% $StyleId: footnpag.doc,v 2.6 1995/11/10 18:21:26 schrod Exp $
%----------------------------------------------------------------------
% Written by Joachim Schrod <schrod@iti.informatik.th-darmstadt.de>.
% Copyright conditions see below.

%
% LaTeX package footnpag
% numbers footnotes subsequently per page
%
% [LaTeX in MAKEPROG]
% (history at end)

% If you have received this style file without the user manual (in the
% file footnpag-user.tex or the respective DVI file), it's incomplete and
% near to useless. If it was given to you as something that you shall
% use as an author -- complain bitterly to your provider. You need the
% documentation and you have a right on it! (Below you can find info
% where to get the reference version.)




\documentclass{progltx}

\usepackage{footnpag-doc}		% document-specific markup
\usepackage{fullpage}


\nofiles				% no cross references


\RCS $StyleDate: 1995/11/10 18:21:26 $


\begin{document}


\title{The \texttt{footnpag} Package\\
    {\large (Implementation)}%
    }
\author{%			% LaTeX does not discard unnecessary glue...
    Joachim Schrod%
    \thanks{%
	\protect\raggedright
	TU~Darmstadt, Computer Science Department, WG Systems Programming,
	Alexanderstr.~10, D-64283~Darmstadt, Germany.
	Email: \texttt{schrod@iti.informatik.th-darmstadt.de}.%
	}%
    }
\date{%
    Revision \RCSStyleRevision\\
    (as of \RCSStyleDate)%
    }

\maketitle


% doesn't work with progltx yet
%\tableofcontents



% ------------------------------------------------------------
%
% subdocument: The user interface of footnpag.sty
%

\input{footnpag-user}

%
% ------------------------------------------------------------
%
% subdocument: The internal interface
%

%\input{footnpag-conf}

%
% ------------------------------------------------------------



\chap Implementation.

Please note, that this package was originally written for plain
\TeX{}. The original version is still available. This version will
evolve, and will finally be full \LaTeX{} code.

This module reserves the namespace |fnpp|. Due to the age of the code
it does not obey the namespace throughout, this has to be changed in a
future revision.

\beginprog
\ifx \fnpp@loaded\undefined
    \def\fnpp@loaded{$StyleRevision: 2.6 $}
\else
    \PackageWarningNoLine{footnpag}%
        {Some other package already uses namespace `fnpp'}
\fi
\endprog


\sect Let's identify this package.

The code below is explained in the implementation documentation of the
|rcs| package.

\beginprog
\begingroup
    \def\RCSPackage#1#2 $#3: #4 #5\endRCS $#6: #7 #8\endRCS{%
	\def\date{#4}\def\id{v#7}%
	\ProvidesPackage{#1}[\date\space\id\space #2]%
	}

  \RCSPackage{footnpag}{numbering footnotes per page}
  $StyleDate: 1995/11/10 18:21:26 $: 9999/00/00 \endRCS
  $StyleRevision: 2.6 $: 0.0 \endRCS
\endgroup
\endprog


\sect This module is supported. Send bug reports, comments and
repairs.

The reference version may be retrieved via anonymous ftp from
|ftp.th-darmstadt.de| [130.83.47.112], directory |pub/tex/latex|. It's
placed there as a gzipped tar file. (The information on the IP~number
is dated August~3,~1995.
It might have changed, although this is very unlikely. Use your
friendly nameserver.)


\sect This is freely distributable software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version~2 of the
License, or (at your option) any later version.

This software is distributed in the hope that it will be useful, but
\textbf{without any warranty}; without even the implied warranty of
\textbf{merchantability} or \textbf{fitness for a particular purpose}.
See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License in
the file |License| along with this package; if not, write to the Free
Software Foundation, Inc., 675~Mass Ave, Cambridge, MA~02139,~USA.


\sect Before we start we declare some shorthands for category codes.
By declaring the underscore~`(|_|)' as letter we can use it in our
macros. (I agree with \textsc{D.~Knuth} that
|\identifier_several_words_long| is more readable than
|\IdentifierSeveralWordsLong| and in every case better than |\p@@@s|.)

As this is a \LaTeX{} module the at sign is a letter anyhow; so
we can use the ``private'' \LaTeX{} macros; and with the underscore we
can make our own macros more readable.  But as we have to restore this
category code at the end of this macro file we store its former value
in the control sequence |\CatUsCode|. This method is better than to
use a group because not all macros have to be defined global this way.

