%% LaTeX package crossreftools - version 0.5 (2018/02/23 -- 13:46:13)
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%% Copyright (c) 2017 -- 2018 by Dr. Christian Hupfer <typography dot with dot latex at gmail dot com>
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\documentclass{book}



\usepackage{hyperref}
\usepackage[user]{zref}
\usepackage{cleveref}

\usepackage{crossreftools}


\setlength{\parindent}{0em}

\def\labeltoshow{foochapterlabel}

\def\equationlabeltoshow{fooequationlabel}


\crtlistoflabelsstructurelevel{section}
\begin{document}

\tableofcontents

\crtlistoflabels*

\clearpage

\chapter{Some easy usages of crossreftools}
%\setcounter{chapter}{16}% Just for checking

Let us refer the usual way: \Cref{\labeltoshow}

\edef\foocntr{\crtcrefcounter{\labeltoshow}}  

The counter for \fbox{\labeltoshow} is \foocntr\ or \crtcrefcounter{\labeltoshow}. It is used on page \crtcrefpage{\labeltoshow}. The value for the misspelled label name is \crtcrefnumber{labeltoshowstuff}, whereas the correct value is \crtcrefnumber{\labeltoshow}. 



The result is \fbox{\crtcrefresult{\labeltoshow}}

\edef\labeltoshowname{\crtcrefname{chapter}}

\section{Extracting usual reference information}

Extracting content with  \verb!\crtextractref!
  \begin{itemize}
  \item reference:   \crtextractcref{reference}{\labeltoshow}
  \item page:   \crtextractcref{page}{\labeltoshow}
\end{itemize}

If the \fbox{hyperref} package is loaded, further properties are retrievable:

\begin{itemize}
  \item name:   \crtextractref{name}{\labeltoshow}
  \item hyperanchor: \crtextractref{anchor}{\labeltoshow}
  \item unused: \crtextractref{unused}{\labeltoshow}
  \end{itemize}
  
The 5th (and usually empty) label property introduced by hyperref is unused as of version v6.85a of that package -- \crtextractref{unused}{labelname} will return nothing here, i.e. the expansion is empty.  


This works only if there is usual hyper anchor for the counter: \crtrefcounter{fooequationlabel}. 

\section{Extracting the cleveref names}

\begin{itemize}
  
\item The lower case cross reference name for \fbox{\equationlabeltoshow} is \crtcrefnamebylabel{\equationlabeltoshow}, this time using \verb!\crtcrefnamebylabel!; the upper case name is \crtCrefnamebylabel{\equationlabeltoshow}.
\item  Extracting content with  \verb!\crtextractcref!
  \begin{itemize}
  \item counter: \crtextractcref{counter}{\labeltoshow}
  \item number: \crtextractcref{number}{\labeltoshow}
  \item result: \crtextractcref{result}{\labeltoshow}
  \item reference:   \crtextractcref{reference}{\labeltoshow}
  \item page:   \crtextractcref{page}{\labeltoshow}
  \end{itemize}
\end{itemize}

The macro \verb!\crtextractcref! is expandable!\edef\counterof{\crtextractcref{counter}{\labeltoshow}} Using the stored value for counter: \counterof!


See \crthyperCref{fooequationlabel} and \cref{pythagoreantheorem}.



\chapter{Placing more generic labels}

\clearpage
\crtcrossreflabel[Let us place a label without a counter]{Let us plant a label not being connected to a counter:}[somelabel]



\clearpage

See \ref{somelabel} or \nameref{somelabel} on \cpageref{somelabel}


\chapter{This is foo}\label{foochapterlabel}

\setcounter{section}{5}
\section{Foo}\label{foosectionlabel} \zlabel{foosectionlabel}

\begin{equation}
  E=mc^{2}\label{firstequationlabel}
\end{equation}

\begin{equation}
  E=mc^{2}\label{fooequationlabel}
\end{equation}


\clearpage

\section{Another foo bar section}
\begin{equation}
  a^{2} + b^{2}=c^{2}\label[section]{pythagoreantheorem}% Explicitly use a wrong counter type here for testing
\end{equation}


\chapter{Checking for label existence}

\crtifdefinedlabel{firstfooequationlabel}{%
  Yes, that label exists%
}{
  No, that label does not exist%
}

\crtcrefifdefinedlabel{fooequationlabel}{%
  Yes, that cleveref label exists%
}{
  No, that cleveref label does not exist%
}




\end{document}