\documentclass[fleqn,leqno]{article}
\usepackage{hypertlabook}
\pdftitle{ASCII Text}
\addtolength{\textwidth}{20pt}
\fixverbatim
\begin{popup}
\begin{verbatim*}
RECURSIVE RandomRanking(_)
RandomRanking(S) == IF S = {} THEN << >>
                              ELSE LET e == RandomElement(S)
                                   IN  <<e>> \o RandomRanking(S \ {e})
\end{verbatim*}
\end{popup}
\makeasciipopup