1

I would like to read the pageref info for labels directly from the Aux file. It seems that for every label <label> there is a macro \r@<label> that contains all the information and is accessible, for instance, to be used in \typeout. However, I'm interested only in the page number, so I would use \pageref{<label>}. But this doesn't work in \typeout. This is an MWE of my scenario where labels are generated using the value of a counter (updated): 

\documentclass{article}
\usepackage{lipsum,multicol,hyperref}

\makeatletter

\newcounter{mycounter}

\newcommand{\mycommand}{%
    \stepcounter{mycounter}
    \label{myitems@\themycounter}
    \typeout{Processing Item No \themycounter}
    \typeout{Label Info From Aux File Is 
        \csname r@myitems@\themycounter\endcsname}
    \typeout{Pageref From Aux File Is 
        \pageref{myitems@\themycounter}}
}

\makeatother

\begin{document}

\begin{multicols}{2}[\section{Section}]
    \mycommand
    \lipsum[1-10]
    \mycommand
    \lipsum[1-5]
    \mycommand
\end{multicols}

\end{document}

This produces the output

ProcessingItemNo1
LabelInfoFromAuxFileIs{1}{1}{Section}{section.1}{}
PagerefFromAuxFileIs\pageref {myitems@1}
[1]
ProcessingItemNo2
LabelInfoFromAuxFileIs{1}{3}{Section}{section.1}{}
PagerefFromAuxFileIs\pageref {myitems@2}
[2]
ProcessingItemNo3
LabelInfoFromAuxFileIs{1}{4}{Section}{section.1}{}
PagerefFromAuxFileIs\pageref {myitems@3}
[3] [4]

So it seems that the page information is already there at this point in the code (second token in \r@<labelname>) but \pageref cannot produce it.

My question is: How can I produce the page number at this point in the code (for use in \typeout or in other macro stuff)? Basically, I need a variable \tmpa that is fully expanded and just stores the page number for that label as restored from the AUX file. Is that possible?

Edit: After solving the problem I found that my MWE was not "minimal" enough to isolate the actual problem. So here is a simpler MWE showing what I was actually wondering about. 

\documentclass{article}
\usepackage{lipsum,multicol,hyperref}

\begin{document}

\makeatletter
% this shows that all the info on mylabel (including page number) is available:  
\typeout{Label Info From Aux File Is \r@mylabel}
% but this shows that nevertheless, \pageref does not work:  
\typeout{Last time, mylabel was on page \pageref{mylabel}}
% this is, then, the solution to my problem, see my answer below: 
\typeout{Last time, mylabel was on page \getpagerefnumber{mylabel}}
\makeatother

\begin{multicols}{2}[\section{Section}]
    \lipsum[1-10]
    \label{mylabel}
    \lipsum[1-5]
\end{multicols}
\end{document}

So, I was just wondering why \pageref doesn't work in a situation where \r@mylabel is available and stores all relevant information from the AUX file.

Improve this question
  • \refstepcounter is the macro that you need for \label, not just \stepcounter – user31729 Mar 21 '18 at 19:20
  • I don't think so as the counter is only used internally to generate the name of a new label. I don't want any \ref{label} to refer to this counter's value. – LaTechneuse Mar 22 '18 at 12:07
  • Oh no, your answer was helpful! And why does my labeling only work by chance?? – LaTechneuse Mar 22 '18 at 12:14
  • Because the page number is always stored expanded to the .aux file, regardless whether you need the real cross-reference made by \refstepcounter or just using an ordinary incrementation. Since you rely on the page number it is just by chance that this is done anyway. (One could say: it works by a lucky 'design' decision' of the LaTeX developers) – user31729 Mar 22 '18 at 12:22
  • 1
    \pageref isn't expandable, that's the reason – user31729 Mar 22 '18 at 12:33
1

The page label reference value can be extracted with \crtrefpage from the crossreftoolspackage as well, which is an expandable command. There's no need to use expl3 here. 

\documentclass{article}
\usepackage{lipsum}
\usepackage{multicol}
\usepackage{hyperref}

\usepackage{crossreftools}

\makeatletter

\newcounter{mycounter}

\newcommand{\mycommand}{%
  \refstepcounter{mycounter}%
  \label{myitems@\themycounter}
  \typeout{Processing Item No \themycounter}
  \typeout{Label Info From Aux File Is 
    \csname r@myitems@\themycounter\endcsname}
  \typeout{Pageref From Aux File Is \crtrefpage{myitems@\themycounter}}
}

\makeatother

\begin{document}

\begin{multicols}{2}[\section{Section}]
  \mycommand
  \lipsum[1-10]
  \mycommand
  \lipsum[1-5]
  \mycommand
\end{multicols}

\end{document}
Improve this answer
  • I removed the latex3 commands from my MEW (it was a relict from a more complicated source). However, I found that just using \getpagerefnumber instead of \pageref solves my problem (see my own answer). Is there any reason to prefer your solution (which involves an extra package after all)? – LaTechneuse Mar 22 '18 at 12:02
  • @LaTechneuse: No, there's no advantage, it's just another solution – user31729 Mar 22 '18 at 12:06
0

All right, I see that there is a simple solution by using \getpagerefnumber{myitems@\themycounter}} instead of \pageref{myitems@\themycounter}}.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.