Stable Numerics Subroutine Library
Programming Reference Manual
Version 1.1 DD-00006-011

3.1.4 Bounded and Whole Interval

An interval X ∈IR  is considered to be bounded if -
x,x∈R  and are finite. If either but not both of x or -
x are ± ∞ with the respective sign the interval is considered to be a lower bounded or upper unbounded interval.

If x= -∞ and -
x= ∞ the interval spans the whole x∈ R  space, this is called a whole interval.

A special case is    -
x= x= ∞ which is by definition an empty interval, as there will be no elements in the resulting interval set.