\begin{tabbing}
ecl{-}ex($x$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$ecl\_ind($x$;$k$,${\it test}$.nil;$a$,$b$,$A$,$B$.merge($A$;$B$);$a$,$b$,$A$,$B$.merge($A$;$B$);$a$,$b$,$A$,$B$.merge($A$;$B$);$a$,$A$.$A$;$a$,$m$,$A$.$A$;$a$,$m$,$A$.\=if \=$m$=$_{2}$0$\rightarrow$\+\+
\\[0ex]$A$
\-\\[0ex]else s{-}insert($m$;$A$) fi;$a$,$l$,$A$.$A$)
\-
\end{tabbing}