Since somebody might use more modules from me, this cseqs might be
defined already.

\beginprog
\ifx \CatEscape\undefined
    \chardef\CatEscape=0
    \chardef\CatOpen=1
    \chardef\CatClose=2
    \chardef\CatIgnore=9
    \chardef\CatLetter=11
    \chardef\CatOther=12
    \chardef\CatActive=13		% is defined in Plain already

    \chardef\CatUsCode=\catcode`\_
\fi

\catcode`\_=\CatLetter			% top level macro file
\endprog


\sect Let's regard the implementation strategy. Because
the contents of one page is determined at (nearly) random places
with an asynchronous invogation of the output routine, we can not
give numbers to every footnote subsequently between output and
output: a footnote at the top of a page will perhaps get a number
before the output is triggered and there is no way to change this
number. The problem is like forward references to text places and it
is solved in a similar fashion. We need two \TeX{} runs to get the
numbering right but this is acceptable (who's got a finished text
after one run?!). In the first run we gather up in a file the
information where the footnotes are standing and in the second run
we use this information.

We must identify all footnotes if we write their numbers to the
footnote file, so each footnote gets an unary name built with the
counter |\foot_name_no|. The name is `|f@|\<nameno>', where \<nameno>
is the footnote name number. This name building scheme has several
disadvantages, e.g.\ the insertion of a new footnote destroys the
knowledge of the former run about the following footnotes. If we would
have some knowledge about the document type we are using and the macro
set which is in effect we could insert other counters (e.g.\ the
chapter numbers) as well.



\chap Determing the footnote numbers.

Let's start with the initialization of the macro
set. We need a file descriptor, |\foot_file|, which we use for the
file interaction. The name of the file is built from the job name and
the suffix `|.fot|' (I hope that no macro package uses this suffix).
The |\init_footnote| macro reads the contents
of the footnote file if it exists (|\ifeof| returns true if the file
doesn't exist). The description of the reading of this file
(|\read_foot_file|) is deferred until we know the structure of the
contents. After reading, the file is closed and we can open it for
writing. For security, i.e.\ to have a defined minimal contents, we
immediately write |\relax| to the file. In the end the macro defines
itself to |\relax| to allow calling it again.

\beginprog
\newread\old_foot_file
\newwrite\foot_file
\def\foot_file_name{\jobname.fot\relax}
\def\init_footnote{%
   \openin\old_foot_file\foot_file_name
   \ifeof\old_foot_file  \closein\old_foot_file
   \else  \closein\old_foot_file
      \read_foot_file
   \fi
   \immediate\openout\foot_file\foot_file_name
   \immediate\write\foot_file{\relax}%
   \global\let\init_footnote\relax
   }
\endprog


\sect Remember, that we use |\foot_name_no| for the generation of a
name for each footnote.  The actual number of the footnote mark is
stored in |\c@footnote|, the \LaTeX{} footnote counter.

In the beginning of every footnote |\init_footnote| is called to
guarantee that the handling is initialized (this especially means
that the footnote numbers are read in by the first footnote).

\beginprog
\newcount\foot_name_no  % for generating footnote mark names
\endprog


\sect It remains an open problem how to get the numbers there. The
footnote numbering must be initialized to zero in the output routine
and every footnote must increment this footnote number. The only
thing that is expanded during the output process is the output
routine itself and the |\write|'s, but the expanded tokens of
|\write| are written out, not interpreted. Well, the idea is simple:
We defer the counting to the second run and write the instructions
that do this to the file. The counting is then done while reading
the footnote file.

\noindent That means that the output routine adds entries like
%
\begin{quote}
|\c@footnote = 0|
\end{quote}
%
and every footnote adds an entry that looks like
%
\begin{quote}
|\advance\c@footnote by 1|\\
|\xdef\csname f@|\<nameno> |\endcsname{\number\c@footnote}|
\end{quote}
%
where \<nameno> is replaced by the current footnote name number.


\sect The macro |\fnpp_next_footnote| determines the next footnote
number and stores it in |\c@footnote|, the official \LaTeX{} footnote
counter. This counter is used since |\footnotetext| constructs the
mark in the footnote text from it. One can say that
|\fnpp_next_footnote| is a non-typical way to step this counter, it's
a series iterator instead of an incrementer like |\stepcounter|.

