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letter.dtx
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% \iffalse meta-comment
%
% Copyright (C) 1993-2025
% The LaTeX Project and any individual authors listed elsewhere
% in this file.
%
% This file is part of the LaTeX base system.
% -------------------------------------------
%
% It may be distributed and/or modified under the
% conditions of the LaTeX Project Public License, either version 1.3c
% of this license or (at your option) any later version.
% The latest version of this license is in
% https://www.latex-project.org/lppl.txt
% and version 1.3c or later is part of all distributions of LaTeX
% version 2008 or later.
%
% This file has the LPPL maintenance status "maintained".
%
% The list of all files belonging to the LaTeX base distribution is
% given in the file `manifest.txt'. See also `legal.txt' for additional
% information.
%
% The list of derived (unpacked) files belonging to the distribution
% and covered by LPPL is defined by the unpacking scripts (with
% extension .ins) which are part of the distribution.
%
% \fi
%
%
% \iffalse
% \section{Identification}
%
%
% This document class can only be used with \LaTeXe, so we make
% sure that an appropriate message is displayed when another \TeX{}
% format is used.
% \begin{macrocode}
%<+letter>\NeedsTeXFormat{LaTeX2e}[1996/06/01]
% \end{macrocode}
%
% Announce the Class name and its version.
% \begin{macrocode}
%<+letter>\ProvidesClass{letter}
%<*driver>
\ProvidesFile{letter.drv}
%</driver>
[2024/08/12 v1.3c
%<+letter> Standard LaTeX document class]
% \end{macrocode}
%
% \section{The documentation driver file}
%
% We have our own document class to format the \LaTeXe{}
% documentation.
% \fi
% \changes{v1.0}{1993/12/07}{Use class ltxdoc document class}
% \iffalse
% \begin{macrocode}
%<*driver>
]
\documentclass{ltxdoc}
% \end{macrocode}
%
% We don't want everything to appear in the index.
% \begin{macrocode}
\DoNotIndex{\@Alph,\@alph,\@arabic,\@badmath}
\DoNotIndex{\@centercr}
\DoNotIndex{\@empty,\@ignoretrue}
\DoNotIndex{\@ixpt}
\DoNotIndex{\@M,\@minus,\@ne,\@plus}
\DoNotIndex{\\,\addtolength}
\DoNotIndex{\advance}
\DoNotIndex{\ast,\begin,\begingroup,\bfseries,\bgroup,\box}
\DoNotIndex{\bullet}
\DoNotIndex{\cdot,\cr,\day,\DeclareOption}
\DoNotIndex{\def,\DocInput,\documentclass}
\DoNotIndex{\DoNotIndex,\egroup,\ifx,\else,\fi,\endtrivlist}
\DoNotIndex{\EnableCrossrefs,\end,\end@dblfloat,\end@float,\endgroup}
\DoNotIndex{\endlist,\everycr,\ExecuteOptions}
\DoNotIndex{\filedate,\filename,\fileversion}
\DoNotIndex{\global,\halign,\hangindent,\hbox,\hfil,\hfill,\hrule}
\DoNotIndex{\hsize,\hskip,\hspace,\hss,\ifcase,\or,\fi}
\DoNotIndex{\ifvmode,\fi,\ifnum,\fi,\input}
\DoNotIndex{\kern,\leavevmode,\let,\leftmark}
\DoNotIndex{\list,\llap,\long,\m@ne,\m@th,\mark}
\DoNotIndex{\month,\newcommand,\newcounter,\newenvironment}
\DoNotIndex{\NeedsTeXFormat,\newdimen}
\DoNotIndex{\newpage,\nobreak,\noindent,\number}
\DoNotIndex{\p@}
\DoNotIndex{\pagestyle,\par}
\DoNotIndex{\penalty,\PrintChanges,\PrintIndex,\ProcessOptions}
\DoNotIndex{\protect,\ProvidesClass,\raggedbottom,\raggedright}
\DoNotIndex{\refstepcounter,\relax,\renewcommand,\reset@font}
\DoNotIndex{\rightmargin,\rlap,\rmfamily}
\DoNotIndex{\setbox,\setcounter,\setlength}
\DoNotIndex{\skip,\slshape,\space}
\DoNotIndex{\trivlist,\typeout,\tw@}
\DoNotIndex{\vskip,\vspace,\year,\z@}
%
\CodelineNumbered
\CodelineIndex
\EnableCrossrefs
\RecordChanges
% \end{macrocode}
% We use so many \file{docstrip} modules that we set the
% \texttt{StandardModuleDepth} counter to 1.
