lnk{-}decl($l$;${\it dt}$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\langle$map($\lambda$${\it tg}$.rcv($l$,${\it tg}$);1of(${\it dt}$))$,\,$$\lambda$$k$.fpf{-}ap(${\it dt}$; IdDeq; 2of(outl($k$)))$\rangle$