Let $X$ be a D11: Set such that

(i)	$\mathcal{P}(X)$ is the D80: Power set of $X$
(ii)	$\{ 0, 1 \}^X$ is the D4213: Set of Boolean functions from $X$ to $\{ 0, 1 \}$

The indicator function operator on $\mathcal{P}(X)$ is the D18: Map \begin{equation} \mathcal{P}(X) \to \{ 0, 1 \}^X, \quad E \mapsto I_E \end{equation}