym "T")))
             (push `(,name = ,(ast->3ac-helper (cadr ast)) 
                             ,(car ast)
                             ,(ast->3ac-helper (caddr ast)))
                    *inst*)
             name
             )))))

(defun ast->3ac (ast)
 (format t ";; New instruction stream for: ~A~%" ast)
 (setf *inst* nil)
 (ast->3ac-helper ast)
 (setf *inst* (nreverse *inst*)))

(defun emit-3ac (3ac)
 (format t "~{~A~%~}" 3ac))


;; run some of these


(emit-3ac (ast->3ac '(+ 1 2)))
(emit-3ac (ast->3ac '(+ 1 (+ 2 3))))
(emit-3ac (ast->3ac '(+ 1 (+ 2 (+ 3 4)))))
(emit-3ac (ast->3ac '(+ 1 (* 2 (- 3 (/ 4 5))))))

(emit-3ac (ast->3ac '(+ A B)))
(emit-3ac (ast->3ac '(+ A (+ B C))))
(emit-3ac (ast->3ac '(+ A (+ B (+ C D)))))
(emit-3ac (ast->3ac '(+ A (* B (- C (/ D E))))))

(emit-3ac (ast->3ac '(+ 1 B)))
(emit-3ac (ast->3ac '(+ 1 (+ 2 C))))
(emit-3ac (ast->3ac '(+ 1 (+ 2 (+ 3 D)))))
(emit-3ac (ast->3ac '(+ 1 (* 2 (- 3 (/ 4 E))))))

(emit-3ac (ast->3ac '(+ (- (* 1 2) (/ 3 4)) (+ (- 5 6) (- 7 8)))))

(emit-3ac (ast->3ac '(+ (+ (- 1 2) (- 3 4)) (+ (- 5 6) (- 7 8)))))