fpf{-}inv{-}rename($r$;${\it rinv}$;$f$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$<$mapfilter($\lambda$$x$.outl(${\it rinv}$($x$));$\lambda$$x$.isl(${\it rinv}$($x$));$f$.1), ($f$.2) o $r$$>$