% \begin{macrocode}
\setcounter{StandardModuleDepth}{1}
% \end{macrocode}
% The following command retrieves the date and version information
% from the file.
% \begin{macrocode}
\GetFileInfo{letter.drv}
% \end{macrocode}
% Some commonly used abbreviations
% \begin{macrocode}
\newcommand*\Lopt[1]{\textsf {#1}}
\newcommand*\file[1]{\texttt {#1}}
\newcommand*\Lcount[1]{\textsl {\small#1}}
\newcommand*\pstyle[1]{\textsl {#1}}
% \end{macrocode}
% We also want the full details.
% \begin{macrocode}
\begin{document}
\DocInput{letter.dtx}
\PrintIndex
% ^^A\PrintChanges
\end{document}
%</driver>
% \end{macrocode}
% \fi
%
% \changes{v1.1}{1993/12/18}{Changes to make it work with
% compatibility mode.}
% \changes{v1.1a}{1993/12/19}{Removed float parms}
%
% \changes{v1.1c}{1994/01/17}{Moved definition of \cs{@textop} to
% initialization section, to counteract setting of \cs{@texttop} in
% \cs{raggedbottom}.}
%
% \changes{v1.1d}{1994/01/20}{Corrected margins: Now computed from
% \cs{paperwidth} and \cs{textwidth}, so that the text is
% horizontally centered.}
% \changes{v1.1e}{1994/02/03}{Corrected checksum}
%
% \changes{v1.2a}{1994/02/12}{Removed onecolumn and twocolumn options.}
% \changes{v1.2a}{1994/02/12}{Changed label producing commands in .aux
% file.}
%
% \changes{v1.2b}{1994/02/28}{Moved driver further up.}
%
% \changes{v1.2c}{1994/03/08}{Always write .aux file.}
% \changes{v1.2f}{1994/04/29}{Use LaTeX instead of LaTeX2e in messages}
% \changes{v1.2f}{1994/04/29}{Removed \cs{typeout} message}
% \changes{v1.2g}{1994/05/01}{Removed the use of \cs{fileversion}
% c.s.}
% \changes{v1.2j}{1994/06/01}{Corrected driver code.}
% \changes{v1.2k}{1994/06/17}{Various documentation enhancements}
% \changes{v1.2p}{1994/12/11}{Use \cs{newcommand*} to define
% user-level commands that take an argument}
% \changes{v1.2q}{1995/05/17}{cleaned up \cs{changes entries}}
% \changes{v1.2q}{1995/05/18}{replaced \cs{hbox to} by \cs{hb@xt@}}
% \changes{v1.2r}{1995/05/23}{removed a superfluous brace}
% \changes{v1.3a}{2020/03/07}{merged changes to classes.dtx into letter.dtx}
%
% \iffalse
% Copyright (C) 1994 LaTeX Project, Frank Mittelbach
% and Rainer Sch\"opf, all rights reserved.
% \fi
%
% \author{Leslie Lamport and Frank Mittelbach and Rainer Sch\"opf}
%
% \title{Standard Letter Document Class for \LaTeX{} version 2e}
%
%
% \MaintainedByLaTeXTeam{latex}
% \maketitle
% \tableofcontents
%
% \MaybeStop{}
%
%
% \section{Initial Code}
%
% In this part we define a few commands that are used later on.
%
% \begin{macro}{\@ptsize}
% This control sequence is used to store the second digit of the
% pointsize we are typesetting in. So, normally, it's value is one
% of 0, 1 or 2.
% \begin{macrocode}
%<*letter>
\newcommand\@ptsize{}
% \end{macrocode}
% \end{macro}
%
%
%
% \subsection{Setting Paper Sizes}
%
% The variables |\paperwidth| and |\paperheight| should reflect the
% physical paper size after trimming. For desk printer output this
% is usually the real paper size since there is no post-processing.
