Meeting Pearls 3/Meeting_Pearls_III.iso/Pearls/texmf/inputs/distribs/verbatim/verbatim.doc

Text File | 1992-01-20 | 57.0 KB | 1,493 lines

\def\fileversion{v1.4i}
\def\filedate{92/01/20}
\def\docdate{91/12/18}

%% \CheckSum{446}
%% \CharacterTable
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%%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
%%   Digits        \0\1\2\3\4\5\6\7\8\9
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%%
%
%\iffalse   % this is a METACOMMENT !
%
%
%% Style-option `verbatim' to use with LaTeX v2.09
%% Copyright (C) 1989, 1990, 1991 by Rainer Sch\"opf, all rights reserved.
%
% Copying of this file is authorized only if either
% (1) you make absolutely no changes to your copy, including name, or
% (2) if you do make changes, you name it something other than
%     verbatim.doc.
% This restriction helps ensure that all styles developed here
% remain identical.
%
%
% Error reports please to: R. Sch\"opf
%                          Konrad-Zuse-Zentrum
%                          f\"ur Informationstechnik Berlin
%                          Heilbronner Str.\ 10
%                          D-1000 Berlin 31
%                          Federal Republic of Germany
%                  Email:  <[e-mail]>
%
%
%\fi
%
% \changes{v1.4g}{91/11/21}{Several improvements in the documentation.}
% \changes{v1.4f}{91/08/05}{Corrected bug in documentation.
%                           Found by Bernd Raichle.}
% \changes{v1.4e}{91/07/24}{Avoid reading this file twice.}
% \changes{v1.4d}{91/04/24}{`penalty`interlinepenalty added to
%                           definition of `par in `@verbatim.
%                           Necessary to avoid page breaks in
%                           the scope of a `samepage declaration.}
% \changes{v1.4c}{90/10/18}{Added `leavevmode to definition of
%       backquote macro.}
% \changes{v1.4b}{90/07/14}{Converted nearly all `verb's to \|...\|.}
% \changes{v1.4a}{90/04/04}{Added a number of percent characters
%       to suppress blank space at the end of some code lines.}
% \changes{v1.4}{90/03/07}{`verb rewritten.}
%
% \changes{v1.3a}{90/02/04}{Removed {\tt verbatimwrite} environment
%       from the code. Now only shown as an example.}
%
% \changes{v1.2g}{90/02/01}{Revised documentation.}
% \changes{v1.2e}{90/01/15}{Added `every@verbatim hook.}
% \changes{v1.2d}{89/11/29}{Use token register `@temptokena instead
%                           of macro `@tempb.}
% \changes{v1.2d}{89/11/29}{Use token register `verbatim@line instead
%                           of macro `@tempd.}
% \changes{v1.2b}{89/10/25}{`verbatimfile renamed to `verbatiminput.
%                           Suggested by Reinhard Wonneberger.}
%
% \changes{v1.1}{89/10/09}{Made the code more modular (as suggested by
%                          Chris Rowley):  introduced
%                          `verbatim@addtoline, etc.  Added
%                          `verbatimwrite environment.}
%
% \changes{v1.0e}{89/07/17}{Fixed bug in `verbatimfile (*-form
%         handling, discovered by Dirk Kreimer).}
% \changes{v1.0d}{89/05/16}{Revised documentation, fixed silly bug
%         in `verbatim@@@.}
% \changes{v1.0c}{89/05/12}{Added redefinition of `@sverb, change
%         in end-of-line handling.}
% \changes{v1.0b}{89/05/09}{Change in `verbatim@rescan.}
% \changes{v1.0a}{89/05/07}{Change in `verbatim@@testend.}
%
%
% \DoNotIndex{\ ,\!,\C,\[,\\,\],\^,\`,\{,\},\~}
% \DoNotIndex{\@M,\@empty,\@flushglue,\@gobble,\@ifstar,\@ifundefined}
% \DoNotIndex{\@namedef,\@spaces,\@tempa,\@tempb,\@tempc,\@tempd}
% \DoNotIndex{\@temptokena,\@totalleftmargin,\@warning,\active}
% \DoNotIndex{\aftergroup,\begingroup,\catcode,\char,\csname,\def,\do}
% \DoNotIndex{\docdate,\dospecials,\edef,\else,\endcsname,\endgroup}
% \DoNotIndex{\endtrivlist,\expandafter,\fi,\filedate,\fileversion}
% \DoNotIndex{\frenchspacing,\futurelet,\gdef,\if,\ifcat}
% \DoNotIndex{\ifx,\immediate,\item,\kern,\lccode,\leftskip,\let}
% \DoNotIndex{\lowercase,\next,\noexpand,\parfillskip,\parindent}
% \DoNotIndex{\parskip,\penalty,\relax,\rightskip,\space,\string,\the}
% \DoNotIndex{\toks@,\trivlist,\tt,\typeout,\vskip,\write,\z@}
%
%
% \title{A New Implementation of \LaTeX{}'s \\ {\tt verbatim}
%        and {\tt verbatim*} Environments\thanks{%
%        This file has version number \fileversion{} dated \filedate.
%        The documentation was last revised on \docdate.
%       }}
%
% \author{Rainer Sch\"opf$\,$\thanks{ Many thanks to Chris Rowley
%           from The Open University, UK, for looking this over,
%           making a lot of useful suggestions, and discovering bugs.
%           And many thanks to all the beta testers who tried this
%           style file out.}\\
%         Konrad-Zuse-Zentrum\\
%         f\"ur Informationstechnik Berlin\\
%         Heilbronner Str.\ 10\\
%         W-1000 Berlin 31\\
%         Federal Republic of Germany\\
%         Internet: {\tt [e-mail]}}
%
%
% \date{August 5, 1991}
%
% \markboth{Verbatim style option, version \fileversion, as of \filedate}
%          {Verbatim style option, version \fileversion, as of \filedate}
%
% \maketitle
%
% \begin{abstract}
%   This style option reimplements the \LaTeX{} {\tt verbatim} and
%   {\tt verbatim*} environments.
%   In addition it provides a {\tt comment} environment
%   that skips any commands or text between
%   |\begin{comment}|
%   and the next |\end{comment}|.
%   It also contains a redefinition of \LaTeX's |\verb| command
%   to better detect the omission of the closing delimiter.
% \end{abstract}
%
% \section{Usage notes}
%
% \let\docDescribeMacro\DescribeMacro
% \let\docDescribeEnv\DescribeEnv
% \def\DescribeMacro#1{}
% \def\DescribeEnv#1{}
% \LaTeX's {\tt verbatim} and {\tt verbatim*} environments
% have a few features that may give rise to problems. These are:
% \begin{itemize}
%   \item
%     Since \TeX{} has to read all the text between the
%     |\begin{verbatim}| and the |\end{verbatim}| before it can output
%     anything, long verbatim listings may overflow \TeX's memory.
%   \item
%     Due to the method used to detect the closing |\end{verbatim}|
%     (i.e.\ macro parameter delimiting) you cannot leave spaces
%     between the |\end| token and |{verbatim}|.
% \end{itemize}
% Whereas the last of these points can be considered
% only a minor nuisance the other one is a real limitation.
