The set of Negative Reals is defined as the union of the set of negative rationals and negative
irrationals, i.e.
$$NegReals = I^- \cup Q^-$$
where \(I^-\) is the set of negative irrationals and \(Q^-\) is the set of negative rationals.
\(0\) may or may not be included (depending on the zero
argument).