Repeat content of environment

Question

Sometimes you want proofs of theorems to appear in an appendix. The appendix must then

1. include the theorem claim exactly as it was stated in the main body of the paper
2. add a proof to it.

It would be nice to be able to include the theorem in the appendix without having to copy it verbatim (also because if I change it in the main body of the paper, I have to change it in the appendix as well).

Is there a clean way to achieve this in LaTeX? Note that theorem claims may include numbered objects (such as equations) and these numbers must not change in the repetition.

Answer 1

Load the restatable package (comes with thmtools) and use the restatable environment, like this (adapted from the documentation of thmtools):

\begin{restatable}[Euclid]{theorem}{firsteuclid}
\label{thm:euclid}%
For every prime $p$, there is a prime $p’>p$.
In particular, the list of primes,
\begin{equation}\label{eq:1}
2,3,45,7,\dots
\end{equation}
is infinite.
\end{restatable}

... Some text ...
.................

\firsteuclid*

Explanation: you make your theorem environment and its optional argument as arguments of the restatable environment, adding a name for the command which will be used to restate the theorem (with the same number) – here it is firsteuclid. The star in the command says the reference should be to the original theorem, not the restated.