SICP Solutions

Section - 2.2 - Hierarchical Data and the Closure Property

Exercise 2.32

To find power set of a set, $S$, we can proceed as:

Power set of $S$ is:

• if $S = \phi$, then $\mathcal P(S) = \{ \phi \}$.
• if $S \ne \phi$, then choose any element $x \in S$, then:
$\mathcal P(S) = \mathcal P(S \setminus \{ x \}) \; \cup \; \{ X \cup \{x\} \, \vert \; X \in \mathcal P(S \setminus \{ x \}) \}$.