-(define (time-+ time time-delta)
- (cons (+ (car time) (time-delta-sec time-delta))
- (+ (cdr time) (time-delta-usec time-delta))))
+(define (time-carry-correct time)
+ "Corrects/handles time microsecond carry.
+Will produce (0 . 0) instead of a negative number, if needed."
+ (cond ((>= (cdr time) 1000000)
+ (cons
+ (+ (car time) 1)
+ (- (cdr time) 1000000)))
+ ((< (cdr time) 0)
+ (if (= (car time) 0)
+ '(0 0)
+ (cons
+ (- (car time) 1)
+ (+ (cdr time) 1000000))))
+ (else time)))
+
+(define (time-delta+ time time-delta)
+ (time-carry-correct
+ (cons (+ (car time) (time-delta-sec time-delta))
+ (+ (cdr time) (time-delta-usec time-delta)))))
+
+(define (time-minus time1 time2)
+ (time-carry-correct
+ (cons (- (car time1) (car time2))
+ (- (cdr time2) (cdr time2)))))
+
+(define (time-plus time1 time2)
+ (time-carry-correct
+ (cons (+ (car time1) (car time2))
+ (+ (cdr time2) (cdr time2)))))