# [texhax] Theorem numbering

Uwe Lueck uwe.lueck at web.de
Fri Dec 3 17:12:58 CET 2010

I just have rediscovered

http://ctan.org/pkg/thmtools

the description of which indicates that it helps with these matters.

Cheers,

Uwe.

-----Ursprüngliche Nachricht-----
Von: "Barbara Beeton" <bnb at ams.org>
Gesendet: 04.06.2010 15:34:59
Betreff: Re: [texhax] Theorem numbering

>stefan witzel asks for the ability to
>"re-use" a theorem with the same number
>as the original.
>
>    I'm using the amsthm-Package and number my theorem within sections, i.e.
>
>    \newtheorem{thm}{Theorem}[section]
>
>    Now I would like to quote a theorem from the end of the paper in the
>    introduction with its original number (which is 9.1 in my case).
>    Of course I could do so by manually setting the counters:
>
>    \setcounter{section}{9}
>    \setcounter{thm}{0}
>    \begin{thm}
>    ...
>    \end{thm}
>    \setcounter{section}{1}
>    \setcounter{thm}{0}
>
>    but this destroys the idea of automatic numbering, because if my
>    theorem becomes Theorem 9.2 because it is preceded by Lemma 9.1, it
>    has the wrong number in the introduction.
>    When I once had the problem of quoting a theorem *after* it had been
>    stated, I used the following makros the save and recover the counters:
>
>    [...]
>
>    But how can I can obtain the number before the actual statement (using
>    the \label)? I imagine there should exist solutions to this, but I did
>    not find them on the web (and I don't know enough about
>    makro-programming, to extract the necessary information from the
>    \label-data myself). Many thanks in advance!
>
>the test file attached below uses \label
>to identify the theorem number, and also
>allows for multiple "re-used" theorem
>numbers.  re-using the theorem text is
>left as an exercise for the reader.
>						-- bb
>
>			--------------------
>
>\documentclass{article}
>\usepackage{amsthm}
>
>\newtheorem{thm}{Theorem}[section]
>\newenvironment{xrefthm}[1]{%
>  \def\thexref{\ref{#1}}
>  \begin{thexrefthm}
>}{%
>  \end{thexrefthm}
>}
>\newtheorem*{thexrefthm}{Theorem \thexref}
>
>\begin{document}
>
>\section{Introduction}
>In this section we have two theorems.
>
>\begin{thm}
>The first is an ordinary theorem.
>\end{thm}
>
>\begin{xrefthm}{laterthm}
>The other is a duplicate of a theorem in a later
>section, with its original number.
>\end{xrefthm}
>
>\section{Next}
>Here we have a different forward referenced'' theorem.
>
>\begin{xrefthm}{another}
>This theorem also has a number from a later section.
>\end{xrefthm}
>
>\setcounter{section}{8}
>\section{Ninth}
>
>In this section we have three theorems.
>
>\begin{thm}
>The first is an ordinary theorem.
>\end{thm}
>
>\begin{thm}\label{laterthm}
>But this one will be referenced earlier in the
>paper with the theorem number from here.
>\end{thm}
>
>\begin{thm}\label{another}
>And this one will also be referenced earlier
>with its own number.
>\end{thm}
>
>\end{document}
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