-(defstruct timer (start 0) (paused 0) (state 'stopped))
-
-(defun start-timer (timer)
- (setf (timer-start timer) (SDL_GetTicks))
- (setf (timer-state timer) 'running))
-
-(defun stop-timer (timer)
- (setf (timer-state timer) 'stopped))
-
-(defun get-time (timer)
- (cond ((eq (timer-state timer) 'stopped) 0)
- ((eq (timer-state timer) 'paused) (timer-paused timer))
- (t (- (SDL_GetTicks) (timer-start timer)))))
-
-(defun pause-timer (timer)
- (cond ((eq (timer-state timer) 'running)
- (setf (timer-paused timer) (- (SDL_GetTicks) (timer-start timer)))
- (setf (timer-state timer) 'paused))))
-
-(defun resume-timer (timer)
- (cond ((eq (timer-state timer) 'paused)
- (setf (timer-start timer) (- (SDL_GetTicks) (timer-paused timer)))
- (setf (timer-state timer) 'running))))
-
+(define (make-timer)
+ (let ((start 0) (paused 0) (state 'stopped))
+ (lambda (op)
+ (case op
+ (('start-timer)
+ (set! start (SDL_GetTicks))
+ (set! state 'running))
+ (('stop-timer)
+ (set! state 'stopped))
+ (('get-time)
+ (cond ((eq? state 'stopped) 0)
+ ((eq? state 'paused) paused)
+ (else (- (SDL_GetTicks) start))))
+ (('pause-timer)
+ (cond ((eq? state 'running)
+ (set! paused (- (SDL_GetTicks) start))
+ (set! state 'paused))))
+ (('resume-timer)
+ (cond ((eq? state 'paused)
+ (set! start (- (SDL_GetTicks) paused))
+ (set! state 'running))))))))