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I'm currently reading "Engineering a Compiler" book. In the chapter that explanes computing epsilon-closure there is listed the following algorithm:enter image description here

But I couldn't understand what does $E(n)$ and $E(p)$ mean. I know that it has something to do with sets.

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For each state $n \in N$, we maintain a set of states $E(n)$. Eventually, $E(n)$ would contain all states reachable from $n$ via $\epsilon$-transitions.

You can think of $E$ as an array of sets. The notation $E(n)$ just means the value of $E$ at position $n$. So $E(p)$ is just the value of $E$ at position $p$.

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  • $\begingroup$ It may be useful to note that this notation probably maps into concrete syntax that looks more like E[n] := {n} in many programming languages $\endgroup$ – Curtis F Aug 23 '19 at 21:04

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