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