helper:tempo   scheme

;;
;; The helper:tempo inner function  
;;
;; - handle max/min cases 
;; - handle values memory 
;; - call metro object methods
;;
(define helper:tempo
    (lambda (increment min-limit max-limit)
    (let 
        ((oldval *tempo*)
        (newval 0)) 
        ;
        (if *debug*
            (log-info increment min-limit max-limit oldval)
            )
        ;
        (if (and (negative? increment) 
                    (>= min-limit oldval))
            ;; when decreasing, min-limit can't be higher than old value
            (helper:print-tempo oldval 'show)