% \changes{v1.0a}{1993/12/14}{Corrected typo, A4 is not 279 mm high}
% \begin{macrocode}
\DeclareOption{a4paper}
{\setlength\paperheight {297mm}%
\setlength\paperwidth {210mm}}
\DeclareOption{a5paper}
{\setlength\paperheight {210mm}%
\setlength\paperwidth {148mm}}
\DeclareOption{b5paper}
{\setlength\paperheight {250mm}%
\setlength\paperwidth {176mm}}
\DeclareOption{letterpaper}
{\setlength\paperheight {11in}%
\setlength\paperwidth {8.5in}}
\DeclareOption{legalpaper}
{\setlength\paperheight {14in}%
\setlength\paperwidth {8.5in}}
\DeclareOption{executivepaper}
{\setlength\paperheight {10.5in}%
\setlength\paperwidth {7.25in}}
% \end{macrocode}
%
% \changes{v1.2o}{1994/08/26}{Added the option \textsf{landscape}}
% The option \Lopt{landscape} switches the values of |\paperheight|
% and |\paperwidth|, assuming the dimensions were given for portrait
% paper.
% \begin{macrocode}
\DeclareOption{landscape}
{\setlength\@tempdima {\paperheight}%
\setlength\paperheight {\paperwidth}%
\setlength\paperwidth {\@tempdima}}
% \end{macrocode}
%
% \subsection{Choosing the type size}
%
% The type size options are handled by defining |\@ptsize| to
% contain the last digit of the size in question and branching on
% |\ifcase| statements. This is done for historical reasons to stay
% compatible with other packages that use the |\@ptsize| variable
% to select special actions. It makes the declarations of size
% options less than 10pt difficult, although one can probably use
% \texttt{9} and \texttt{8} assuming that a class won't define both
% \Lopt{8pt} and \Lopt{18pt} options.
%
% \begin{macrocode}
\DeclareOption{10pt}{\renewcommand\@ptsize{0}}
\DeclareOption{11pt}{\renewcommand\@ptsize{1}}
\DeclareOption{12pt}{\renewcommand\@ptsize{2}}
% \end{macrocode}
%
%
% \subsection{Two-side or one-side printing}
%
% Two-sided printing was not supported in the \LaTeX~2.09 version
% of this document class.
% \changes{v1.2e}{1994/04/28}{Added oneside option and twoside option
% in native mode}
% \begin{macrocode}
\if@compatibility
\DeclareOption{twoside}{\@latexerr{No `twoside' layout for letters}%
\@eha}
\else
\DeclareOption{twoside}{\@twosidetrue \@mparswitchtrue}
\fi
% \end{macrocode}
%
%
% \begin{macrocode}
\DeclareOption{oneside}{\@twosidefalse \@mparswitchfalse}
% \end{macrocode}
%
% \subsection{Draft option}
%
% If the user requests \Lopt{draft} we show any overfull boxes.
% We could probably add some more interesting stuff to this option.
% \begin{macrocode}
\DeclareOption{draft}{\setlength\overfullrule{5pt}}
\DeclareOption{final}{\setlength\overfullrule{0pt}}
% \end{macrocode}
%
%
% \subsection{Equation numbering on the left}
%
% The option \Lopt{leqno} can be used to get the equation numbers
% on the left side of the equation.
% \changes{v1.1c}{1994/01/17}{Option leqno now read from
% \file{leqno.clo}.}
% \begin{macrocode}
\DeclareOption{leqno}{\input{leqno.clo}}
% \end{macrocode}
%
% \subsection{Flush left displays}
%
% The option \Lopt{fleqn} redefines the displayed math environments
% in such a way that they come out flush left, with an indentation
% of |\mathindent| from the prevailing left margin.
% \changes{v1.1}{1993/12/18}{Corrected typo in \cs{renewcommand},
% doubled hash marks.}
% \changes{v1.1c}{1994/01/17}{Option fleqn now read from
% \file{fleqn.clo}.}
% \begin{macrocode}
\DeclareOption{fleqn}{\input{fleqn.clo}}
% \end{macrocode}
%
%
% \section{Executing Options}
%
% Here we execute the default options to initialize certain
% variables.
% \changes{v1.2e}{1994/04/28}{Added execution of `oneside' option}
% \begin{macrocode}
\ExecuteOptions{letterpaper,10pt,oneside,onecolumn,final}
% \end{macrocode}
%
% The |\ProcessOptions| command causes the execution of the code
% for every option \Lopt{foo} which is declared and for which the
% user typed the \Lopt{foo} option in his |\documentclass| command.
