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