\begin{frame}{LL Parsing} \begin{goal}{LL parsing} Parsing \emph{top-down} with a \emph{leftmost} strategy. \medskip Backtracking is \alert{not} allowed. \end{goal} LL parsing does not work for every context-free grammar. \pause\medskip \begin{goal}{} Starting point is a context-free grammar $G = (V,T,S,P)$: \begin{itemize} \item \alert{without useless variables} \item $\lambda$-productions and unit productions are allowed\\ (elimination often increases the size of the grammar) \end{itemize} \end{goal} \pause Steps of LL parsing: \begin{itemize} \item Construct sets $\first{A}$ and $\follow{A}$ for every variable $A$. \item Construct a parsing table. \item Parse the input word using the parsing table. \end{itemize} \end{frame}