% For every option \Lopt{bar} he typed, which is not declared, the
% option is assumed to be a global option. All options will be
% passed as document options to any |\usepackage| command in the
% document preamble.
% \begin{macrocode}
\ProcessOptions
% \end{macrocode}
% Now that all the options have been executed we can load the
% chosen class option file that contains all size dependent code.
% \begin{macrocode}
\input{size1\@ptsize.clo}
% \end{macrocode}
%
%
% \section{Loading Packages}
%
% The standard class files do not load additional packages.
%
%
% \section{Document Layout}
% \label{sec:maincode}
%
% In this section we are finally dealing with the nasty typographical
% details.
%
% \subsection{Paragraphing}
%
% \begin{macro}{\lineskip}
% \begin{macro}{\normallineskip}
% These parameters control \TeX's behavior when two lines tend to
% come too close together.
% \begin{macrocode}
\setlength\lineskip{1\p@}
\setlength\normallineskip{1\p@}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\baselinestretch}
% This is used as a multiplier for |\baselineskip|. The default is
% to {\em not\/} stretch the baselines.
% \begin{macrocode}
\renewcommand\baselinestretch{}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\parskip}
% \begin{macro}{\parindent}
% |\parskip| gives extra vertical space between paragraphs and
% |\parindent| is the width of the paragraph indentation.
% Letters are typeset without paragraph indentation.
% \begin{macrocode}
\setlength\parskip{0.7em}
\setlength\parindent{0\p@}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\@lowpenalty}
% \begin{macro}{\@medpenalty}
% \begin{macro}{\@highpenalty}
% The commands |\nopagebreak| and |\nolinebreak| put in penalties
% to discourage these breaks at the point they are put in.
% They use |\@lowpenalty|, |\@medpenalty| or |\@highpenalty|,
% dependent on their argument.
% \begin{macrocode}
\@lowpenalty 51
\@medpenalty 151
\@highpenalty 301
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\clubpenalty}
% \begin{macro}{\widowpenalty}
% These penalties are used to discourage club and widow lines.
% Because we use their default values we only show them here,
% commented out.
% \begin{macrocode}
% \clubpenalty 150
% \widowpenalty 150
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\displaywidowpenalty}
% \begin{macro}{\predisplaypenalty}
% \begin{macro}{\postdisplaypenalty}
% Discourage (but not so much) widows in front of a math display
% and forbid breaking directly in front of a display. Allow break
% after a display without a penalty. Again the default values are
% used, therefore we only show them here.
% \begin{macrocode}
% \displaywidowpenalty 50
% \predisplaypenalty 10000
% \postdisplaypenalty 0
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\interlinepenalty}
% Allow the breaking of a page in the middle of a paragraph.
% \begin{macrocode}
% \interlinepenalty 0
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\brokenpenalty}
% We allow the breaking of a page after a hyphenated line.
% \begin{macrocode}
% \brokenpenalty 0
% \end{macrocode}
% \end{macro}
%
%
% \subsection{Page Layout}
%
% All margin dimensions are measured from a point one inch from the
% top and lefthand side of the page.
%
% \subsubsection{Vertical spacing}
%
% \begin{macro}{\headheight}
% \begin{macro}{\headsep}
% The |\headheight| is the height of the box that will contain the
% running head. The |\headsep| is the distance between the bottom
% of the running head and the top of the text. |\topskip| is the
% |\baselineskip| for the first line on a page, its value depends
% on the size option that was specified. Therefore it is
% initialized in one of the \file{size1x.clo} files.
% \begin{macrocode}
\setlength\headheight{12\p@}
\setlength\headsep {45\p@}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\footskip}
% The distance from the baseline of the box which contains the
% running footer to the baseline of last line of text is controlled
% by the |\footskip|.
% Bottom of page:
% \begin{macrocode}
\setlength\footskip{25\p@}
% \end{macrocode}
% \end{macro}
%
% \changes{v1.2n}{1994/07/13}{Setting of \cs{maxdepth} and
% \cs{@maxdepth} already happens in the size.. files, removed
% here}
%
% \subsubsection{The dimension of text}
%
% \begin{macro}{\textwidth}
% When we are in compatibility mode we have to make sure that the
% dimensions of the printed area are not different from what the
% user was used to see.
