\def\fileversion{2.1}
\def\filedate{1994/02/10}
\def\docdate{1994/02/09}
% \CheckSum{271}
%\iffalse
%%% ====================================================================
%%%  @LaTeX-package-file{
%%%     author          = "Braams J.L.",
%%%     version         = "2.1",
%%%     date            = "10 February 1994",
%%%     time            = "01:27:31 MET",
%%%     filename        = "subeqnarray.dtx",
%%%     address         = "PTT Research
%%%                        St. Paulusstraat 4
%%%                        2264 XZ Leidschendam
%%%                        The Netherlands",
%%%     telephone       = "(70) 3325051",
%%%     FAX             = "(70) 3326477",
%%%     checksum        = "13995 400 1471 13429",
%%%     email           = "J.L.Braams@research.ptt.nl (Internet)",
%%%     codetable       = "ISO/ASCII",
%%%     keywords        = "",
%%%     supported       = "yes",
%%%     abstract        = "This package defines the subeqnarray
%%%                        and subeqnarray* environments, which behave
%%%                        like the eqnarray environment, except that
%%%                        the lines are numbered like 1a 1b 1c etc.
%%%                        To refer to these numbers an extra label
%%%                        command \slabel has been defined
%%%
%%%                        The equations and their numbers adhere to
%%%                        the standard LaTeX options leqno and fleqn.",
%%%     docstring       = "The checksum field above contains a CRC-16
%%%                        checksum as the first value, followed by the
%%%                        equivalent of the standard UNIX wc (word
%%%                        count) utility output of lines, words, and
%%%                        characters.  This is produced by Robert
%%%                        Solovay's checksum utility.",
%%%  }
%%% ====================================================================
%
% Subeqnarray package to use with LaTeX2e
%
% Copyright (C) 1988--1994 by Johannes Braams, PTT Research
%                          all rights resserved
%
% 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
%     subeqnaray.dtx.
%
% Error reports please to: J. Braams
%                          PTT Research
%                          St. Paulusstraat 4
%                          2264 XZ Leidschendam
%                          The Netherlands
%                  Email:  <J.L.Braams@research.ptt.nl>
%
% \section{Producing the documentation}
%
%    A short driver is provided that can be extracted if necessary by
%    the \textsf{DocStrip} program provided with \LaTeXe.
%    \begin{macrocode}
%<*driver>
\documentclass{ltxdoc}

\pagestyle{myheadings}
\EnableCrossrefs

\RecordChanges

\newcommand\Lopt[1]{\textsf{#1}}
\makeatletter
\renewenvironment{theglossary}{%
    \glossary@prologue%
    \GlossaryParms \let\item\@idxitem \ignorespaces}%
   {}
\makeatother
\begin{document}

