\begin{tabbing}
s{-}insert($x$; $l$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=rec{-}case($l$) of [] =$>$ cons($x$; []) $\mid$ $a$::${\it as}$ =$>$ $v$.if\= ($x$ =$_{0}$ $a$)\+\+
\\[0ex]then cons($a$; ${\it as}$)
\-\\[0ex]if $x$ $<$z $a$ then cons($x$; cons($a$; ${\it as}$)) else cons($a$; $v$) fi 
\-
\end{tabbing}