%
% \changes{v1.2n}{1994/07/13}{Setting \cs{textwidth} to a fixed value
% should only happen in compatibility mode}
% \begin{macrocode}
\if@compatibility
\setlength\textwidth{365\p@}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\textheight}
% Now that we have computed the width of the text, we have to take
% care of the height. The |\textheight| is the height of text
% (including footnotes and figures, excluding running head and
% foot).
% \changes{v1.2n}{1994/07/13}{Setting \cs{textheight} to a fixed value
% should only happen in compatibility mode}
% \begin{macrocode}
\setlength\textheight{505\p@}
\fi
% \end{macrocode}
% In native mode we use the dimensions as they were computed by one
% of the \Lopt{xxpt} options, together with one of the
% \Lopt{..paper} options.
% \end{macro}
%
% \subsubsection{Margins}
%
% \begin{macro}{\oddsidemargin}
% \begin{macro}{\evensidemargin}
% \begin{macro}{\marginparwidth}
% \changes{v1.1d}{1994/01/20}{Corrected margins: Now computed from
% \cs{paperwidth} and \cs{textwidth}.} The values of
% |\oddsidemargin| and |\evensidemargin| are computed from those of
% |\paperwidth| and |\textwidth|.
% \changes{v1.2n}{1994/07/13}{Added fixed values for these parameters
% in compatibility mode}
% \begin{macrocode}
\if@compatibility
\setlength\oddsidemargin{53pt}
\setlength\evensidemargin{53pt}
\setlength\marginparwidth{90pt}
\else
\setlength\@tempdima{\paperwidth}
\addtolength\@tempdima{-2in}
\addtolength\@tempdima{-\textwidth}
\setlength\oddsidemargin {.5\@tempdima}
\setlength\evensidemargin {\oddsidemargin}
\setlength\marginparwidth {90\p@}
\fi
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\marginparsep}
% \begin{macro}{\marginparpush}
% The horizontal space between the main text and marginal notes is
% determined by |\marginparsep|, the minimum vertical separation
% between two marginal notes is controlled by |\marginparpush|.
% \begin{macrocode}
\setlength\marginparsep {11\p@}
\setlength\marginparpush{5\p@}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\topmargin}
% The |\topmargin| is the distance between the top of `the
% printable area' --which is 1 inch below the top of the paper--
% and the top of the box which contains the running head.
%
% It can now be computed from the values set above.
% \begin{macrocode}
\setlength\topmargin{27pt}
% \end{macrocode}
% \end{macro}
%
%
% \subsubsection{Footnotes}
%
% \begin{macro}{\footnotesep}
% |\footnotesep| is the height of the strut placed at the beginning
% of every footnote. It equals the height of a normal
% |\footnotesize| strut in this
% class, thus no extra space occurs between footnotes.
% \begin{macrocode}
\setlength\footnotesep{12\p@}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\footins}
% |\skip\footins| is the space between the last line of the main
% text and the top of the first footnote.
% \begin{macrocode}
\setlength{\skip\footins}{10\p@ \@plus 2\p@ \@minus 4\p@}
% \end{macrocode}
% \end{macro}
%
%
% \subsection{Page Styles}
%
% The page style \pstyle{foo} is defined by defining the command
% |\ps@foo|. This command should make only local definitions.
% There should be no stray spaces in the definition, since they
% could lead to mysterious extra spaces in the output (well, that's
% something that should be always avoided).
%
% \begin{macro}{\@evenhead}
% \begin{macro}{\@oddhead}
% \begin{macro}{\@evenfoot}
% \begin{macro}{\@oddfoot}
% The |\ps@...| command defines the macros |\@oddhead|,
% |\@oddfoot|, |\@evenhead|, and |\@evenfoot| to define the running
% heads and feet---e.g., |\@oddhead| is the macro to produce the
% contents of the heading box for odd-numbered pages. It is called
% inside an |\hbox| of width |\textwidth|.
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsubsection{Marking conventions}
%
% To make headings determined by the sectioning commands, the page
% style defines the commands |\chaptermark|, |\sectionmark|,
% \ldots, where |\chaptermark{|\meta{text}|}| is called by
% |\chapter| to set a mark, and so on.