%
%
% \DescribeEnv{verbatim}
% \DescribeEnv{verbatim*}
% This style file contains a reimplementation of the {\tt verbatim}
% and {\tt verbatim*} environments which overcomes these restrictions.
% There is, however, one incompatibility between the old and the
% new implementations of these environments: the old version
% would treat text on the same line as the |\end{verbatim}|
% command as if it were on a line by itself.
% {\bf This new version will simply ignore it.}\footnote{This is
%   the price one has to pay for the removal of the old
%   {\tt verbatim} environment's size limitations.}
% It will, however, issue a warning message of the form
% \begin{verbatim}
%LaTeX warning: Characters dropped
%               after \end{verbatim*}!
%\end{verbatim}
% This is not a real problem since this text can easily be put
% on the next line without affecting the output.
%
% This new implementation also solves the second problem mentioned
% above: it is possible to leave spaces (but {\em not\/} end of line)
% between the |\end| and the |{verbatim}| or |{verbatim*}|:
% \begin{verbatim}
%\begin {verbatim*}
%   test
%   test
%\end {verbatim*}
%\end{verbatim}
%
% \DescribeEnv{comment}
% Additionally we introduce a {\tt comment} environment, with the
% effect that the text between |\begin{comment}| and |\end{comment}|
% is simply ignored, regardless of what it looks like.
% At first sight this seems to be quite different from the purpose
% of verbatim listing, but actually these two concepts turn out to be
% very similar.
% Both rely on the fact that the text between |\begin{...}| and
% |\end{...}| is read by \TeX{} without interpreting any commands or
% special characters.
% The remaining difference between {\tt verbatim} and {\tt comment} is
% only that the text is to be typeset in the former case and to be
% thrown away in the latter.
%
% \DescribeMacro{\verbatiminput}
% |\verbatiminput| is a command with one argument that inputs a file
% verbatim, i.e.\ the command |verbatiminput{xx.yy}|
% has the same effect as\\[2pt]
%   \hspace*{\MacroIndent}|\begin{verbatim}|\\
%   \hspace*{\MacroIndent}\meta{Contents of the file {\tt xx.yy}}\\
%   \hspace*{\MacroIndent}|\end{verbatim}|\\[2pt]
% This command has also a |*|-variant that prints spaces as \verb*+ +.
%
%
% \StopEventually{}
%
%
% \section{Interfaces for style file designers}
%
% The {\tt verbatim} environment of \LaTeX{} version 2.09 does not
% offer a good interface to programmers.
% In contrast, this style file provides a simple mechanism to
% implement similar features, the {\tt comment} environment provided
% here being an example of what can be done and how.
%
%
% \subsection{Simple examples}
%
% It is now possible to use the {\tt verbatim} environment to define
% environments of your own.
% E.g.,
%\begin{verbatim}
% \newenvironment{myverbatim}%
%   {\endgraf\noindent MYVERBATIM:%
%    \endgraf\verbatim}%
%   {\endverbatim}
%\end{verbatim}
% can be used afterwards like the {\tt verbatim} environment, i.e.
% \begin{verbatim}
%\begin {myverbatim}
%  test
%  test
%\end {myverbatim}
%\end{verbatim}
% Another way to use it is to write
% \begin{verbatim}
%\let\foo=\comment
%\let\endfoo=\endcomment
%\end{verbatim}
% and from that point on environment {\tt foo} is the same as the
% comment environment, i.e.\ everything inside its body is ignored.
%
% You may also add special commands after the |\verbatim| macro is
% invoked, e.g.
%\begin{verbatim}
%\newenvironment{myverbatim}%
%  {\verbatim\myspecialverbatimsetup}%
%  {\endverbatim}
%\end{verbatim}
% though you may want to learn about the hook |\every@verbatim| at
% this point.
% However, there are still a number of restrictions:
% \begin{enumerate}
%   \item
%     You must not use |\begin{verbatim}| inside a definition, e.g.
%     \begin{verbatim*}
%\newenvironment{myverbatim}%
%{\endgraf\noindent MYVERBATIM:%
% \endgraf\begin{verbatim}}%
%{\end{verbatim}}
%\end{verbatim*}
%     If you try this example, \TeX{} will report a
%     ``runaway argument'' error.
%     More generally, it is not possible to use
%     |\begin{verbatim}|\ldots\allowbreak|\end{verbatim}|
%     or the related environments in the definition of the new
%     environment.
%   \item
%     You can{\em not\/} use the {\tt verbatim} environment inside
%     user defined {\em commands}; e.g.,
% \changes{v1.4g}{91/11/21}{Corrcted wrong position of optional
%        argument to `newcommand. Discovered by Piet van Oostrum.}
%     \begin{verbatim*}
%\newcommand{\verbatimfile}[1]%
%{\begin{verbatim}%
% \input{#1}%
% \end{verbatim}}
%\end{verbatim*}
%     does {\em not\/} work; nor does
%     \begin{verbatim}
%\newcommand{\verbatimfile}[1]%
%  {\verbatim\input{#1}\endverbatim}
%\end{verbatim}
%   \item The name of the newly defined environment must not contain
%     characters with category code other than $11$ (letter) or
%     $12$ (other), or this will not work.
% \end{enumerate}
%
%
% \subsection{The interfaces}
%
% \DescribeMacro{\verbatim@font}
% Let us start with the simple things.
% Sometimes it may be necessary to use a special typeface for your
% verbatim text, or perhaps the usual computer modern typewriter shape
% in a reduced size.
%
% You may select this by redefining the macro |\verbatim@font|.
% This macro is executed at the beginning of every verbatim text to
% select the font shape.
% Do not use it for other purposes; if you find yourself abusing this
% you may want to read about the |\every@verbatim| hook below.
%
% By default, |\verbatim@font| switches to the typewriter font and
% disables the |?`| and |!`| ligatures.
%
%
% \DescribeMacro{\every@verbatim}
% \DescribeMacro{\addto@hook}
% There is a hook (i.e.\ a token register) called |\every@verbatim|
% whose contents are inserted into \TeX's mouth just before every
% verbatim text.
% Please use the |\addto@hook| macro to add something to this hook.
% It is used as follows:\\[2pt]
% \hspace*{\MacroIndent}|\addto@hook|\meta{name of the hook}\\
% \hspace*{\MacroIndent}\hspace*{\MacroIndent}^^A
%  |{|\meta{commands to be added}|}|
% \vspace*{2pt}
%
%
%
% \DescribeMacro{\verbatim@start}
% After all specific setup, like switching of category codes, has been
% done, the |\verbatim@start|
% \newpage
% \onecolumn
% \begin{multicols}{2}
% \noindent
% macro is called.
% This starts the main loop of the scanning mechanism implemented here.
% Any other environment that wants to make use of this feature should
% call this macro as its last action.
%
%
% \DescribeMacro{\verbatim@startline}
% \DescribeMacro{\verbatim@addtoline}
% \DescribeMacro{\verbatim@processline}
% \DescribeMacro{\verbatim@finish}
% These are the things that concern the start of a verbatim
% environment.
% Once this (and other) setup has been done, the code in this style
% file reads and processes characters from the input stream in the
% following way:
% \begin{enumerate}
%   \item Before it starts to read the first character of an input line
%     the macro |\verbatim@startline| is called.
%   \item After some characters have been read, the macro
%     |\verbatim@addtoline| is called with these characters as its only
%     argument.
