sicp-ex-5.10

  
  
 ;; add an inc instruction. (inc <register-name>), add 1 to the value of register-name. 
  
 (define (make-execution-procedure inst labels machine 
                                           pc flag stack ops) 
  (cond ((eq? (car inst) 'assign) 
                 (make-assign inst machine labels ops pc)) 
        ((eq? (car inst) 'test) 
                 (make-test inst machine labels ops flag pc)) 
            ((eq? (car inst) 'branch) 
                 (make-branch inst machine labels flag pc)) 
            ((eq? (car inst) 'goto) 
                 (make-goto inst machine labels pc)) 
            ((eq? (car inst) 'save) 
                 (make-save inst machine stack pc)) 
            ((eq? (car inst) 'restore) 
                 (make-restore inst machine stack pc)) 
            ((eq? (car inst) 'inc) 
                 (make-inc inst machine pc)) 
            ((eq? (car inst) 'perform) 
                 (make-perform inst machine labels ops pc)) 
            (else (error "Unkown instruction type -- ASSEMBLE" 
                                 inst)))) 
  
 (define (make-inc inst machine pc) 
  (let ((target  
                 (get-register machine (inc-reg-name inst)))) 
   (lambda () 
    (set-contents! target (+ (get-contents target) 1)) 
    (advance-pc pc)))) 
 (define (inc-reg-name inst) 
  (cadr inst))