%
% The |\...mark| commands and the |\...head| macros are defined
% with the help of the following macros. (All the |\...mark|
% commands should be initialized to no-ops.)
%
% \LaTeX{} extends \TeX's |\mark| facility by producing two kinds
% of marks, a `left' and a `right' mark, using the following
% commands:
% \begin{flushleft}
% |\markboth{|\meta{left}|}{|\meta{right}|}|: Adds both marks.
%
% |\markright{|\meta{right}|}|: Adds a `right' mark.
%
% |\leftmark|: Used in the |\@oddhead|, |\@oddfoot|, |\@evenhead|
% or |\@evenfoot| macros, it gets the current `left'
% mark. |\leftmark| works like \TeX's |\botmark|
% command.
%
% |\rightmark|: Used in the |\@oddhead|, |\@oddfoot|, |\@evenhead|
% or |\@evenfoot| macros, it gets the current
% `right' mark. |\rightmark| works like \TeX's
% |\firstmark| command.
% \end{flushleft}
%
% The marking commands work reasonably well for right marks
% `numbered within' left marks--e.g., the left mark is changed by a
% |\chapter| command and the right mark is changed by a |\section|
% command. However, it does produce somewhat anomalous results if
% two |\markboth|'s occur on the same page.
%
%
% Commands like |\tableofcontents| that should set the marks in some
% page styles use a |\@mkboth| command, which is |\let| by the
% pagestyle command (|\ps@...|) to |\markboth| for setting the
% heading or to |\@gobbletwo| to do nothing.
%
%
% \subsubsection{Defining the page styles}
% \label{sec:pagestyle}
%
% The pagestyles \pstyle{empty} and \pstyle{plain} are defined in
% the \LaTeX{} kernel (\file{ltpage.dtx}), but these definitions
% are changed to a simpler version for this document class.
%
% \begin{macro}{\ps@headings}
% The definition of the page style \pstyle{headings} has to be
% different for two sided printing than it is for one sided
% printing.
%
% \changes{v1.2e}{1994/04/28}{Added twoside support}
% \begin{macrocode}
\if@twoside
\def\ps@headings{%
% \end{macrocode}
% The running feet are empty in this page style.
% \begin{macrocode}
\let\@oddfoot\@empty\let\@evenfoot\@empty
% \end{macrocode}
% The running head contains some information about this letter. The
% head is the same for even and odd pages.
% \changes{v1.2i}{1994/05/12}{Made running heads the same on odd and
% even pages}
% \changes{v1.2k}{1994/06/17}{Added a missing brace}
% \begin{macrocode}
\def\@oddhead{\slshape\headtoname{} \ignorespaces\toname
\hfil \@date
\hfil \pagename{} \thepage}%
\let\@evenhead\@oddhead}
% \end{macrocode}
% For one sided printing we don't need to define |\@evenhead| so
% the definition is somewhat simpler.
% \begin{macrocode}
\else
\def\ps@headings{%
\let\@oddfoot\@empty
\def\@oddhead{\slshape\headtoname{} \ignorespaces\toname
\hfil \@date
\hfil \pagename{} \thepage}}
\fi
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\ps@empty}
% The definition of the page style \pstyle{empty} is simple:
% No running head or foot at all.
% \changes{v1.2e}{1994/04/28}{Also make even feet and head empty}
% \begin{macrocode}
\def\ps@empty{%
\let\@oddfoot\@empty\let\@oddhead\@empty
\let\@evenfoot\@empty\let\@evenhead\@empty}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ps@firstpage}
% The page style \pstyle{firstpage} puts the telephone number
% in the proper place for the letterhead. It should be adapted
% to site conventions. The size of the number is determined
% depending on the main size.
% \begin{macrocode}
\def\ps@firstpage{%
\let\@oddhead\@empty
\def\@oddfoot{\raisebox{-45\p@}[\z@]{%
\hb@xt@\textwidth{\hspace*{100\p@}%
\ifcase \@ptsize\relax
\normalsize
\or
\small
\or
\footnotesize
\fi
\fromlocation \hfill \telephonenum}}\hss}}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ps@plain}
% The definition of the page style \pstyle{plain} is again simple.
