The signum function is the D4948: Integer function
\begin{equation}
\mathbb{R} \to \{ -1, 0, 1 \}, \quad
I_{(0, \infty)} (x) - I_{(-\infty, 0)} (x)
\end{equation}
The signum function is the D4948: Integer function
\begin{equation}
\mathbb{R} \to \{ -1, 0, 1 \}, \quad
I_{x \in (0, \infty)} - I_{x \in (-\infty, 0)}
\end{equation}
The signum function is the D4948: Integer function
\begin{equation}
\mathbb{R} \to \{ -1, 0, 1 \}, \quad
x \mapsto
\begin{cases}
1, \quad & x \in (0, \infty) \\
-1, \quad & x \in (-\infty, 0) \\
0, \quad & x = 0
\end{cases}
\end{equation}
