How to make \@abspage@last work as the number of total pages

Question

By the following codes, I expect to typeset a pdf file of two pages. In the frist page, I want to print (1)(2).

But it does not work. I guess this is because of the wrong use of the LaTeX macro \@abspage@last, or wrong use of compiler option argument. Anyone has ideas to make it work?

Codes:

\documentclass{article}
\usepackage{pgffor}
\makeatletter
\newcommand{\lastpagenumber}{\@abspage@last}
\makeatother
%\newcommand{\lastpagenumberA}{\PreviousTotalPages}
\begin{document}
\foreach \i in {1,...,\lastpagenumber}{(\i)}
%\rule{\numexpr 4/\lastpagenumberA\relax in}{5pt}
\clearpage\mbox{}
\end{document}

Answer 1

When the .aux file doesn't exist, \@abspage@last is set to 1073741823 and of course you don't want to produce that many pages.

So, let's try and “fix” by telling LaTeX that if \@abspage@last equals \maxdimen we set \lastpagenumber to, say, zero.

\documentclass{article}
\usepackage{pgffor}
\makeatletter
\newcommand{\lastpagenumber}{%
  \ifnum@abspage@last=\maxdimen
    \expandafter 0%
  \else
    \expandafter@abspage@last
  \fi
}
\makeatother
\begin{document}
\foreach \i in {1,...,\lastpagenumber}{(\i)}
\clearpage
\mbox{LAST}
\end{document}

Now, if the .aux file doesn't exist (or, for some reason, it doesn't set a value for \@abspage@last), you get two pages. The first page has “(1)(0)” (because of how \foreach works) and the second one has “LAST”.

OK, now the .aux file exists and contains

\gdef \@abspage@last{2}

We run again LaTeX to get “(1)(2)” in the first page and “LAST” in the second one.

Perhaps even better, as it avoids one expansion step when using \lastpagenumber:

\documentclass{article}
\usepackage{pgffor}
\makeatletter
\newcommand{\lastpagenumber}{}
\AtBeginDocument{%
  \ifnum@abspage@last=\maxdimen
    \def\lastpagenumber{0}%
  \else
    \let\lastpagenumber@abspage@last
  \fi
}
\makeatother
\begin{document}
\foreach \i in {1,...,\lastpagenumber}{(\i)}
\clearpage
\mbox{LAST}
\end{document}

I do \newcommand{\lastpagenumber}{} for safety: if some package you load defines \lastpagenumber, you get an error and you know you cannot use this command.

Next, after the .aux file is read in (provided it exists), we check whether \@abspage@last is \maxdimen; in this case we define \lastpagenumber to expand to 0, otherwise we make it equal to \@abspage@last.

Answer 2

you can say:

\documentclass{article}
\ExplSyntaxOn
\iow_new:N \l_lastpage_file 
\file_if_exist:nTF{\c_sys_jobname_str.page}
{
  \file_input:n{\c_sys_jobname_str.page}
}
{
  % \cs_set_eq:NN \lastpage \relax
  \cs_set:Npn \lastpage {1}
}
\AtEndDocument{
\iow_open:Nn \l_lastpage_file{\c_sys_jobname_str.page}
\iow_now:Nx \l_lastpage_file 
{
  \cs_set:Npn \exp_not:N \lastpage 
  {
    \thepage
  }
}
\iow_close:N \l_lastpage_file 
}
\ExplSyntaxOff
\usepackage{pgffor}
\begin{document}
\foreach \i in {1,...,\lastpage}{(\i)}
\rule{\numexpr 4/\lastpage\relax in}{5pt}
\newpage
test
\foreach \i in {1,...,\lastpage}{(\i)}
\rule{\numexpr 4/\lastpage\relax in}{5pt}
\newpage
test
\foreach \i in {1,...,\lastpage}{(\i)}
\rule{\numexpr 4/\lastpage\relax in}{5pt}
\end{document}

---

This also works, but it still needs to be compiled twice!

\documentclass{article}
\usepackage{pgffor}
\begin{document}
\makeatletter
\ifnum\@abspage@last > 1000
\newcommand{\lastpagenumber}{1}
\else
\newcommand{\lastpagenumber}{\@abspage@last}
\fi
\makeatother
\foreach \i in {1,...,\lastpagenumber}{(\i)}
AA
%\rule{\numexpr 4/\lastpagenumberA\relax in}{5pt}
\clearpage\mbox{}
\end{document}