Repeating enumerated list items and their original number

Question

Sometimes enumerated lists are used to list example sentences which are referred to from the text by their numbers in the list. But as such references are made from far away pages it might be irritating to the reader to have to turn back all those pages to get to the referred sentence. To avoid this one may want to repeat some list items along with their original number. An rough example of how this would look is the following:

 1. Example 1
 2. Example 2

Some text with references to 1. and 2.

 3. Example 3.

Some text across several pages.

 1. Example 1

Some text with references to 1.

The problem in achieving this is to get the repeated list item with its original number without interrupting the sequence of numbers for list items occurring before and after the place where the repeated list item is placed.

Here is an example of a failure to achieve this:

\documentclass{article}

\usepackage{enumitem}

\newcommand\extwo{Example 2}

\begin{document}    
\begin{enumerate}
\item Example 1
\item \extwo
\end{enumerate}
Text
\begin{enumerate}[resume]
\item Example 3
\end{enumerate}
Text
\begin{enumerate}[start=2]
\item \extwo% Example 2 repeated with its original number, i.e. "1."
\end{enumerate}
Text
\begin{enumerate}[resume]
\item Example 4% Is listed as "3." when I want it be listed as "4."
\end{enumerate}
\end{document}

There are mainly two problems with this example:

1. Example 4 is supposed to resume the list number sequence after Example 3 but it is not.
2. It is fragile. If the order of Example 1 and Example 2 were to be changed then the third list has to have its argument changed to [start=1].

Can this example be fixed to achieve what I want or is there some more appropriate way to achieve it?

Answer 1

Personally I don't like this kind of repetition, although it is used by some. I think it's preferable to repeat the example with a new number. But independent of this opinion, the effect is easily achieved with both the gb4e package and the linguex package.

gb4e

It provides an \exr{<label>} command, which formats the example based on reference to a label.

\documentclass{article}

\usepackage{gb4e}

\newcommand\extwo{Example 2}

\begin{document}    
\begin{exe}
\ex Example 1
\ex \extwo \label{ex2}
\end{exe}
Text
\begin{exe}
\ex Example 3
\end{exe}
Text
\begin{exe}
\exr{ex2} \extwo% Example 2 repeated with its original number, i.e. "1."
\end{exe}
Text
\begin{exe}
\item Example 4% Is listed as "3." when I want it be listed as "4."
\end{exe}
\end{document}

linguex

It allows its \ex. command to have an following optional argument to set the label. This argument can contain a \ref{} command.

\documentclass{article}
\usepackage{linguex}
\newcommand\extwo{Example 2}
\begin{document}

\ex. Example 1

\ex. \extwo \label{ex2}

Text.

\ex. Example 3

Text.

\ex.[\ref{ex2}] \extwo

Text
\ex. Example 4

\end{document}