ma{-}interface{-}compose($g$;$X$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\lambda$$p$.let ${\it ds}$,$F$ = $p$ in $<$${\it ds}$, $\lambda$$p$.let $V$,$f$ = $p$ in $<$$V$, $\lambda$$s$.$g$ o $f$($s$)  $>$ o $F$$>$ o $X$