\begin{frame} \frametitle{Combinators} \vspace{-4ex} \begin{itemize} \item Let $B = S(KS)K$. We have \begin{align*} Bxyz = S(KS)Kxyz &\pause\to KSx(Kx)yz\\ &\pause\to S(Kx)yz \\ &\pause\to Kxz(yz) \\ &\pause\to x(yz) \end{align*} \pause \item Let $C = S(BBS)(KK)$. We have \begin{align*} Cxyz &\to^* xzy \end{align*} \pause \item Exercise: find a combinator $F$ such that $Fxy = yx$. \end{itemize} \end{frame}