% Program texts -----------------------------------------

\newcommand{\programenvironment}{\programmode%
        \def\par{\leavevmode\endgraf}\obeylines\nobreak%
        \programmode}
\newcommand{\programinfig}{%
         \parindent 0em
         \nobreak\programenvironment}
\newcommand{\programmode}{\tt%
        \catcode`\_=12 \catcode`\?=12 \catcode`\.=12 \catcode`\,=12
        \catcode`\;=12 \catcode`\:=12 \catcode`\@=12 \catcode`\~=12
        \catcode`\#=12 \catcode`\&=12      % Added by PS 1991-06-17
        \catcode`\^=12                     % Added by PS 1992-11-03
        \obeyspaces\frenchspacing}%

\newenvironment{programintext}{\programenvironment}{}

\newlength{\programwidth}

\newenvironment{program}{%
        \setlength{\programwidth}{\textwidth}
        \addtolength{\programwidth}{-\leftmargin}
        \setlength{\partopsep}{0mm}\setlength{\topsep}{0mm}
        \begin{trivlist}\item[]
        \addtolength{\programwidth}{-\mathindent}
        \hspace*{\mathindent}\begin{minipage}{\programwidth}
        \vspace{1mm}
        \begin{programintext}
        }{\end{programintext}
        \vspace{1mm}
        \end{minipage}
        \end{trivlist}
        \noindent}

% The following is an environment for listing (long) programs in
% appendices etc., by PS 1991-06-17

\newcommand{\separatingline}{\noindent\rule[0.5\baselineskip]{\linewidth}{0.3mm}}

\newenvironment{longprogram}{%
        \parindent 0em
        \programenvironment
        \setlength{\baselineskip}{0.8\baselineskip}
        }{}

% What the following code does is not clear.  Maybe it makes Tex
% respect spaces and tabs in the source text, which is useful for
% program layout.

{\catcode`\^^I=\active \obeyspaces\global\def^^I{ }}
{\obeyspaces\global\let =\ } % let active space = control space
{\catcode`\`=\active \gdef`{\relax\lq}}