\frametitle {Prolog vs. Schelog}\begin {block}{Prolog}
    \begin{minted}[gobble=6]{prolog}
      do_insert(X,Y,[X|Y]).
      do_insert(X,[Y1|Y2],[Y1|Z]) :- do_insert(X,Y2,Z).
    \end{minted}
  \end{block}
  \begin{block}{Schelog}
    \begin{minted}[gobble=6]{scheme}
      (define do-insert
        (%rel (x y y1 y2 z)
              ((x y (cons x y)))
              ((x (cons y1 y2) (cons y1 z))
               (do-insert x y2 z))))
    \end{minted}
  \end{block}