The expansion of |\foot_name_no| must not be postponed until |\output|
time because there may be more footnotes coming on this page that'll
increase this number.
Therefore we first define the macro |\do_write| which contains the
|\write| and the expanded tokens which are to be put out. Every token
that should not be expanded is prefixed by |\string| (resulting in
character tokens that represent the token name). A |\space| must be
inserted to separate |\csname| from |f|. The |\xdef| in the (written)
definition code of |f@|\<nameno> is needed because the footnote file
will be read in within a group.

After writing the entry to the footnote file the number for this
footnote is set to~0 if it is not already defined (from a previous
run).

\beginprog
\def\fnpp_next_footnote{%
    \init_footnote
    \global\advance\foot_name_no\@ne
    \edef\do_write{%
	\write\foot_file{%
	    \string\advance\c@footnote\@ne
	    \string\expandafter\xdef
			\string\csname\space f@\number\foot_name_no \endcsname{%
		\string\number\c@footnote
		}%
	    }%
	}%
    \do_write
    \global\c@footnote 0\csname f@\number\foot_name_no \endcsname \relax
    }
\endprog


\sect It remains the reading of the footnote file. We have to read in
macros with names containing `|@|' characters. This will be done in
horizontal mode, so we ignore lineends to discard undesired spaces.

\beginprog
\def\read_foot_file{%
   \begingroup
      \catcode`\@\CatLetter \catcode`\^^M\CatIgnore
      \input \foot_file_name
   \endgroup
   }
\endprog




\chap Connection to the output routine.

We must write the footnote number reset code at the start of each new
page. The most easy way to do this is to add an |\immediate\write|
to the output routine.

The output routine has no associated hook. (It should, of course. This
is no exotic wish.)  So we have to add our code to it by redefining
some cseq. In a former version we really rebound |\output|, but that
was a leftover from the plain \TeX{} version. Then we had to check for
special |\output| invocations, which column we're in, etc. Now we rely
on some internals of \LaTeX{}: |\@outputpage| does the real ship out,
we just prepend our write to the front.

The reset code must not be written when no footnote was given by now.
We can check for the binding of |\init_footnote| to detect this, it's
|\relax| after the first footnote.

\beginprog
\let\fnpp_orig_outputpage=\@outputpage
\def\@outputpage{%
    \ifx \init_footnote\relax
	\immediate\write\foot_file{\c@footnote\z@}%
    \fi
    \fnpp_orig_outputpage
    }
\endprog




\chap The user interface.

Footnotes may be produced by |\footnote|, or by |\footnotemark| and
|\footnotetext| (the former creates the mark, the latter the text with
the last mark). All these tags have an optional argument, a number
that shall be used to create the mark for this specific invocation.

We redefine only the handling of macro invocations without optional
arguments. The original bindings are made available in the protected
interface, in case footnotes are used for unusual things. (See the
chunk on title matters below, for an example.)

\beginprog
\let\FnppOrigFootnote=\footnote		% save original bindings
\let\FnppOrigFootnotemark=\footnotemark

\def\footnote{%
    \@ifnextchar[%			% ] (Emacs)
	\@xfootnote
	{\fnpp_next_footnote \@xfootnote[\the\c@footnote]}%
    }
\def\footnotemark{%
    \@ifnextchar[%			% ] (Emacs)
	\@xfootnotemark
	{\fnpp_next_footnote \@xfootnotemark[\the\c@footnote]}%
    }
\endprog


\sect Footnote tags in minipages behave a bit differently: There
|\footnote| and |\footnotetext| create minipage-local footnotes,
whereas |\footnotemark| creates a `global' footnote mark. I.e., if one
wants to make a footnote in a minipage that shall go on the page, one
has to specify |\footnotemark| in the minipage and |\footnotetext|
thereafter. |\footnotetext| uses the current value of the footnote
counter, since we set it by |\fnpp_next_footnote|, everything will
work.

\LaTeX{} makes a hook available to setup the minipage enviroment. But
the hook is initialized in a way that their own hook-enhancement
function does not work, we have to repair it first. No comment\,\dots

\beginprog
\ifx \@minipagerestore\relax
    \let\@minipagerestore\@empty
\fi

\g@addto@macro\@minipagerestore{%
    \let\footnote\FnppOrigFootnote
    }
\endprog


\sect But footnotes are used for other things, too. E.g., to mention
affiliation or acknowledgements in title matters. This is done by
|\thanks| that uses |\footnotemark| to construct the respective marks.
The expansion of |\thanks| is done by |\maketitle| that resets the
footnote counter afterwards. But that reset does not work with this
package, as the footnote counter value is not used to determine the
next one.

