Stable Numerics Subroutine Library
Programming Reference Manual
Version 1.2 DD-00006-012

3.4.1 Empty Interval

An empty Kaucher interval X = ∅ for X ∈ KR is defined as an interval where at least one of the bounds is undefined:

      -        -
X= {[x,x]|x=∅ ∨ x= ∅}= ∅.

Here, ∅ ∉R, meaning the empty interval is not a real-valued interval. Consequently, no arithmetic operations can be performed on an empty interval.

In computational implementations, the empty interval is typically represented using qNaN (Quiet-Not-a-Number) values. Any arithmetic operation involving a qNaN will propagate the qNaN, ensuring that invalid or undefined operations do not yield misleading results.