doc-src/extra.sty

tuned;

% extra.sty : Isabelle Manual extra macros for non-Springer version
%
\typeout{Document Style extra. Released 17 February 1994}

%%Euro-style date: 20 September 1955
\def\today{\number\day\space\ifcase\month\or
January\or February\or March\or April\or May\or June\or
July\or August\or September\or October\or November\or December\fi
\space\number\year}

%%Borrowed from alltt.sty, but leaves % as the comment character
\def\docspecials{\do\ \do\$\do\&%
  \do\#\do\^\do\^^K\do\_\do\^^A\do\~}

\def\alltt{\trivlist \item[]\if@minipage\else\vskip\parskip\fi
\leftskip\@totalleftmargin\rightskip\z@
\parindent\z@\parfillskip\@flushglue\parskip\z@
\@tempswafalse \def\par{\if@tempswa\hbox{}\fi\@tempswatrue\@@par}
\obeylines \tt \catcode``=13 \@noligs \let\do\@makeother \docspecials
 \frenchspacing\@vobeyspaces}

\let\endalltt=\endtrivlist

%Indented, boxed alltt environment; uses \small\tt font
%\leftmargini is LaTeX's first-level indentation for items (2.5em)
%@endparenv is LaTeX's trick for preventing indentation of next paragraph
%redefines \{ and \} to be in \tt font
\newenvironment{ttbox}{\par\nobreak\vskip-2pt
           \vbox\bgroup\footnotesize\begin{alltt}\chardef\{=`\{\chardef\}=`\}%
             \leftskip\leftmargini}%
        {\end{alltt}\egroup\vskip-7pt\@endparenv}
\newcommand\ttbreak{\end{ttbox}\vskip-10pt\begin{ttbox}}

%%%Put first chapter on odd page, with arabic numbering; like \cleardoublepage
\newcommand\clearfirst{\clearpage\ifodd\c@page\else
    \hbox{}\newpage\if@twocolumn\hbox{}\newpage\fi\fi
    \pagenumbering{arabic}}

%%%Ruled chapter headings 
\def\@rulehead#1{\hrule height1pt \vskip 14pt \Huge \bf 
   #1 \vskip 14pt\hrule height1pt}
\def\@makechapterhead#1{ { \parindent 0pt 
 \ifnum\c@secnumdepth >\m@ne \raggedleft\large\bf\@chapapp{} \thechapter \par 
 \vskip 20pt \fi \raggedright \@rulehead{#1} \par \nobreak \vskip 40pt } }

\def\@makeschapterhead#1{ { \parindent 0pt \raggedright 
 \@rulehead{#1} \par \nobreak \vskip 40pt } }