%     This may happen several times per line (when an |\end| command is
%     present on the line in question).
%   \item When the end of the line is reached, the macro
%     |\verbatim@processline| is called to process the characters that
%     |\verbatim@addtoline| has accumulated.
%   \item Finally, there is the macro |\verbatim@finish| that is called
%     just before the environment is ended by a call to the |\end|
%      macro.
% \end{enumerate}
%
%
% To make this clear consider the standard {\tt verbatim} environment.
% In this case the three macros above are defined as follows:
% \begin{enumerate}
%   \item |\verbatim@startline| clears the character buffer
%     (a token register).
%   \item |\verbatim@addtoline| adds its argument to the character
%     buffer.
%   \item |\verbatim@processline| typesets the characters accumulated
%     in the buffer.
% \end{enumerate}
% With this it is very simple to implement the {\tt comment}
% environment:
% in this case |\verbatim@startline| and |\verbatim@processline| are
% no-ops whereas |\verbatim@addtoline| discards its argument.
%
%
% Another possibility is to define a variant of the |verbatim|
% environment that prints line numbers in the left margin.
% Assume that this would be done by a counter called |VerbatimLineNo|.
% Assuming that this counter was initialized properly by the
% environment, |\verbatim@processline| would be defined in this case as
% \begin{verbatim}
%\def\verbatim@processline{%
%  \addtocounter{VerbatimLineNo}{1}%
%  \leavevmode
%  \llap{\theVerbatimLineNo
%        \ \hskip\@totalleftmargin}%
%  \the\verbatim@line\par}
%\end{verbatim}
%
% As a final nontrivial example we describe the definition of an
% environment called {\tt verbatimwrite}.
% It writes all text in its body to a file the name of which it is
% given as an argument.
% We assume that a stream number called |\verbatim@out| has already
% been reserved by means of the |\newwrite| macro.
%
% Let's begin with the definition of the macro |\verbatimwrite|.
% \begin{verbatim}
%\def\verbatimwrite#1{%
%\end{verbatim}
% First we call |\@bsphack| so that this environment does not influence
% the spacing.
% Then we open the file and set the category codes of all special
% characters:
% \begin{verbatim}
%  \@bsphack
%  \immediate\openout \verbatim@out #1
%  \let\do\@makeother\dospecials
%  \catcode`\^^M\active
%\end{verbatim}
% The default definitions of the macros
% \begin{verbatim}
%  \verbatim@startline
%  \verbatim@addtoline
%  \verbatim@finish
%\end{verbatim}
% are also used in this environment.
% Only the macro |\verbatim@processline| has to be changed before
% |\verbatim@start| is called:
% \begin{verbatim}
%  \def\verbatim@processline{%
%    \immediate\write\verbatim@out
%      {\the\verbatim@line}}%
%  \verbatim@start}
%\end{verbatim}
% The definition of |\endverbatimwrite| is very simple:
% we close the stream and call |\@esphack| to get the spacing right.
% \begin{verbatim}
%\def\endverbatimwrite{%
%  \immediate\closeout\verbatim@out
%  \@esphack}
%\end{verbatim}
% \end{multicols}
%
% \newpage
% \SelfDocumenting
%
% \section{The implementation}
%
% \let\DescribeMacro\docDescribeMacro
% \let\DescribeEnv\docDescribeEnv
%
% \changes{v1.4e}{91/07/24}{Avoid reading this file twice.}
% The very first thing we do is to ensure that this file is not read
% in twice. To this end we check whether the macro |\verbatim@@@| is
% defined. If so, we just stop reading this file.
%    \begin{macrocode}
\@ifundefined{verbatim@@@}{}{\endinput}
%    \end{macrocode}
%
% We use a mechanism similar to the one implemented for the
% |\comment|\ldots\allowbreak|\endcomment| macro in \AmSTeX:
% We input one line at a time and check if it contains the |\end{...}|
% tokens.
% Then we can decide whether we have reached the end of the verbatim
% text, or must continue.
%
% As always we begin by identifying the latest version of this file on
% the VDU and in the transcript file.
%    \begin{macrocode}
\typeout{Style-Option: `verbatim'
   \fileversion \space <\filedate>  (RmS)}
\typeout{English Documentation
   \@spaces \@spaces \space <\docdate>  (RmS)}
%    \end{macrocode}
%
%
% \subsection{Preliminaries}
%
% \begin{macro}{\addto@hook}
% \changes{v1.2e}{90/01/15}{`addto@hook added.}
%    We begin by defining a macro that adds tokens to a hook.
%    The first argument is supposed to be a token register, the
%    second consists of arbitrary \TeX{} text.
%    \begin{macrocode}
\def\addto@hook#1#2{#1\expandafter{\the#1#2}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\every@verbatim}
% \changes{v1.2e}{90/01/15}{`every@verbatim hook added.}
%    The hook (i.e.\ token register) |\every@verbatim|
%    is initialized to \meta{empty}.
%    \begin{macrocode}
\newtoks\every@verbatim
\every@verbatim={}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@makeother}
% \changes{v1.1a}{89/10/16}{`@makeother added.}
%    |\@makeother| takes as argument a character and changes
%    its category code to $12$ (other).
%    \begin{macrocode}
\def\@makeother#1{\catcode`#112\relax}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@vobeyspaces}
% \changes{v1.1a}{89/10/16}{`@vobeyspaces added.}
%    The macro |\@vobeyspaces| causes spaces in the input
%    to be printed as spaces in the output.
%    \begin{macrocode}
\begingroup
 \catcode`\ =\active%
\gdef\@vobeyspaces{\catcode`\ \active\let \@xobeysp}%
\endgroup
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@xobeysp}
% \changes{v1.1a}{89/10/16}{`@xobeysp added.}
%    The macro |\@xobeysp| produces exactly one space in
%    the output, protected against breaking just before it.
%    (|\@M| is an abbreviation for the number $10000$.)
%    \begin{macrocode}
\def\@xobeysp{\leavevmode\penalty\@M\ }
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\verbatim@line}
% \changes{v1.2d}{89/11/29}{Introduced token register `verbatim@line.}
%    We use a newly defined token register called |\verbatim@line|
%    that will be used as the character buffer.
%    \begin{macrocode}
\newtoks\verbatim@line
%    \end{macrocode}
% \end{macro}
%
% The following four macros are defined globally in a way suitable for
% the {\tt verbatim} and {\tt verbatim*} environments.
% \begin{macro}{\verbatim@startline}
% \begin{macro}{\verbatim@addtoline}
% \begin{macro}{\verbatim@processline}
%    |\verbatim@startline| initializes processing of a line
%    by emptying the character buffer (|\verbatim@line|).
%    \begin{macrocode}
\def\verbatim@startline{\verbatim@line{}}
%    \end{macrocode}
%    |\verbatim@addtoline| adds the tokens in its argument
%    to our buffer register |\verbatim@line| without expanding
%    them.
%    \begin{macrocode}
\def\verbatim@addtoline#1{%
  \verbatim@line\expandafter{\the\verbatim@line#1}}
%    \end{macrocode}
%    Processing a line inside a {\tt verbatim} or {\tt verbatim*}
%    environment means printing it.