% \changes{v1.2e}{1994/04/28}{Added definition of \cs{@evenfoot}
% because of twoside option}
% \changes{v1.2s}{1995/05/25}{replace \cs{rmfamily} with
% \cs{normalfont} (PR 1578)}
% \begin{macrocode}
\def\ps@plain{%
\let\@oddhead\@empty
\def\@oddfoot{\normalfont\hfil\thepage\hfil}%
\def\@evenfoot{\normalfont\hfil\thepage\hfil}}
% \end{macrocode}
% \end{macro}
%
%
%
% \section{Document Markup}
%
% \subsection{Global Declarations}
%
% \begin{macro}{\name}
% \begin{macro}{\signature}
% \begin{macro}{\address}
% \begin{macro}{\location}
% \begin{macro}{\telephone}
% The following declarations, shown with examples, give information
% about the sender:
% \begin{itemize}
% \item |\name{Dr. L. User}| : to be used for the return address on
% the envelope.
% \begin{macrocode}
\newcommand*\name[1]{\def\fromname{#1}}
% \end{macrocode}
% \item |\signature{Larry User}| : goes after the closing.
% \begin{macrocode}
\newcommand*\signature[1]{\def\fromsig{#1}}
% \end{macrocode}
% \item |\address{3245 Foo St.\\Gnu York}| : used as the return
% address in the
% letter and on the envelope. If not declared, then an
% institutional standard address is used.
% \begin{macrocode}
\newcommand*\address[1]{\def\fromaddress{#1}}
% \end{macrocode}
% \item |\location{Room 374}| : Acts as modifier to the standard
% institutional address.
% \begin{macrocode}
\newcommand*\location[1]{\def\fromlocation{#1}}
% \end{macrocode}
% \item |\telephone{(415)123-4567}| : Just in case some style puts it
% on the letter.
% \changes{v1.2m}{1994/06/23}{Removed typo (\#[] instead of [1])}
% \begin{macrocode}
\newcommand*\telephone[1]{\def\telephonenum{#1}}
% \end{macrocode}
% \end{itemize}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\fromname}
% \begin{macro}{\fromsig}
% \begin{macro}{\fromaddress}
% \begin{macro}{\fromlocation}
% \begin{macro}{\telephonenum}
% We make sure that the internal control sequences that are used to
% store the information exist and are empty.
% \begin{macrocode}
\name{}
\signature{}
\address{}
\location{}
\telephone{}
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\makelabels}
% The |\makelabels| declaration causes mailing labels to be made.
% \begin{macrocode}
\newcommand*\makelabels{%
% \end{macrocode}
% At the beginning of the document, we need to activate the
% |\@mlabel| and |\@startlabels| commands, as well as write
% |\@startlabels| to the |.aux| file.
% \begin{macrocode}
\AtBeginDocument{%
\let\@startlabels\startlabels
\let\@mlabel\mlabel
\if@filesw
\immediate\write\@mainaux{\string\@startlabels}\fi}%
% \end{macrocode}
% At the end of the document we need to write |\clearpage| to the
% |.aux| file.
% \begin{macrocode}
\AtEndDocument{%
\if@filesw\immediate\write\@mainaux{\string\clearpage}\fi}}
% \end{macrocode}
% |\makelabels| is allowed only before the |\begin{document}|
% command.
% \begin{macrocode}
\@onlypreamble\makelabels
% \end{macrocode}
% \end{macro}
%
% \subsection{The generic letter commands}
%
% \begin{environment}{letter}
% The letter environment creates a new letter, starting from page
% $1$, with footnotes starting from $1$ as well.
% (The first page is unnumbered.) It has a single argument, which
% is the addressee and his address, as in
% \changes{v1.3c}{2024/08/12}{Alter sample address (gh/1439)}
%\begin{verbatim}
% \begin{letter}{Sam Jones \\
% Institute for Trivial Study\\
% Princeton, N.J.}
%\end{verbatim}
% Local declarations, such as |\address|, can follow the
% |\begin{letter}|.
% \changes{v1.2e}{1994/04/28}{When printing twosided a new letter
% shouldn't start on the back of the previous one. Added insertion
% of a blank page when necessary.}
% \changes{v1.2z}{1999/04/29}{Reset footnote counter to 0, (PR 2957).}
% \begin{macrocode}
\newenvironment{letter}[1]
{\newpage
\if@twoside \ifodd\c@page
\else\thispagestyle{empty}\null\newpage\fi
\fi
\c@page \@ne
\c@footnote \z@
\interlinepenalty=200 % smaller than the TeXbook value
% \end{macrocode}
% The |\leavevmode| and |\ignorespaces| commands are there for
% protecting against an empty argument.
