gcd\_reduce($p$; $q$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$spreadn((TERMOF\{gcd{-}reduce:ObjectId, 1:l\}($p$,$q$)); $g$,$a$,$b$,${\it rest}$.$<$$g$, $a$, $b$$>$)