% \changes{v1.2c}{89/10/31}{Changed `@@par to `par in
%    `verbatim@processline.  Removed `leavevmode and `null
%    (i.e.\ the empty `hbox).}
%    Ending the line means that we have to begin a new paragraph.
%    We use |\par| for this purpose.  Note that |\par|
%    is redefined in |\@verbatim| to force \TeX{} into horizontal
%    mode and to insert an empty box so that empty lines in the input
%    do appear in the output.
% \changes{v1.2f}{90/01/31}{Removed `verbatim@startline.}
%    \begin{macrocode}
\def\verbatim@processline{\the\verbatim@line\par}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\verbatim@finish}
%    As a default, |\verbatim@finish| processes the remaining
%    characters.
%    When this macro is called we are facing the following problem:
%    when the |\end{verbatim}|
%    command is encountered |\verbatim@processline| is called
%    to process the characters preceding the command on the same
%    line.  If there are none, an empty line would be output if we
%    did not check for this case.
%
%    If the line is empty |\the\verbatim@line| expands to
%    nothing.  To test this we use a trick similar to that on p.\ 376
%    of the \TeX{}book, but with |$|\ldots|$| instead of
%    the |!| tokens.  These tokens can never have the same
%    category code as those appearing in the token register
%    |\verbatim@line| where |$| characters were read with
%    category code $12$ (other).
%    Note that |\ifcat| expands the following tokens so that
%    |\the\verbatim@line| is replaced by the accumulated
%    characters
% \changes{v1.2d}{89/11/29}{Changed `ifx to `ifcat test.}
% \changes{v1.1b}{89/10/18}{Corrected bug in if test (found by Chris).}
%    \begin{macrocode}
\def\verbatim@finish{\ifcat$\the\verbatim@line$\else
  \verbatim@processline\fi}
%    \end{macrocode}
% \end{macro}
%
%
% \subsection{The {\tt verbatim} and {\tt verbatim*} environments}
%
% \begin{macro}{\verbatim@font}
% \changes{v1.2f}{90/01/31}{`@lquote macro removed.}
% \changes{v1.1b}{89/10/18}{`@noligs removed.  Code inserted
%                           directly into `verbatim@font.}
% \changes{v1.1a}{89/10/16}{`verbatim@font added.}
% \changes{v1.1a}{89/10/16}{`@noligs added.}
% \changes{v1.1a}{89/10/16}{`@lquote added.}
%    We start by defining the macro |\verbatim@font| that is
%    to select the font and to set font-dependent parameters.
%    For the default computer modern
%    typewriter font ({\tt cmtt}) we have to avoid the
%    ligatures !` and ?` (as produced by |!`| and |?`|).
%    We do this by making the backquote |`| character active
%    and defining it to insert an
%    explicit kern before the backquote character.
%    If the backquote character is the first character of the
%    a {\tt verbatim} environment, \TeX{} is still in vertical
%    mode.
%    This means that the |\kern| command is processed in vertical mode
%    and treated as a vertical kern.
%    To avoid this, we use the |\leavevmode| macro.
%    While the backquote character is active we cannot use it in a
%    construction like
%    |\catcode`|\meta{char}|=|\meta{number}.
%    Instead we use the ASCII code of this character ($96$).
% \changes{v1.2f}{90/01/31}{`@lquote macro removed.}
% \changes{v1.4c}{90/10/18}{Added `leavevmode.}
%    \begin{macrocode}
\begingroup
 \catcode`\`=\active
 \gdef\verbatim@font{\tt \catcode96\active
   \def`{\leavevmode\kern\z@\char96 }}
\endgroup
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\@verbatim}
% \changes{v1.1a}{89/10/16}{`@verbatim added.}
%    The macro |\@verbatim| sets up things properly.
%    First of all, the tokens of the |\every@verbatim| hook
%    are inserted.
%    Then a {\tt trivlist} environment is started and its first
%    |\item| command inserted.
%    Each line of the {\tt verbatim} or {\tt verbatim*}
%    environment will be treated as a separate paragraph.
% \changes{v1.2e}{90/01/15}{Added `every@verbatim hook.}
%    \begin{macrocode}
\def\@verbatim{\the\every@verbatim
  \trivlist \item[]%
%    \end{macrocode}
% \changes{v1.3c}{90/02/26}{Removed extra vertical space.
%           Suggested by Frank Mittelbach.}
%    The paragraph parameters are set appropriately:
%    left and right margins, paragraph indentation, the glue to
%    fill the last line and the vertical space between paragraphs.
%    This has to be zero since we do not want to add extra space
%    between lines.
%    \begin{macrocode}
  \leftskip\@totalleftmargin\rightskip\z@
  \parindent\z@\parfillskip\@flushglue\parskip\z@
%    \end{macrocode}
% \changes{v1.1b}{89/10/18}{Added resetting of `parshape
%                           if at beginning of a list.
%                           (Problem pointed out by Chris.)}
%    There's one point to make here:
%    the {\tt list} environment uses \TeX's |\parshape|
%    primitive to get a special indentation for the first line
%    of the  list.
%    If the list begins with a {\tt verbatim} environment
%    this |\parshape| is still in effect.
%    Therefore we have to reset this internal parameter explicitly.
%    We could do this by assigning $0$ to |\parshape|.
%    However, there is a simpler way to achieve this:
%    we simply tell \TeX{} to start a new paragraph.
%    As is explained on p.~103 of the \TeX{}book, this resets
%    |\parshape| to zero.
% \changes{v1.1c}{89/10/19}{Replaced explicit resetting of `parshape
%                           by `@@par.}
%    \begin{macrocode}
  \@@par
%    \end{macrocode}
%    We now ensure that |\par| has the correct definition,
%    namely to force \TeX{} into horizontal mode
%    and to include an empty box.
%    This is to ensure that empty lines do appear in the output.
%    Afterwards, we insert the |\interlinepenalty| since \TeX{}
%    does not add a penalty between paragraphs (here: lines)
%    by its own initiative. Otherwise a |verbatim| environment
%    could be broken across pages even if a |\samepage|
%    declaration were present.
% \changes{v1.4d}{91/04/24}{`penalty`interlinepenalty added.
%                           Necessary to avoid page breaks in
%                           the scope of a `samepage declaration.}
% \changes{v1.2c}{89/10/31}{Definition of `par added.
%                           Ensures identical behaviour for
%                           verbatim and `verbatiminput.
%                           Problem pointed out by Chris.}
%    \begin{macrocode}
  \def\par{\leavevmode\null\@@par\penalty\interlinepenalty}%
%    \end{macrocode}
%    Now we call |\obeylines| to make the end of line character
%    active,
%    \begin{macrocode}
  \obeylines
%    \end{macrocode}
%    switch to the font to be used,
%    \begin{macrocode}
  \verbatim@font
%    \end{macrocode}
%    and change the category code of all special characters
%    to $12$ (other).
%    \begin{macrocode}
  \let\do\@makeother \dospecials}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\verbatim}
% \begin{macro}{\verbatim*}
%    Now we define the toplevel macros.
%    |\verbatim| is slightly changed:
%    after setting up things properly it calls
%    |\verbatim@start|.
%    \begin{macrocode}
\def\verbatim{\@verbatim \frenchspacing\@vobeyspaces\verbatim@start}
%    \end{macrocode}
%    |\verbatim*| is defined accordingly.
