\begin{frame}[fragile]{Simple Core Language (Syntax)}
  \begin{goal}{}
    Arithmetic expressions:
    \begin{talign}
      \aexp \;\;\; {::=} \;\;\;
        \boldsymbol{n} \;\mid\; \boldsymbol{x} \;\mid\; (-\aexp) \;\mid\; (\aexp + \aexp) \;\mid\; (\aexp - \aexp) \;\mid\; (\aexp * \aexp) 
    \end{talign}
  \end{goal}
  \pause
  where
  \begin{itemize}\vspace*{0.2ex}\setlength{\itemsep}{0.2ex}
    \item
      $\boldsymbol{n}$ is any integer numeral in $\setexp{ \ldots, -2, -1, 0, 1, 2, \ldots }$\pause{}
    \item
      $\boldsymbol{x}$ any variable\pause{}
    \item
      $*$ indicates multiplication\pause{}    
  \end{itemize}
   
  \begin{exampleblock}{}
    \begin{itemize}\vspace*{0.2ex}\setlength{\itemsep}{0.2ex}
      \item
        $42$\pause{}
      \item
        $y$\pause{}
      \item
        $4 + (x - 3)$\pause{}
      \item 
        $x + (x * (y - (5 + z)))$  
    \end{itemize}
  \end{exampleblock}
  \vspace{10cm}
\end{frame}