Reference a section with a macro generated name

Question

I have a lot of subsections with the name "Example X.Y" in my thesis and want to use a macro which generates the names and labels for the subsections.

The goal is to be able to reference examples like in the picture below:

Using the nameref package I tried the following:

\documentclass[10pt,a4paper]{report}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{nameref}

\newcommand{\example}{\subsection{Example \arabic{section}.\arabic{subsection} }\label{ex:\arabic{section}-\arabic{subsection}}}

\begin{document}

\chapter{Simulations}
\section{Examples 1}
\example
\example
\nameref{ex:1-2} has the same solution as \nameref{ex:1-1}.

\end{document}

This however gives me the text "Example 1.2 has the same solution as Example 1.2".

I suspect that the reference is working as intended, but when substituting the subsection's name Example \arabic{section}.\arabic{subsection} is called again, resulting in only giving me the name of the current example/subsection.

Is there a way to generate subsections and labels with a macro or do I have to do it all by hand?

Welcome to TeX.SX! Please consider turning your code snippets into a fully compilable example, an MWE. I just tries to do that and failed to reproduce the undesired behaviour you see, so there must be more to it. An MWE makes it easier for us to help you, because we can see the exact same thing that you see. — moewe, May 25 '18 at 07:55
Your guess is spot on by the way, you can see in the .aux file that the counter values are not expanded in the \newlabel leading to Example \arabic{section}.\arabic{subsection} being the value of both labels. — moewe, May 25 '18 at 08:10
Very good, thank you. You need to expand the counters in the section, so nameref can pick them up properly. I can't think of a nice solution for that, unfortunately. — moewe, May 25 '18 at 08:19
What's the advantage of this system over directly writing Example~1.2 instead of \nameref{ex:1-2}, as you need to know the actual number? — egreg, May 25 '18 at 15:45

score 3 · Answer 1 · answered May 25 '18 at 16:04

It's not clear what advantage you have in using such an approach, because you need to know the number that's assigned to each particular example in order to use \ref{ex:<section>-<subsection>} and so using directly

Example~1.2

instead of \nameref{ex:1-2}` seems much easier.

You can instead use a symbolic label, which doesn't depend on the actual number that's assigned.

\documentclass[10pt,a4paper]{report}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{nameref}

\newcommand{\example}[1]{%
  \subsection{Example \ref{ex:#1}}%
  \label{ex:#1}%
}
\renewcommand\thesubsection{\arabic{section}.\arabic{subsection}}
\newcommand{\subsectionseccntformat}{\thesection.\arabic{subsection}}
\makeatletter
\renewcommand{\@seccntformat}[1]{%
  \ifcsname #1seccntformat\endcsname
    \csname #1seccntformat\endcsname
  \else
    \csname the#1\endcsname
  \fi
  \quad
}
\makeatother

\begin{document}

\chapter{Simulations}
\section{Examples 1}
\example{first}
\example{second}
\nameref{ex:first} has the same solution as \nameref{ex:second}.

\end{document}

You are right, this approach is not optimal. But since the thesis is almost finished (except for cross references and typos) I've chosen this way to save myself some typing. — Felix Auer, May 26 '18 at 07:10

score 2 · Accepted Answer · answered May 25 '18 at 13:15

You have to expand the subsection title before it is written into the aux file. You can not control writing it, so instead you can expand it before even calling subsection. Of course this means \arabic{subsection} will be the old subsection number, so you have to increase it:

\documentclass[10pt,a4paper]{report}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{nameref}
\usepackage{expl3}
\ExplSyntaxOn
\cs_new_eq:NN \expNx \exp_args:Nx
\ExplSyntaxOff

\newcommand\arabicPlusOne[1]{\number\numexpr1+\value{#1}\relax}
\newcommand\example{\expNx\subsection{Example \arabic{section}.\arabicPlusOne{subsection} }\label{ex:\arabic{section}-\arabic{subsection}}}

\begin{document}

\chapter{Simulations}
\section{Examples 1}
\example
\example
\nameref{ex:1-2} has the same solution as \nameref{ex:1-1}.

\end{document}

That seems to do the trick! Thank you very much – Felix Auer May 25 '18 at 13:27 — Felix Auer, May 25 '18 at 13:27

score 1 · Answer 3 · answered May 25 '18 at 13:45

Here is a similar solution not using LaTeX3 which uses the \begingroup\def\zzz{\endgroup ...} trick described in Explanations about \begingroup\edef\x{\endgroup. Like Marcel Krüger's solution this uses the current section counter, increases the subsection counter by one and then fully expands the argument to \section. In particular that means that the section title should be expandable (\emph for example, is out).

\documentclass[10pt,a4paper]{report}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage[T1]{fontenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{nameref}

\newcounter{faex@tempa}
\newcommand{\example}{%
  \setcounter{faex@tempa}{\value{subsection}}%
  \stepcounter{faex@tempa}%
  \begingroup
  \edef\zzz{\endgroup
    \noexpand\subsection{Example \arabic{section}.\arabic{faex@tempa}}}%
  \zzz
  \label{ex:\arabic{section}-\arabic{subsection}}}


\begin{document}
\chapter{Simulations}
\section{Examples 1}
\example
\example
\nameref{ex:1-2} has the same solution as \nameref{ex:1-1}.
\end{document}

Reference a section with a macro generated name

3 Answers3