%    \begin{macrocode}
\@namedef{verbatim*}{\@verbatim\verbatim@start}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\endverbatim}
% \begin{macro}{\endverbatim*}
%    To end the {\tt verbatim} and {\tt verbatim*}
%    environments it is only necessary to finish the
%    {\tt trivlist} environment started in |\@verbatim|.
%    \begin{macrocode}
\let\endverbatim=\endtrivlist
\expandafter\let\csname endverbatim*\endcsname =\endtrivlist
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
%
% \subsection{The {\tt comment} environment}
%
% \begin{macro}{\comment}
% \begin{macro}{\endcomment}
% \changes{v1.1c}{89/10/19}{Added `@bsphack/`@esphack to the {\tt
%              comment} environment.  Suggested by Chris Rowley.}
%    The |\comment| macro is similar to |\verbatim*|.
%    However, we do not need to switch fonts or set special
%    formatting parameters such as |\parindent| or |\parskip|.
%    We need only set the category code of all special characters
%    to $12$ (other) and that of |^^M| (the end of line character)
%    to $13$ (active).
%    The latter is needed for macro parameter delimiter matching in
%    the internal macros defined below.
%    In contrast to the default definitions used by the
%    |\verbatim| and |\verbatim*| macros,
%    we define |\verbatim@addtoline| to throw away its argument
%    and |\verbatim@processline|, |\verbatim@startline|,
%    and |\verbatim@finish| to act as no-ops.
%    Then we call |\verbatim@|.
%    But the first thing we do is to call |\@bsphack| so that
%    this environment has no influence whatsoever upon the spacing.
% \changes{v1.1c}{89/10/19}{Changed `verbatim@start to
%                           `verbatim@.  Suggested by Chris Rowley.}
% \changes{v1.1c}{89/10/19}{`verbatim@startline and
%                           `verbatim@finish are now
%                           also redefined to do nothing.}
%    \begin{macrocode}
\def\comment{\@bsphack
             \let\do\@makeother\dospecials\catcode`\^^M\active
             \let\verbatim@startline\relax
             \let\verbatim@addtoline\@gobble
             \let\verbatim@processline\relax
             \let\verbatim@finish\relax
             \verbatim@}
%    \end{macrocode}
%    |\endcomment| is very simple: it only calls
%    |\@esphack| to take care of the spacing.
%    The |\end| macro closes the group and therefore takes care
%    of restoring everything we changed.
%    \begin{macrocode}
\let\endcomment=\@esphack
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
%
%
% \subsection{The main loop}
%
% Here comes the tricky part:
% During the definition of the macros we need to use the special
% characters |\|, |{|, and |}| not only with their
% normal category codes,
% but also with category code $12$ (other).
% We achieve this by the following trick:
% first we tell \TeX{} that |\|, |{|, and |}|
% are the lowercase versions of |!|, |[|, and |]|.
% Then we replace every occurrence of |\|, |{|, and |}|
% that should be read with category code $12$ by |!|, |[|,
% and |]|, respectively,
% and give the whole list of tokens to |\lowercase|,
% knowing that category codes are not altered by this primitive!
%
% But first we have ensure that
% |!|, |[|, and |]| themselves have
% the correct category code!
% \changes{v1.3b}{90/02/07}{Introduced `vrb@catcodes instead
%                  of explicit setting of category codes.}
% To allow special settings of these codes we hide their setting in
% the macro |\vrb@catcodes|.  If it is already defined our new
% definition is skipped.
%    \begin{macrocode}
\@ifundefined{vrb@catcodes}%
  {\def\vrb@catcodes{%
     \catcode`\!12\catcode`\[12\catcode`\]12}}{}
%    \end{macrocode}
% This allows the use of this code for applications where other
% category codes are in effect.
%
% We start a group to keep the category code changes local.
%    \begin{macrocode}
\begingroup
 \vrb@catcodes
 \lccode`\!=`\\ \lccode`\[=`\{ \lccode`\]=`\}
%    \end{macrocode}
% \changes{v1.2f}{90/01/31}{Code for TABs removed.}
%    We also need the end-of-line character |^^M|,
%    as an active character.
%    If we were to simply write |\catcode`\^^M=\active|
%    then we would get an unwanted active end of line character
%    at the end of every line of the following macro definitions.
%    Therefore we use the same trick as above:
%    we write a tilde |~| instead of |^^M| and
%    pretend that the
%    latter is the lowercase variant of the former.
%    Thus we have to ensure now that the tilde character has
%    category code $13$ (active).
%    \begin{macrocode}
 \catcode`\~=\active \lccode`\~=`\^^M
%    \end{macrocode}
%    The use of the |\lowercase| primitive leads to one problem:
%    the uppercase character `|C|' needs to be used in the
%    code below and its case must be preserved.
%    So we add the command:
%    \begin{macrocode}
 \lccode`\C=`\C
%    \end{macrocode}
%    Now we start the token list passed to |\lowercase|.
%    \begin{macrocode}
 \lowercase{%
%    \end{macrocode}
% Since this is done in a group all macro definitions are executed
% globally.
% \begin{macro}{\verbatim@start}
%    The purpose of |\verbatim@start| is to check whether there
%    are any characters on the same line as the |\begin{verbatim}|
%    and to pretend that they were on a line by themselves.
%    On the other hand, if there are no characters remaining
%    on the current line we shall just find an end of line character.
%    |\verbatim@start| performs its task by first grabbing the
%    following character (its argument).
%    This argument is then compared to an active |^^M|,
%    the end of line character.
%    \begin{macrocode}
    \gdef\verbatim@start#1{%
      \verbatim@startline
      \if\noexpand#1\noexpand~%
%    \end{macrocode}
%    If this is true we transfer control to |\verbatim@|
%    to process the next line.  We use
%    |\next| as the macro which will continue the work.
%    \begin{macrocode}
        \let\next\verbatim@
%    \end{macrocode}
%    Otherwise, we define |\next| to expand to a call
%    to |\verbatim@| followed by the character just
%    read so that it is reinserted into the text.
%    This means that those characters remaining on this line
%    are handled as if they formed a line by themselves.
%    \begin{macrocode}
      \else \def\next{\verbatim@#1}\fi
%    \end{macrocode}
%    Finally we call |\next|.
%    \begin{macrocode}
      \next}%
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\verbatim@}
%    The three macros |\verbatim@|, |\verbatim@@|,
%    and |\verbatim@@@| form the ``main loop'' of the
%    {\tt verbatim} environment.
%    The purpose of |\verbatim@| is to read exactly one line
%    of input.
%    |\verbatim@@| and |\verbatim@@@| work together to
%    find out whether the four characters
%    |\end| (all with category code $12$ (other)) occur in that
%    line.
%    If so, |\verbatim@@@| will call
%    |\verbatim@test| to check whether this |\end| is
%    part of |\end{verbatim}| and will terminate the environment
%    if this is the case.
%    Otherwise we continue as if nothing had happened.
%    So let's have a look at the definition of |\verbatim@|:
% \changes{v1.1a}{89/10/16}{Replaced `verbatim@@@ by `@nil.}
%    \begin{macrocode}
    \gdef\verbatim@#1~{\verbatim@@#1!end\@nil}%
%    \end{macrocode}
%    Note that the |!| character will have been replaced by a
%    |\| with category code $12$ (other) by the |\lowercase|
%    primitive governing this code before the definition of this
%    macro actually takes place.
