mk\_igrp($T$;${\it op}$;${\it id}$;${\it inv}$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$<$$T$, $\lambda$$x$,$y$. tt, $\lambda$$x$,$y$. tt, ${\it op}$, ${\it id}$, ${\it inv}$$>$