\begin{Verbatim}[commandchars=\\\{\},codes={\catcode`\$=3\catcode`\^=7\catcode`\_=8\relax}]
for each block B\PYGZus{}r in r do:
    for each block B\PYGZus{}s in s do:
        for each tuple t\PYGZus{}r in B\PYGZus{}r do:
            for each tuple t\PYGZus{}s in B\PYGZus{}s do:
                if t\PYGZus{}r and t\PYGZus{}s satisfy join condition:
                    add (t\PYGZus{}r, t\PYGZus{}s) to result
            end
        end
    end
end
\end{Verbatim}