### TAU-INTERVAL-HI

access the upper bound of a tau interval
Major Section: TAU-SYSTEM

It is the case that

(tau-interval-hi (make-tau-interval dom lo-rel lo hi-rel hi)) = hi

For a well-formed interval, `hi`

is either `nil`

, denoting positive
infinity, or a rational number giving the upper bound of the interval.
It must be the case that the upper bound is weakly above the lower bound
of a well-formed interval.

When the domain of an interval is `INTEGERP`

, there are additional
constraints on the other components. See make-tau-interval.