The standard unsigned uniform real density function is the D218: Boolean function
\begin{equation}
\mathbb{R} \to \{ 0, 1 \}, \quad
x \mapsto I_{[0, 1]} (x)
\end{equation}
The standard unsigned uniform real density function is the D218: Boolean function
\begin{equation}
\mathbb{R} \to \{ 0, 1 \}, \quad
x \mapsto I_{x \in [0, 1]}
\end{equation}