\documentclass[fleqn,leqno]{article}
\usepackage{hypertlabook}
\pdftitle{ASCII Text}
\fixverbatim
\begin{popup}
\begin{verbatim*}
chBar == [i \in 1..(p (-) c) |-> buf[(c (+) (i - 1)) % N]]
\end{verbatim*}
\end{popup}
\makeasciipopup