%    That means that
%    it takes the line, puts |\end| (four character tokens)
%    and |\@nil| (one control sequence token) as a
%    delimiter behind it, and
%    then calls |\verbatim@@|.
% \end{macro}
%
% \begin{macro}{\verbatim@@}
%    |\verbatim@@| takes everything up to the next occurrence of
%    the four characters |\end| as its argument.
%    \begin{macrocode}
    \gdef\verbatim@@#1!end{%
%    \end{macrocode}
%    That means: if they do not occur in the original line, then
%    argument |#1| is the
%    whole input line, and |\@nil| is the next token
%    to be processed.
%    However, if the four characters |\end| are part of the
%    original line, then
%    |#1| consists of the characters in front of |\end|,
%    and the next token is the following character (always remember
%    that the line was lengthened by five tokens).
%    Whatever |#1| may be, it is verbatim text,
%    so |#1| is added to the line currently built.
%    \begin{macrocode}
       \verbatim@addtoline{#1}%
%    \end{macrocode}
%    The next token in the input stream
%    is of special interest to us.
%    Therefore |\futurelet| defines |\next| to be equal
%    to it before calling |\verbatim@@@|.
%    \begin{macrocode}
       \futurelet\next\verbatim@@@}%
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\verbatim@@@}
% \changes{v1.1a}{89/10/16}{Replaced `verbatim@@@ by
%                           `@nil where used as delimiter.}
%    |\verbatim@@@| will now read the rest of the tokens on
%    the current line,
%    up to the final |\@nil| token.
%    \begin{macrocode}
    \gdef\verbatim@@@#1\@nil{%
%    \end{macrocode}
%    If the first of the above two cases occurred, i.e.\ no
%    |\end| characters were on that line, |#1| is empty
%    and |\next| is equal to |\@nil|.
%    This is easily checked.
%    \begin{macrocode}
       \ifx\next\@nil
%    \end{macrocode}
%    If so, this was a simple line.
%    We finish it by processing the line we accumulated so far.
%    Then we prepare to read the next line.
% \changes{v1.2f}{90/01/31}{Added `verbatim@startline.}
%    \begin{macrocode}
         \verbatim@processline
         \verbatim@startline
         \let\next\verbatim@
%    \end{macrocode}
%    Otherwise we have to check what follows these |\end|
%    tokens.
%    \begin{macrocode}
       \else
%    \end{macrocode}
%    Before we continue, it's a good idea to stop for a moment
%    and remember where we are:
%    We have just read the four character tokens |\end|
%    and must now check whether the name of the environment (surrounded
%    by braces) follows.
%    To this end we define a macro called |\@tempa|
%    that reads exactly one character and decides what to do next.
%    This macro should do the following: skip spaces until
%    it encounters either a left brace or the end of the line.
%    But it is important to remember which characters are skipped.
%    The |\end|\meta{optional spaces}|{| characters
%    may be part of the verbatim text, i.e.\ these characters
%    must be printed.
%
%    Assume for example that the current line contains
%    \begin{verbatim*}
%      \end {AVeryLongEnvironmentName}
%\end{verbatim*}
%    As we shall soon see, the scanning mechanism implemented here
%    will not find out that this is text to be printed until
%    it has read the right brace.
%    Therefore we need a way to accumulate the characters read
%    so that we can reinsert them if necessary.
%    The token register |\@temptokena| is used for this purpose.
%
%    Before we do this we have to get rid of the superfluous
%    |\end| tokens at the end of the line.
%    To this end we define a temporary macro whose argument
%    is delimited by |\end\@nil| (four character tokens
%    and one control sequence token)
%    and use it on the rest of the line,
%    after appending a |\@nil| token to it.
%    This token can never appear in |#1|.
%    We use the following definition of
%    |\@tempa| to store the rest of the line (after the first
%    |\end|) in token register |\toks@|
%    which we shall use again in a moment.
%    \begin{macrocode}
         \def\@tempa##1!end\@nil{\toks@{##1}}%
           \@tempa#1\@nil
%    \end{macrocode}
%    We mentioned already that we use token register
%    |\@temptokena|
%    to remember the characters we skip, in case we need them again.
%    We initialize this with the |\end| we have thrown away
%    in the call to |\@tempa|.
%    \begin{macrocode}
         \@temptokena{!end}%
%    \end{macrocode}
%    We shall now call |\verbatim@test|
%    to process the characters
%    remaining on the current line.
%    But wait a moment: we cannot simply call this macro
%    since we have already read the whole line.
%    We stored its characters in token register |\toks@|.
%    Therefore we use the following |\edef| to insert them again
%    after the |\verbatim@test| token.
%    A |^^M| character is appended to denote the end of the line.
% \changes{v1.2}{89/10/20}{Taken local definition of `@tempa out of
%                          `verbatim@@@ and introduced
%                          `verbatim@test instead.}
%    \begin{macrocode}
         \edef\next{\noexpand\verbatim@test\the\toks@\noexpand~}%
%    \end{macrocode}
%    That's almost all, but we still have to
%    now call |\next| to do the work.
%    \begin{macrocode}
       \fi \next}%
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\verbatim@test}
% \changes{v1.2}{89/10/20}{Introduced `verbatim@test.}
%    We define |\verbatim@test| to investigate every token
%    in turn.
%    \begin{macrocode}
 \gdef\verbatim@test#1{%
%    \end{macrocode}
%    First of all we set |\next| equal to |\verbatim@test|
%    in case this macro must call itself recursively in order to
%    skip spaces.
%    \begin{macrocode}
           \let\next\verbatim@test
%    \end{macrocode}
%    We have to distinguish four cases:
%    \begin{enumerate}
%      \item The next token is a |^^M|, i.e.\ we reached
%            the end of the line.  That means that nothing
%            special was found.
%            Note that we use |\if| for the following
%            comparisons so that the category code of the
%            characters is irrelevant.
%    \begin{macrocode}
           \if\noexpand#1\noexpand~%
%    \end{macrocode}
%            We add the characters accumulated in token register
%            |\@temptokena| to the current line.  Since
%            |\verbatim@addtoline| does not expand its argument,
%            we have to do the expansion at this point.  Then we
%            |\let| |\next| equal to |\verbatim@|
%            to prepare to read the next line.
% \changes{v1.2f}{90/01/31}{Added `verbatim@startline.}
%    \begin{macrocode}
             \expandafter\verbatim@addtoline
               \expandafter{\the\@temptokena}%
             \verbatim@processline
             \verbatim@startline
             \let\next\verbatim@
%    \end{macrocode}
%      \item A space character follows.
%            This is allowed, so we add it to |\@temptokena|
%            and continue.
%    \begin{macrocode}
           \else \if\noexpand#1
             \@temptokena\expandafter{\the\@temptokena#1}%
%    \end{macrocode}
% \changes{v1.2f}{90/01/31}{Code for TABs removed.}
%      \item An open brace follows.
%            This is the most interesting case.
%            We must now collect characters until we read the closing
%            brace and check whether they form the environment name.
%            This will be done by |\verbatim@testend|, so here
%            we let |\next| equal this macro.
