\begin{frame}{Exercise} \begin{exampleblock}{} Remove all unit production rules from \begin{talign} S \to Aa \mid B && A \to a \mid bc \mid B && B \to A \mid bb \end{talign} \pause Note that there are no $\lambda$-productions.\\ (So no need to first remove $\lambda$-productions.) \pause\medskip We determine all pairs $A \neq B$ with $A \Rightarrow^+ B$: \begin{talign} \mpause[1]{S \Rightarrow^+ B} && \mpause{A \Rightarrow^+ B} && \mpause{B \Rightarrow^+ A} && \mpause{S \Rightarrow^+ A} \end{talign} \pause\pause\pause\pause\pause Thus we add the following rules: \begin{talign} S &\to Aa \mid B \alert{\mpause[1]{\mid a}\mpause{\mid bc}\mpause{\mid A}\mpause{\mid bb}} \\ A &\to a \mid bc \mid B \alert{\mpause{\mid A}\mpause{\mid bb}} \\ B &\to A \mid bb \alert{\mpause{\mid a}\mpause{\mid bc}\mpause{\mid B}} \end{talign} \pause\pause\pause\pause\pause\pause\pause\pause\pause\pause Removing all unit production rules yields the final result: \begin{talign} S &\to a \mid bb \mid bc \mid Aa &&& A &\to a \mid bb \mid bc &&& B &\to a \mid bb \mid bc \end{talign} \end{exampleblock} \end{frame} \subsection{Chomsky Normal Form} \themex{Chomsky Normal Form}