\documentstyle{ltugboat}
\emergencystretch1in
\title{Correction sheets in \LaTeX}
\author{Mike Piff}
\address{Department of Pure Mathematics\\University of Sheffield\\Sheffield
   S10 2TN\\England}
\netaddress[\network{Janet}]{pm1mjp@pa.shef.ac.uk}
\begin{document}
\maketitle
\begin{abstract}
   In this article the author explains how to produce minor correction
   sheets to a \LaTeX\ book.
   The sort of corrections handled are those which
   involve changes to a few words or possibly rewriting a few lines on a page,
   but not the sort that would cause \TeX\ to reformat the whole book because
   a page has stretched or shrunk too much. The
   author has used these macros for corrections to a book in print, but they
   could equally well make the last stages of proof reading
   and correction less irksome.
\end{abstract}
\section{Introduction}
Reprinting individual pages of a \LaTeX\ book for correction
can be quite a tricky task. One can always process the whole book again,
but chances are that the page breaks will all be different. This can also
cause
cross-references and the index to be inaccurate, and so is
not really suitable unless the whole book is being reset.

The following style option \verb"corrections.sty" makes the job easier.
It was developed in particular for the author's needs,
but should be easy to customize.

\section{The style in use}
It is assumed that a root file is available to produce the book.
Make a copy of this,
and insert the correction style option, and also the commands
\begin{verbatim}
\correctionsonly
\renewcommand{\resetcounters}[2]{%
   \setcounter{Theorem}{#1}%
   \setcounter{Example}{#2}%
   \ignorespaces}
\end{verbatim}
in the preamble. The former is to tell \LaTeX\ to produce only correction
sheets, and the latter is customized to the particular counters being
used in the
current book---in this case, theorem and example counters.
We must either make a copy of the \verb"aux" file from the original book,
or carefully replace
any \verb"\ref" and \verb"\pageref" commands with
their expansions in the corrections file. The author's own preference was the
latter; he changed his root file so that it actually contained the pages to be
printed, rather than have to \verb"\input" or \verb"\include" copies of each
chapter file and \verb"aux" file. As a precaution, he also redefined \verb"\ref"
and \verb"\pageref" so as to give an error message.

Most of the body of the book may now be discarded.
In its place, we put instructions to print individual pages.
At least the text of these pages must be retained.
But this is where the complications begin, since it is possible to be heavily
nested within several layers of environments at the start of a page, as well
as being mid-paragraph in section~9 of chapter~4, and about to produce
Example~4.97 and Theorem~4.25. Moreover, at the end of the page we may be in
a different paragraph and a different section. The headers on the pages will
have to reflect the current state, and the page must finish flush right.

None of these problems is of much significance in itself, but the
combination of all of them means that we have to be pretty careful in giving
the exact state of the book for each page. Some counters change rapidly from
page to page, whereas some change more slowly. I have divided them
accordingly, and provide explicit commands to reset the slow counters, such
as \verb"chapter" and \verb"section", whilst allowing the individual page
instruction to reset the quicker moving sort, such as \verb"Theorem" or
\verb"Example".

The instructions
\begin{verbatim}
\currentstate{chapter}{4}%
   {The theory of relaxors}
\currentstate{section}{9}%
   {Covariant relaxors}
\end{verbatim}
tell \LaTeX\ that we are firmly in chapter~4, section~9. \LaTeX\ now needs to
know how many theorems and examples are behind us. We will tell it at the start
of the next page.

But first we need to inform \LaTeX\ of the current state
of nesting of environments
at the top of the next page.
We can do this either by leaving the immediately
preceding text in, or by just giving it a clue like this.
\begin{verbatim}
\begin{enumerate}
   \item \mbox{}
   \item \mbox{}
   \item
      \begin{itemize}
         \item\mbox{}
         %%This is the text that
         %%immediately preceded the curr-
\end{verbatim}
The paragraph is clearly in full flow, and so we tell \LaTeX\ to start the page
flush left, where ``left'' means according to the level of indentation of
environments.
\begin{verbatim}
\startpageflushleft{101}{24}{96}%
   -ent page.
   Now we are producing page~101.
   The next theorem will be~25.
   The next example will be~97.
\end{verbatim}
There is also a similar \verb"\startpage" command to produce a normally
indented paragraph at the top of the page, or to use if the first thing
on the page is a theorem, say.

This page ends in mid-flow, so we let \LaTeX\ know about this.
\begin{verbatim}
   ...it was clearly not too diff-%
   \endpageflushright.
\end{verbatim}
The \verb"\endpage" command has a similar meaning, but allows normal
paragraph termination in mid-line. Both cause the page to end flush bottom.
Just use \verb"\clearpage" if this page is at the end of a chapter.

It may happen that a run of two or more pages have mistakes on them. The macros
in the style option are designed to make that easier to handle. At the start of
a second, or subsequent, page in mid-paragraph, insert the instruction
\begin{verbatim}
\anotherpageflushleft
\end{verbatim}
or include the command \verb"\anotherpage" in its text if it does not have to
start flush left.
Terminate any such pages in the usual way.
This saves having to retype the
current state of the fast moving counters.