\DocInput{subeqnarray.dtx}
\newpage
\PrintIndex
\PrintChanges
\end{document}
%</driver>
%    \end{macrocode}
%\fi
%
%
% \title{Numbering individual lines of equation array's}
%
% \author{Johannes Braams\\
%         PTT Research\\
%         Sint Paulusstraat 4\\
%         2264 XZ Leidschendam\\
%         The Netherlands\\
%         Internet: \texttt{J.L.Braams@research.ptt.nl}}
%
% \date{February 9, 1994}
%
% \markboth
%      {subeqnarray package version \fileversion as of \filedate}
%      {subeqnarray package version \fileversion as of \filedate}
%
% \maketitle
%
%
%    This package defines the \texttt{subeqnarray} and
%    \texttt{subeqnarray*} environments, which behave like the
%    equivalent \texttt{eqnarray} and \texttt{eqnarray*} environments,
%    except that the individual lines are numbered like 1a, 1b, 1c,
%    etc.
%
%    To refer to these numbers an extra label command |\slabel|
%    has been defined.
%
%    Many of this code was taken from \texttt{latex.tex} and modified
%    for  this purpose.
%
% \StopEventually{}
%
% \changes{1.1}{1988/12/22}{Fixed bug in subeqnarray* environment}
% \changes{2.0}{1993/11/02}{Added support for the leqno option}
% \changes{2.0}{1993/11/02}{Added support for the fleqn  option}
% \changes{2.1}{1994/02/09}{Upgrade for LaTeX2e}
%
% \section{Identification}
%
%    The first thing to do is identify this package to \LaTeX\
%    \begin{macrocode}
%<*package>
\ProvidesPackage{subeqnarray}[\filedate\space subeqnarray package]
%    \end{macrocode}
%
%    and write a note in the log file.
%    \begin{macrocode}
\wlog{Package `subeqnarray' version \fileversion\space<\filedate> (JLB)}
\wlog{English documentation\space\space\space<\docdate> (JLB)}
%    \end{macrocode}
%
% \section{Initial Code}
%
% \begin{macro}{\c@subequation}
%    We need to allocate a new counter for the \texttt{subequation}
%    environment. It is reset by the \texttt{equation} counter.
%    \begin{macrocode}
\newcounter{subequation}[equation]
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\thesubequation}
%    The representation o the counter \texttt{subequation} includes
%    the \texttt{equation} counter
%    \begin{macrocode}
\def\thesubequation{\theequation\alph{subequation}}
%    \end{macrocode}
% \end{macro}
%
% \section{Option Handling}
%
%    The standard \LaTeX\ options \Lopt{leqno} and \Lopt{fleqn} are
%    recognised by this package.
%    \begin{macrocode}
%
%    When \Lopt{leqno} is used the equation numbers should appear on
%    the left side of the equation. The numbers are generated by
%    |\@subeqnnum| which needs a different definition to acheive this
%    effect.
%    \begin{macrocode}
\DeclareOption{leqno}{%
  \def\@subeqnnum{\hbox to .01\p@{}\rlap{\reset@font\rmfamily
        \hskip -\displaywidth(\thesubequation)}}}
%    \end{macrocode}
%    The default definition of |\@subeqnnum|.
%    \begin{macrocode}
\DeclareOption{reqno}{%
  \def\@subeqnnum{{\reset@font\rmfamily (\thesubequation)}}}
%    \end{macrocode}
%
%    When the option \Lopt{fleqn} is used, the equations have to be
%    printed flush left, with an indent of |\mathindent|; the
%    equations are seperated from the surrounding text by |\topsep|
%    (plus |\partopsep| if necessary) and the width of the display is
%    |\linewidth|.
%    \begin{macrocode}
\DeclareOption{fleqn}{%
  \def\subeqn@start{%
    \tabskip\mathindent
    \abovedisplayskip\topsep
    \ifvmode\advance\abovedisplayskip\partopsep\fi
    \belowdisplayskip\abovedisplayskip
    \belowdisplayshortskip\abovedisplayskip
    \abovedisplayshortskip\abovedisplayskip
    $$\everycr{}\halign to \linewidth}}% $$
%    \end{macrocode}
%
%    The default will be to have displayed equations to the width of
%    |\displaywidth|.
%    \begin{macrocode}
\DeclareOption{deqn}{%
  \def\subeqn@start{%
    \tabskip\@centering
    $$\everycr{}\halign to \displaywidth}}% $$
%    \end{macrocode}
%
%    We don't support any other options
%    \begin{macrocode}
\DeclareOption*{\OptionNotUsed}
%    \end{macrocode}
%
% \section{Executing Options}
%
%    Make sure the |\@eqnnum| is defined by specifying \Lopt{reqno} as
%    a default option. Specifying \Lopt{deqn} as a default option
%    defines |\subeqn@start|.
%    \begin{macrocode}
\ExecuteOptions{reqno,deqn}
%    \end{macrocode}
%
%    Now see if the use specified any options.
%    \begin{macrocode}
\ProcessOptions
%    \end{macrocode}
%
% \section{The main code}
%
% \begin{macro}{\slabel}
%    A new label command to refer to subequations. It works
%    like the |\label| command and was taken from \texttt{latex.tex}.
%
%  |\slabel{FOO}| writes the following on file |\@auxout|
%
%  |\newlabel{FOO}{{eval(\@currentlabel)}{eval(\thepage)}}|
%
%    \begin{macrocode}
\newcommand\slabel[1]{%
  \@bsphack
  \if@filesw
    {\let\thepage\relax
     \def\protect{\noexpand\noexpand\noexpand}%
     \edef\@tempa{\write\@auxout{\string
        \newlabel{#1}{{\thesubequation}{\thepage}}}}%
     \expandafter}\@tempa
     \if@nobreak \ifvmode\nobreak\fi\fi
  \fi\@esphack}
%    \end{macrocode}
% \end{macro}
%
% \begin{environment}{subeqnarray}
%    The \texttt{subeqnarray} environment steps the equation counter,
