[texhax] Theorem numbering

Uwe Lueck uwe.lueck at web.de
Mon Sep 13 21:57:11 CEST 2010

This may be one of the rather serious contributions of mine:

Barbara Beeton <bnb at ams.org>, 04.06.2010 15:34:59:
> stefan witzel asks for the ability to
> "re-use" a theorem with the same number
> as the original.
> re-using the theorem text is
> left as an exercise for the reader.

Actually doing the exercise:

I thought of the `extract' package (ctan.org/pkg/extract) or some 
`verbatimwrite' (ctan.org/pkg/moreverb, 
quite a few packages have similar functions)—difficult 
to learn—more easy instead (although not tested, sorry): 
Type theorem body code in an extra file, say, thm-outs.tex. 
To typeset the theorem at its "proper" place, type 
Barbara’s xrefthm is enlightening, 
yet I would prefer the following generalization 
(in the document preamble—once I desired to have this! 
e.g.: Thm. 2* an “analogue” of Thm. 2 for a different setting): 
\newtheorem*{the-var-id-thm}{Theorem \thethmid} 
To be used like this: 

I prepared the previous as HTML (looks finer) at


(you may find an older version with some mistakes).



>    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
>			--------------------
>  \def\thexref{\ref{#1}}
>  \begin{thexrefthm}
>  \end{thexrefthm}
>\newtheorem*{thexrefthm}{Theorem \thexref}
>In this section we have two theorems.
>The first is an ordinary theorem.
>The other is a duplicate of a theorem in a later
>section, with its original number.
>Here we have a different ``forward referenced'' theorem.
>This theorem also has a number from a later section.
>In this section we have three theorems.
>The first is an ordinary theorem.
>But this one will be referenced earlier in the
>paper with the theorem number from here.
>And this one will also be referenced earlier
>with its own number.

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