Restate statements before declaration

TLDR

How to throw all dirty but necessary "lemmas/proofs" in the appendix, and restate them in the main text?

I had a few attempts, and it seemed that my requests are weird.. so I would explain a bit before I ask the question.

I'm writing a mathematical paper. I view writing math arguments as writing codes: statements are "functions" and proofs are the flesh. For completeness, I want to include as much proof as I want. However, since the structure of argument is not linear, doing so must by large decreases the readability. Therefore, I want to hide the dirty things in the appendix, and quote the def/thm/proof in my main text.

Ideally, a pseudo tex code should look as follows.

Section 1#call{main-theorem}  % nothing input here.#endcall..Section 10..Appendix#theorem[callable]{main-theorem}2-1=1.#end-theorem

To achieve this, @Bernard has pointed to thmtools for me in [1]. To achieve what I really want, I got an error, but since it's not the main topic there, I make a new question here.

Minimal example

Below is a (almost) working minimal example.

\documentclass{article}\usepackage{thmtools, thm-restate}\declaretheorem{theorem}\begin{document}%\firsteuclid*%%% Uncommenting the above causes an error:%%% > ! Undefined control sequence.%%% > l.7 \firsteuclid\begin{restatable}[Euclid]{theorem}{firsteuclid}\label{thm:euclid}$$1+1 = 2.$$\end{restatable}\firsteuclid* % This, however, works fine.\end{document}

It compiles correctly. However, I hope that I can first call \firsteuclid* before it has been stated. An attempt fails. You can replicate that by uncommenting the commented line.

One work-around, of course, is to accept its limit, and declare statements anyway as in [2]. But I also hope that the dirty codes can all be grouped together in the source file. It will make my life much easier in the future, when I want to use them in my next paper.. again, the analogy holds: you write good codes, and use them again and again.

Question

How to throw all dirty but necessary "codes" in the appendix, and restate them in the main text?

Reference

• [1] Quoting from the same document?

• [2] using a restatable before it is stated

• [3] Also related.. my another attempt Delay presenting a section