Let $X \in \text{Random} [-\infty, \infty]$ be a D4381: Random basic number such that
| (i) | $X^+$ is the D1289: Basic function positive part of $X$ |
| (ii) | $X^-$ is the D1290: Basic function negative part of $X$ |
Then
\begin{equation}
|X| = X^+ + X^-
\end{equation}