- '((start . 0) (paused . 0) (state . stopped)))
-
-(define (start-timer timer)
- (assoc-set! timer 'start (SDL_GetTicks))
- (assoc-set! timer state 'running))
-
-(define (stop-timer timer)
- (assoc-set! timer 'state 'stopped))
-
-(define (get-time timer)
- (cond ((eq? (assoc 'state timer) 'stopped) 0)
- ((eq? (assoc 'state timer) 'paused) (assoc 'paused timer))
- (else (- (SDL_GetTicks) (assoc 'start timer)))))
-
-(define (pause-timer timer)
- (cond ((eq? (assoc 'state timer) 'running)
- (assoc-set! timer 'paused (- (SDL_GetTicks) (assoc 'start timer)))
- (assoc-set! timer 'state 'paused))))
-
-(define (resume-timer timer)
- (cond ((eq? (assoc 'state timer) 'paused)
- (assoc-set! timer 'start (- (SDL_GetTicks) (assoc 'paused timer)))
- (assoc-set! timer 'state 'running))))
+ (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))))))))