Paracol package: undefined environments

I got the LaTeX Error: Environment leftcolumn* undefined with the next MWE:

\documentclass{article}
\usepackage{paracol}

\begin{document}

\begin{leftcolumn*}
\subsection{%
Environments \texttt{leftcolumn} and\\
\texttt{rightcolumn}}
The environments |leftcolumn| and
|rightcolumn| (and their starred versions
with an optional argument) are available as
more convenient means than saying
|\begin{nthcolumn}{0}| to switch to the
left(most) column and ...
\begin{figure*}...\end{figure*}
\begin{figure}[t]...\end{figure}
\end{leftcolumn*}
\begin{rightcolumn}
source and a figure env
\end{rightcolumn}

\end{document}


It's very strange, so I don't know maybe if you compile it, it's will be okay. I'll show the evidence screenshot.

1 Answer

The documentation for the package does not make this very clear, but it seems that you need to enclose all of the environments it describes inside a paracol one:

\documentclass{article}
\usepackage{paracol}

\begin{document}
\begin{paracol}{2}
\begin{leftcolumn*}
\subsection{%
Environments \texttt{leftcolumn} and\\
\texttt{rightcolumn}}
The environments |leftcolumn| and
|rightcolumn| (and their starred versions
with an optional argument) are available as
more convenient means than saying
\verb|\begin{nthcolumn}{0}| to switch to the
left(most) column and ...
\begin{figure*}...\end{figure*}
\begin{figure}[t]...\end{figure}
\end{leftcolumn*}
\begin{rightcolumn}
source and a figure env
\end{rightcolumn}
\end{paracol}
\end{document}


(I've also fixed the verbatim code, which otherwise leads to an error.)