atoms{-}distinct(${\it tab}$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$\forall$$i$, $j$:\{0..$\parallel$${\it tab}$$\parallel$ $^{-}$\}. (st{-}atom(${\it tab}$;$i$) = st{-}atom(${\it tab}$;$j$)) $\Rightarrow$ ($i$ = $j$)