% \begin{macrocode}
\@processto{\leavevmode\ignorespaces #1}}
% \end{macrocode}
% The end of the environment possibly writes the address
% information on the \file{.aux} file.
% \changes{v1.2p}{1994/12/11}{No longer redefine \cs{protect} but use
% one of the available settings}
% \begin{macrocode}
{\stopletter\@@par\pagebreak\@@par
\if@filesw
\begingroup
\let\\=\relax
\let\protect\@unexpandable@protect
\immediate\write\@auxout{%
\string\@mlabel{\returnaddress}{\toname\\\toaddress}}%
\endgroup
\fi}
% \end{macrocode}
% \end{environment}
%
%
% \begin{macro}{\@processto}
% \begin{macro}{\@xproc}
% \begin{macro}{\@yproc}
% |\@processto| gets the |\toname| and |\toaddress| from the letter
% environment's macro argument. |\@xproc| and |\@yproc| are auxiliary
% macros.
% \begin{macrocode}
\long\def\@processto#1{%
\@xproc #1\\@@@%
\ifx\toaddress\@empty
\else
\@yproc #1@@@%
\fi}
% \end{macrocode}
%
% \begin{macrocode}
\long\def\@xproc #1\\#2@@@{\def\toname{#1}\def\toaddress{#2}}
% \end{macrocode}
%
% \begin{macrocode}
\long\def\@yproc #1\\#2@@@{\def\toaddress{#2}}
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
%
% \subsubsection{Page breaking control}
%
% \begin{macro}{\stopbreaks}
% When the command |\stopbreaks| is issued no page breaks should
% occur until |\startbreaks| is called.
% \begin{macrocode}
\newcommand*\stopbreaks{%
\interlinepenalty\@M
\def\par{\@@par\nobreak}%
\let\\\@nobreakcr
\let\vspace\@nobreakvspace}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\nobreakvspace}
% \changes{v1.2t}{1996/01/20}{Made robust pr/2049}
% \begin{macro}{\@nobreakvspacex}
% \begin{macro}{\@nobreakcr}
% These are needed by |\stopbreaks|
% \begin{macrocode}
\DeclareRobustCommand\@nobreakvspace
{\@ifstar\@nobreakvspacex\@nobreakvspacex}
% \end{macrocode}
%
% \begin{macrocode}
\def\@nobreakvspacex#1{%
\ifvmode
\nobreak\vskip #1\relax
\else
\@bsphack\vadjust{\nobreak\vskip #1}\@esphack
\fi}
% \end{macrocode}
%
% \changes{v1.2w}{1997/01/07}
% {Simplify definition, for ltspace 1.2u. /2341}
% \begin{macrocode}
\def\@nobreakcr{\@ifstar{\@normalcr*}{\@normalcr*}}
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\startbreaks}
% This cancels the effect of |\stopbreaks|.
% \begin{macrocode}
\newcommand*\startbreaks{%
\let\\\@normalcr
\interlinepenalty 200%
\def\par{\@@par\penalty 200\relax}}
% \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\longindentation}
% The size of the indent to use before the closing of the letter.
% \begin{macrocode}
\newdimen\longindentation
\longindentation=.5\textwidth
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\indentedwidth}
% The width of the closing of the letter.
% \begin{macrocode}
\newdimen\indentedwidth
\indentedwidth=\textwidth
\advance\indentedwidth -\longindentation
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\opening}
% Text is begun with the |\opening| command, whose argument
% generates the salutation, as in
%\begin{verbatim}
% \opening{Dear Henry,}
%\end{verbatim}
% This should produce everything up to and including the
% `Dear Henry,' and a |\par| command that follows.
% Since there's a |\vfil| at the bottom of every page,
% it can add vertical fill to position a short letter.
% It should use the following commands:
% \begin{itemize}
% \item |\toname| : name part of `to' address.
% Will be one line long.
% \item |\toaddress| : address part of `to' address.
% The lines separated by |\\|.
% \item |\fromname| : name of sender.
% \item |\fromaddress| : argument of current |\address|