%            Again we will process the rest of the line, character
%            by character.
% \changes{v1.2}{89/10/20}{Moved the initialization of
%                          `@tempc from `verbatim@testend into
%                          `verbatim@test.}
%            The characters forming the name of the environment will
%            be accumulated in |\@tempc|.
%            We initialize this macro to expand to nothing.
% \changes{v1.3b}{90/02/07}{`noexpand added.}
%    \begin{macrocode}
           \else \if\noexpand#1\noexpand[%
             \let\@tempc\@empty
             \let\next\verbatim@testend
%    \end{macrocode}
%            Note that the |[| character will be a |{| when
%            this macro is defined.
%      \item Any other character means that the |\end| was part
%            of the verbatim text.
%            Add the characters to the current line and prepare to call
%            |\verbatim@| to process the rest of the line.
%  \changes{v1.0f}{89/10/09}{Fixed `end `end bug
%                            found by Chris Rowley}
%    \begin{macrocode}
           \else
             \expandafter\verbatim@addtoline
               \expandafter{\the\@temptokena}%
             \def\next{\verbatim@#1}%
           \fi\fi\fi
%    \end{macrocode}
%    \end{enumerate}
%    The last thing this macro does is to call |\next|
%    to continue processing.
%    \begin{macrocode}
           \next}%
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\verbatim@testend}
%    |\verbatim@testend| is called when
%    |\end|\meta{optional spaces}|{| was seen.
%    Its task is to scan everything up to the next |}|
%    and to call |\verbatim@@testend|.
%    If no |}| is found it must reinsert the characters it read
%    and return to |\verbatim@|.
%    The following definition is similar to that of
%    |\verbatim@test|:
%    it takes the next character and decides what to do.
% \changes{v1.2}{89/10/20}{Removed local definition of `@tempa from
%                          `verbatim@testend which now
%                          does the work itself.}
%    \begin{macrocode}
    \gdef\verbatim@testend#1{%
%    \end{macrocode}
%    Again, we have four cases:
%    \begin{enumerate}
%      \item |^^M|: As no |}| is found in the current line,
%            add the characters to the buffer.  To avoid a
%            complicated construction for expanding
%            |\@temptokena|
%            and |\@tempc| we do it in two steps.  Then we
%            continue with |\verbatim@| to process the
%            next line.
% \changes{v1.2f}{90/01/31}{Added `verbatim@startline.}
%    \begin{macrocode}
         \if\noexpand#1\noexpand~%
           \expandafter\verbatim@addtoline
             \expandafter{\the\@temptokena[}%
           \expandafter\verbatim@addtoline
             \expandafter{\@tempc}%
           \verbatim@processline
           \verbatim@startline
           \let\next\verbatim@
%    \end{macrocode}
%      \item |}|: Call |\verbatim@@testend| to check
%            if this is the right environment name.
% \changes{v1.3b}{90/02/07}{`noexpand added.}
%    \begin{macrocode}
         \else\if\noexpand#1\noexpand]%
           \let\next\verbatim@@testend
%    \end{macrocode}
%  \changes{v1.0f}{89/10/09}{Introduced check for {\tt\bslash} to fix
%                            single brace bug found by Chris Rowley}
%      \item |\|: This character must not occur in the name of
%            an environment.  Thus we stop collecting characters.
%            In principle, the same argument would apply to other
%            characters as well, e.g., |{|.
%            However, |\| is a special case, since it may be
%            the first character of |\end|.  This means that
%            we have to look again for
%            |\end{|\meta{environment name}|}|.
%            Note that we prefixed the |!| by a |\noexpand|
%            primitive, to protect ourselves against it being an
%            active character.
% \changes{v1.3b}{90/02/07}{`noexpand added.}
%    \begin{macrocode}
         \else\if\noexpand#1\noexpand!%
           \expandafter\verbatim@addtoline
             \expandafter{\the\@temptokena[}%
           \expandafter\verbatim@addtoline
             \expandafter{\@tempc}%
           \def\next{\verbatim@!}%
%    \end{macrocode}
%      \item Any other character: collect it and continue.
%            We cannot use |\edef| to define |\@tempc|
%            since its replacement text might contain active
%            character tokens.
%    \begin{macrocode}
         \else \expandafter\def\expandafter\@tempc\expandafter
           {\@tempc#1}\fi\fi\fi
%    \end{macrocode}
%    \end{enumerate}
%    As before, the macro ends by calling itself, to
%    process the next character if appropriate.
%    \begin{macrocode}
         \next}%
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\verbatim@@testend}
%    Unlike the previous macros |\verbatim@@testend| is simple:
%    it has only to check if the |\end{|\ldots|}|
%    matches the corresponding |\begin{|\ldots|}|.
%    \begin{macrocode}
    \gdef\verbatim@@testend{%
%    \end{macrocode}
%    We use |\next| again to define the things that are
%    to be done.
%    Remember that the name of the current environment is
%    held in |\@currenvir|, the characters accumulated
%    by |\verbatim@testend| are in |\@tempc|.
%    So we simply compare these and prepare to execute
%    |\end{|\meta{current environment}|}|
%    macro if they match.
%    Before we do this we call |\verbatim@finish| to process
%    the last line.
%    We define |\next| via |\edef| so that
%    |\@currenvir| is replaced by its expansion.
%    Therefore we need |\noexpand| to inhibit the expansion
%    of |\end| at this point.
%    \begin{macrocode}
       \ifx\@tempc\@currenvir
         \verbatim@finish
         \edef\next{\noexpand\end{\@currenvir}%
%    \end{macrocode}
%    Without this trick the |\end| command would not be able
%    to correctly check whether its argument matches the name of
%    the current environment and you'd get an
%    interesting \LaTeX{} error message such as:
%    \begin{verbatim}
%! \begin{verbatim*} ended by \end{verbatim*}.
%\end{verbatim}
%    But what do we do with the rest of the characters, those
%    that remain on that line?
%    We call |\verbatim@rescan| to take care of that.
%    Its first argument is the name of the environment just
%    ended, in case we need it again.
%    |\verbatim@rescan| takes the list of characters to be
%    reprocessed as its second argument.
%    (This token list was inserted after the current macro
%    by |\verbatim@@@|.)
%    Since we are still in an |\edef| we protect it
%    by means of|\noexpand|.
%    \begin{macrocode}
                    \noexpand\verbatim@rescan{\@currenvir}}%
%    \end{macrocode}
%    If the names do not match, we reinsert everything read up
%    to now and prepare to call |\verbatim@| to process
%    the rest of the line.
%    \begin{macrocode}
       \else
         \expandafter\verbatim@addtoline
           \expandafter{\the\@temptokena[}%
           \expandafter\verbatim@addtoline
             \expandafter{\@tempc]}%
         \let\next\verbatim@
       \fi
%    \end{macrocode}
%    Finally we call |\next|.
%    \begin{macrocode}
       \next}%
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\verbatim@rescan}
%    In principle |\verbatim@rescan| could be used to
%    analyse the characters remaining after the |\end{...}|
%    command and pretend that these were read
%    ``properly'', assuming ``standard'' category codes are in
%    force.\footnote{Remember that they were all read with
%          category codes $11$ (letter) and $12$ (other) so
%          that control sequences are not recognized as such.}
%    But this is not always possible (when there are unmatched
%    curly braces in the rest of the line).
