\begin{tabbing}
pairs{-}fpf(${\it eq}_{1}$;${\it eq}_{2}$;$L$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=$\langle$remove{-}repeats(${\it eq}_{1}$;map($\lambda$$p$.1of($p$);$L$))\+
\\[0ex]$,\,$$\lambda$$x$.reduce($\lambda$$p$,$l$. if eqof(${\it eq}_{1}$)(1of($p$),$x$)$\rightarrow$ insert(${\it eq}_{2}$; 2of($p$); $l$) else $l$ fi;nil;$L$)$\rangle$
\-
\end{tabbing}