The most simple solution is to reset |\footnotemark| during the
evaluation of |\maketitle|. We can do that in a group since all
side-effects of |\maketitle| should be global anyhow.

\beginprog
\let\fnpp_orig_maketitle=\maketitle
\def\maketitle{%
    \begingroup
    	\let\footnotemark\FnppOrigFootnotemark
	\fnpp_orig_maketitle
    \endgroup
    }
\endprog





\chap The end.

Well, after all we're finished with this module. We must not forget to
restore the underscore catcode.

\beginprog
\catcode`\_=\CatUsCode

\endinput
\endprog


\sect I would like to thank those who helped me to improve this style.
% In particular, XXX provided XXXsubstantial parts of the code.

\textsc{Chris Thompson} sent change proposals that made the code more
robust.

\textsc{Frank Mittelbach} gave the impulse to make real \LaTeX{}
code out of the former plain \TeX{} code. (Actually, that's not as
drastic as it sounds. I threw half the code away and used stuff
already supplied by the \LaTeX{} kernel, then I added a few lines to
take care of minipages and front matter.)

\textsc{John Lu},
\textsc{Sebastian Rahtz},
and
\textsc{Frank Thomas}
provided error and problem reports.



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\vskip\PltxPreSectSkip

\begin{rcslog}
$StyleLog: footnpag.doc,v $
\Revision 2.6 1995/11/10 18:21:26 schrod
    Make |\footnotetext| usable in |minipage| environment, again.\\
Problem reported by Sebastian Rahtz \path|<s.rahtz@elsevier.co.uk>|.

\Revision 2.5 1995/08/04 00:18:34 schrod
Made a \LaTeXe{} package from this style option.

User manual is a separate document now, that's better for
installation. Started to change the distribution into one that
conforms to the `supported bundle guidelines.'

\Revision 2.4 1995/01/01 18:54:00 schrod
Optional arguments are supported now, |\footnotemark| may be used,
footnotes in minipages and title matter are handled correctly.\\
(Enhancements requested by Frank Mittelbach
\path|<mittelbach@mzdmza.zdv.uni-mainz.de>|.)

Started rewrite to a \LaTeXe{} package. Rearranged the code, used
\LaTeX{} internals. In particular, |\@outputpage| is now redefined,
instead of |\output|. I can throw away all checks for special output
invocations, which column we're in, etc., this way. Still,
documentation changes and some minor details are missing for the next
official release.

\Revision 2.3  1994/12/31  13:26:31  schrod
Spurious messages were produced on pages without footnotes before the
first footnote. I had to check if the footnote handling is initialized.\\
(Bug reported at 25 Dec 93 by Frank Thomas \path|<frank@glocke.robin.de>|.
Actually repaired at 14 Jan 94, but change was not committed until now.)

\Revision 2.2  1993/02/02  11:04:18  schrod
If the first footnote was within a group, the footnote mechanism
was initialized a second time by the first footnote outside the group.
With this second initialization all information about previous
footnotes was discarded.\\
(Bug reported on 01 Feb 93 by John Lu \path|<luj@ecn.purdue.edu>|.)

\Revision 2.1  1991/11/07  19:58:34  schrod
Set up for a new distribution, documentation is now in LaTeX.
Added first chapter where user interface and problems are explained.

\Revision 1.2  1989/04/21  00:00:00  schrod
Advances the usability in LaTeX (|\twocolumn|),
uses an own stream for reading,
resets the counter with |\immediate\write|.
(Improvements pointed out by Chris Thompson [CET].)

\end{rcslog}


\bigskip

\noindent \textsl{Pre-RCS version history}.

\medskip

\noindent Version 1.1 removed a |\begingroup| (88-10-20).

\smallskip

\noindent Version 1.0 was released in August, 1987. Actually, it was a
posting to \TeX{}hax.



\end{document}



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Local Variables:
mode: LaTeX
TeX-brace-indent-level: 4
indent-tabs-mode: t
TeX-auto-untabify: nil
TeX-auto-regexp-list: LaTeX-auto-regexp-list
compile-command: "make footnpag.sty"
End:
