fpf{-}rename(${\it eq}$;$r$;$f$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\langle$map($r$;1of($f$))$,\,$$\lambda$$x$.2of($f$)(hd(filter($\lambda$$y$.eqof(${\it eq}$)($r$($y$),$x$);1of($f$))))$\rangle$