The author has found that floating figures are handled correctly, but \TeX\
has to see the whole page where the figure is defined. Alternatively,
the figure can be moved to an appropriate place on the page being printed.
Clearly a large number of held-over insertions could present some problems,
and the best course of action might then be to move them to the exact place
where they should appear, with the ``insert here'' option active.

Footnotes on the current page can be handled by using the optional
parameter to set the correct mark. Footnotes held over wholly from a
previous page can be inserted with \verb"\footnotetext".
A split footnote from a previous page is handled by means of the
\verb"\morefootnotetext" command, which takes the text of the footnote
as its only parameter.

The final feature of this style option is the fact that {\em only\/} the pages
specified above get through to the \verb"dvi" file.

\section{The style in detail}

We first of all define two boolean variables. The variable
\verb"\ifcorrections" is an indicator of
whether we are producing corrections or not. Its default is false, so the
style will have no effect unless it is changed to true.
Variable \verb"\ifrealpage" is used internally to tell \LaTeX\ to
actually ship out the current page. Its default is true.
\begin{verbatim}
\newif\ifcorrections \correctionsfalse
\newif\ifrealpage \realpagetrue
\end{verbatim}
To switch from this default mode, where the style has no effect, we provide
a command to change the values of these two variables.
\begin{verbatim}
\def\correctionsonly{%
   \correctionstrue \realpagefalse}
\end{verbatim}

The sectioning counters can be changed by means of the \verb"\currentstate"
command. We provide some dummy text by means of the
\verb"\mbox{}" command.
\begin{verbatim}
\def\currentstate#1#2#3{%
   \setcounter{#1}{#2}%
   \addtocounter{#1}{-1}%
   \csname #1\endcsname{#3}\mbox{}}%
\end{verbatim}

To start  a page of output, we specify the page number and then call a
command \verb"\resetcounters", whose default meaning is to do
nothing but ignore spaces.
This command should be redefined in the user's
preamble to take account of any counters that might
need updating.
\begin{verbatim}
\def\startpage#1{\npage{#1}%
   \resetcounters}
\def\startpageflushleft#1{\npage{#1}%
   \noindent\resetcounters}
\newcommand{\resetcounters}{\ignorespaces}
\end{verbatim}

Both commands to produce a new page make use of the \verb"\npage" command.
\begin{verbatim}
\def\npage#1{\clearpage
   \global\realpagetrue
   \setcounter{page}{#1}}
\end{verbatim}

The end of a page, flush right or not, is produced by the following two
commands, or if appropriate by a \verb"\clearpage".
\begin{verbatim}
\def\endpageflushright{%
   {\parfillskip0pt\par\pagebreak}}
\def\endpage{\pagebreak}
\end{verbatim}
If the page after this one also needs to be printed, an alternative way
of producing it is to use one of the following two commands.
\begin{verbatim}
\def\anotherpageflushleft{%
   \global\realpagetrue\noindent}
\def\anotherpage{\global\realpagetrue}
\end{verbatim}

A footnote from the previous page, part of which appears at the bottom of
the current page, can be handled by inserting a left justified
footnote without a mark in either the text or the footnote itself.
This command should be invisible in the surrounding text, and so we make
certain that it does not alter \TeX' space factor.
\begin{verbatim}
\def\morefootnotetext#1{\@bsphack{%
   \def\@makefntext##1{\noindent ##1}%
   \footnotetext{#1}}\@esphack}
\end{verbatim}

The only thing that remains is to make sure that any extraneous text, such
as is created by sectioning commands, is not printed. We first take a copy
of the \LaTeX\ command that actually ships a page to the \verb"dvi" file.
\begin{verbatim}
\let\@@outputpage\@outputpage
\end{verbatim}
The command \verb"\@outputpage" is then redefined in terms of its old
meaning. First, only ``real'' pages are printed, that is, only when
\verb"\ifrealpage" returns true. Then, if we are only printing correction
sheets, we immediately switch off printing of pages after this one.
Only the \verb"\startpage" and \verb"\anotherpage" commands will switch
printing on again.

Note that we need to ensure that any special page style
set by \verb"\thispagestyle" on a page that has not been printed
does not carry over to the following page.
For instance, a \verb"\chapter" command will generally introduce a
\verb"plain" page style command into the document.

The command \verb"\@outputpage" should otherwise do everything that its old
version did, apart from shipping the page out to the \verb"dvi" file.
\begin{verbatim}
\def\@outputpage{%
   \ifrealpage\@@outputpage
   \else\global\@specialpagefalse
   \let\firstmark\botmark\fi
   \ifcorrections\global\realpagefalse\fi}
\end{verbatim}
\makesignature
\end{document}

%%% CORRECTION.STY

\typeout{Corrections style option for LaTeX, (c) Mike Piff, 07/22/92}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Dr M J Piff                      %%  e-mail:
%% Department of Pure Mathematics   %%
%% University of Sheffield          %%  M.Piff@sheffield.ac.uk
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