\begin{frame} \small \begin{example} $t = \GREEN{(2:x)+((1:x):y)}$ \qquad \GREEN{\begin{tikzpicture}[on grid,baseline=(1).baseline] \matrix[ampersand replacement=\&,row sep=5mm,column sep=2mm]{ \& \& \& \node (1) {$+$}; \& \& \& \\ \& \node (2) {$:$}; \& \& \& \& \node (3) {$:$}; \& \\ \node (4) {$2$}; \& \& \node (5) {$x$}; \& \& \node (6) {$:$}; \& \& \node (7) {$y$}; \\ \& \& \& \node (8) {$1$}; \& \& \node (9) {$x$}; \& \\}; \draw (1) -- (2) (1) -- (3); \draw (2) -- (4) (2) -- (5); \draw (3) -- (6) (3) -- (7); \draw (6) -- (8) (6) -- (9); \draw (1) node[right] {$\,{}^\epsilon$}; \draw (2) node[left] {${}^1\,$}; \draw (3) node[right] {\alert<7>{$\,{}^2$}}; \draw (4) node[left] {${}^{11}\,$}; \draw (5) node[right] {$\,{}^{12}$}; \draw (6) node[left] {\alert<3>{${}^{21}\,$}}; \draw (7) node[right] {$\,{}^{22}$}; \draw (8) node[left] {${}^{211}\,$}; \draw (9) node[right] {\alert<5>{$\,{}^{212}$}}; \end{tikzpicture}} \begin{itemize} \item<2-> $t|_{21} = \alt<3->{\GREEN{1:x}}{?}$ \item<4-> $t(212) = \alt<5->{\GREEN{x}}{?}$ \item<6-> $t[\GREEN{x+3}]_{2} = \alt<7->{\GREEN{(2:x)+(x+3)}}{?}$ \smallskip \end{itemize} \end{example} \end{frame}