%    Besides, we think that this is not worth the effort:
%    After a {\tt verbatim} or {\tt verbatim*} environment
%    a new line in the output is begun anyway,
%    and an |\end{comment}| can easily be put on a line by itself.
%    So there is no reason why there should be any text here.
%    For the benefit of the user who did put something there
%    (a comment, perhaps)
%    we simply issue a warning and drop them.
%    The method of testing is explained in Appendix~D, p.\ 376 of
%    the \TeX{}book. We use |^^M| instead of the |!|
%    character used there
%    since this is a character that cannot appear in |#1|.
%    The two |\noexpand| primitives are necessary to avoid
%    expansion of active characters and macros.
%
%    One extra subtlety should be noted here: remember that
%    the token list we are currently building will first be
%    processed by the |\lowercase| primitive before \TeX{}
%    carries out the definitions.
%    This means that the `|C|' character in the
%    argument to the |\@warning| macro must be protected against
%    being changed to `|c|'.  That's the reason why we added the
%    |\lccode`\C=`\C| assignment above.
%    We can now finish the argument to |\lowercase| as well as the
%    group in which the category codes were changed.
%    \begin{macrocode}
  \gdef\verbatim@rescan#1#2~{\if\noexpand~\noexpand#2~\else
        \@warning{Characters dropped after `\string\end{#1}'}\fi}}
\endgroup
%    \end{macrocode}
% \end{macro}
%
%
% \subsection{The {\tt\bslash verbatiminput} command}
%
% \begin{macro}{\verbatiminput}
%    |\verbatiminput| first starts a group
%    to keep font and category changes local.
%    \begin{macrocode}
\def\verbatiminput{\begingroup
%    \end{macrocode}
%    The right sequence of actions is crucial here.
%    First we must check if a star follows.
%    Then we must read the argument (the file name).
%    Finally we must set up everything to read the contents of the
%    file verbatim.
%    Therefore we must not start by calling |\@verbatim| to change
%    font and the category code of characters.
%    Instead we call one of the macros |\sverbatim@input| or
%    |\verbatim@input|, depending on whether a star follows.
%    \begin{macrocode}
  \@ifstar\sverbatim@input\verbatim@input}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\sverbatim@input}
%    |\sverbatim@input| reads the file name argument and sets up
%    everything as in the |\verbatim| macro.
%    Then it reads in the file, finishes off the {\tt trivlist}
%    environment started by |\@verbatim| and closes the group
%    opened in |\verbatiminput|.
%    This restores everything to its normal settings.
% \changes{v1.2f}{90/01/31}{Added `@doendpe.  Found by Erica Harris.}
% \changes{v1.1c}{89/10/19}{Forgotten `endtrivlist added.
%                           Found by Chris Rowley.}
%    \begin{macrocode}
\def\sverbatim@input#1{\@verbatim
  \@input{#1}\endtrivlist\endgroup\@doendpe}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\verbatim@input}
%    |\verbatim@input| is nearly the same; it additionally calls
%    |\frenchspacing| and |\@vobeyspaces| (as in
%    |\verbatim| and |\verb|).
% \changes{v1.2f}{90/01/31}{Added `@doendpe.  Found by Erica Harris.}
% \changes{v1.1c}{89/10/19}{Forgotten `endtrivlist added.
%                           Found by Chris Rowley.}
%    \begin{macrocode}
\def\verbatim@input#1{\@verbatim
  \frenchspacing \@vobeyspaces
  \@input{#1}\endtrivlist\endgroup\@doendpe}
%    \end{macrocode}
% \end{macro}
%
%
% \subsection{Redefinition of the {\tt \bslash verb} command.}
%
% The implementation here has the following advantage over that in
% the original \LaTeX: it will not accept the end of the input
% line being reached before the verbatim text has ended.  Instead, it
% will end the verbatim text and generate an error message.
%
% \begin{macro}{\verb}
% \changes{v1.1a}{89/10/16}{`verb added.}
%    We need special category codes during the definition:
%    the end of line character (|^^M|) must be an active
%    character.  We do this in the same way as above:
% \changes{v1.4g}{91/11/21}{Changed `verb so that it works in math mode as well.
%          Suggested by Chris Rowley and Bernd Raichle.}
%    \begin{macrocode}
\begingroup
  \catcode`\~=\active
  \lccode`\~=`\^^M
%    \end{macrocode}
%    We use the following trick proposed by Bernd Raichle:
%    The very first token in the list given to |\lowercase| is
%    the |\endgroup| primitive. This means that it is processed by
%    \TeX{} immediately after |\lowercase| is finished, thus ending
%    the group started by |\begingroup| above.
%    \begin{macrocode}
  \lowercase{\endgroup
%    \end{macrocode}
%    The first thing we do in |\verb| is to check for math mode.
%    If this is the case the |\bgroup| is used as open brace for the
%    |\hbox|. Otherwise, we force horizontal mode and include an
%    empty |\hbox| (|\null|). This is necessary in case the first
%    character to be processed verbatim happens to be a space and
%    if a line break occurs at this point. If we did not include
%    the empty |\hbox| this space would disappear.
%    \begin{macrocode}
    \gdef\verb{\relax
      \ifmmode \hbox \else \leavevmode\null \fi
      \bgroup
%    \end{macrocode}
%    We use here
%    |\verbatim@font| rather than switching directly to
%    |\tt|.
%    \begin{macrocode}
      \verbatim@font
%    \end{macrocode}
%    Now we make the end of line character active and define it to
%    restore everything back to normal and to signal an error.
%    Remember that every occurence of the |~| character is changed
%    into the end of line character.
% \changes{v1.4g}{91/11/21}{Changed control-m to tilde in category
%                   code assignment, as it is converted to control-m
%                   by the `lowercase primitive. This improves the
%                   readability. Suggested by Bernd Raichle.}
% \changes{v1.4b}{90/07/14}{Added `catcode assignment that had
%                   disappeared somehow.}
%    \begin{macrocode}
      \catcode`~\active
      \def~{\egroup\@latexerr{\string\verb\space command ended by
                              end of line.}\@ehc}%
%    \end{macrocode}
%    The rest is copied from {\tt latex.tex} where we have replaced
%    one macro (|\@verb|) by its expansion.
% \changes{v1.3a}{90/02/04}{Removed unnecessary braces.}
% \changes{v1.4}{90/03/07}{Replaced `@verb by its expansion.}
%    \begin{macrocode}
    \let\do\@makeother \dospecials
    \@ifstar\@sverb{\@vobeyspaces \frenchspacing \@sverb}}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@sverb}
% \changes{v1.4h}{91/12/18}{Changed `@sverb so that `verb would work
%           in a tabular or array environment.}
% \changes{v1.4i}{92/01/20}{Errors corrected.}
%    |\@sverb| gains control when we are ready to look for the
%    delimiting character.  It reads it and defines this character
%    to be equivalent to |\egroup|, i.e., to a closing brace.
%    That means it will restore everything to normal when it occurs for
%    the second time.
%    \begin{macrocode}
\def\@sverb#1{%
  \catcode`#1\active
  \lccode`\~`#1%
  \lowercase{\let~\egroup}}%
%    \end{macrocode}
% \end{macro}
%
% \Finale
%
\endinput