%    sets the subequation counter equal to 1 and behaves much like the
%    \texttt{eqnarray} environment. Note the |\@currentlabel| is
%    defined to use the equation counter. This is done so that an
%    entire array an be referred to using the value of the equation
%    counter. Hence the need for the |\slabel| command.
%
%    \begin{macrocode}
\newenvironment{subeqnarray}%
   {\stepcounter{equation}%
    \def\@currentlabel{\p@equation\theequation}%
    \global\c@subequation\@ne
    \global\@eqnswtrue\m@th
    \global\@eqcnt\z@\let\\\@subeqncr
    \subeqn@start
     \bgroup\hskip\@centering
      $\displaystyle\tabskip\z@skip{##}$\@eqnsel
      &\global\@eqcnt\@ne \hskip \tw@\arraycolsep \hfil${##}$\hfil
      &\global\@eqcnt\tw@ \hskip \tw@\arraycolsep
         $\displaystyle{##}$\hfil \tabskip\@centering
      &\global\@eqcnt\thr@@
         \hbox to\z@\bgroup\hss##\egroup\tabskip\z@skip\cr}
   {\@@subeqncr\egroup $$\global\@ignoretrue}
%    \end{macrocode}
% \end{environment}
%
% \begin{macro}{\@subeqncr}
%    These macros handle the user command |\\|; they are adapted from
%    the ones used or the \texttt{eqnarray} environment.
%
%    First the presence of a \texttt{*} detected and the right penalty
%    selected.
%    \begin{macrocode}
\def\@subeqncr{{\ifnum0=`}\fi\@ifstar{\global\@eqpen\@M
    \@ysubeqncr}{\global\@eqpen\interdisplaylinepenalty \@ysubeqncr}}
%    \end{macrocode}
%
% \begin{macro}{@ysubeqncr}
%    This macro is called by |\@subeqncr| and checks if the user
%    requested any extra vertical space. It calls |\@xsubeqncr| with
%    the wanted amount of space as its argument.
%    \begin{macrocode}
\def\@ysubeqncr{\@ifnextchar [{\@xsubeqncr}{\@xsubeqncr[\z@skip]}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@xsubeqncr}
%    This macro calls |\@@subeqncr| to put in extra |&|'s if needed,
%    generating an error if the number of columns is too large. Then
%    the penalty selected earlier and the white space requested are
%    inserted.
%    \begin{macrocode}
\def\@xsubeqncr[#1]{\ifnum0=`{\fi}\@@subeqncr
   \noalign{\penalty\@eqpen\vskip\jot\vskip #1\relax}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@subeqncr}
%    Ceck the number of columns, and insert extra |&| if needed. If
%    there appear to be more than 3 columns an error is signalled.
%    \begin{macrocode}
\def\@@subeqncr{\let\@tempa\relax
    \ifcase\@eqcnt \def\@tempa{& & &}\or \def\@tempa{& &}
      \or \def\@tempa{&}\else
       \let\@tempa\@empty
       \@latexerr{Too many columns in subeqnarray environment}\@ehc\fi
     \@tempa \if@eqnsw\@subeqnnum\refstepcounter{subequation}\fi
     \global\@eqnswtrue\global\@eqcnt\z@\cr}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{environment}{subeqnarray*}
%    This environment is basically the same as the \texttt{eqnarray}
%    environment, but it is provided just or completeness.
%    \begin{macrocode}
\newenvironment{subeqnarray*}%
  {\def\@subeqncr{\nonumber\@ssubeqncr}\subeqnarray}
  {\global\advance\c@equation\m@ne\nonumber\endsubeqnarray}
%    \end{macrocode}
% \end{environment}
%
% \begin{macro}{\@ssubeqncr}
%    This is used in the \texttt{esubqnarray*} environment.
%    \begin{macrocode}
\let\@ssubeqncr\@subeqncr
%</package>
%<*sample>
%    \end{macrocode}
% \end{macro}
%
% \section{An example of the use of this package}
%
%    When you run the following document through \LaTeX\ you will see
%    the differene between the \texttt{subeqnarray} and
%    \texttt{eqnarray} environments.
%    \begin{macrocode}
%<*sample>
\documentclass[fleqn]{article}
\usepackage{subeqnarray}
\begin{document}
This document shows an example of the use of the \emph{subeqnarray}
environment. Here is one:
\begin{subeqnarray}
\label{eqw}
\slabel{eq0}
 x & = & a \times b \\
\slabel{eq1}
 & = & z + t\\
\slabel{eq2}
 & = & z + t
\end{subeqnarray}
The first equation is number~\ref{eq0}, the last is~\ref{eq2}. The
equation as a whole can be referred to as equation~\ref{eqw}.

To show that equation numbers behave normally, here's an
\emph{eqnarray} environment.
\begin{eqnarray}
\label{eq10}
 x & = & a \times b \\
\label{eq11}
 & = & z + t\\
\label{eq12}
 & = & z + t
\end{eqnarray}

These are equations~\ref{eq10},~\ref{eq11} and~\ref{eq12}.
\end{document}
%</sample>
%    \end{macrocode}
%
% \Finale
\endinput
%
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%%  {Upper-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
%%   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
%%   Exclamation   \!     Double quote  \"     Hash (number) \#
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%%   Acute accent  \'     Left paren    \(     Right paren   \)
%%   Asterisk      \*     Plus          \+     Comma         \,
%%   Minus         \-     Point         \.     Solidus       \/
%%   Colon         \:     Semicolon     \;     Less than     \<
%%   Equals        \=     Greater than  \>     Question mark \?
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%%   Right bracket \]     Circumflex    \^     Underscore    \_
%%   Grave accent  \`     Left brace    \{     Vertical bar  \|
%%   Right brace   \}     Tilde         \~}
%%