================================================================================
alltt environment
================================================================================
\begin{alltt}
$foo$ \(bar\) \emph{quux} ~ % wibble
\end{alltt}
--------------------------------------------------------------------------------
(document
  (text_env
    (begin (cs) (group (l) (name) (r)))
    (text)
    (latex_inline_math (cs) (math) (cs))
    (text)
    (emph
      (cs)
      (group (l) (text) (r)))
    (text)
    (end (cs) (group (l) (name) (r)))))