\begin{tabbing}
rps($x$; $y$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$bor(\=band(($x$ =$_{0}$ 2); ($y$ =$_{0}$ 0)); bor(band(($x$ =$_{0}$ 1); ($y$ =$_{0}$ 2)); band(($x$ =$_{0}$ 0); ($y$ =$_{0}$ 1)))\+
\\[0ex])
\-
\end{tabbing}