[ltbarcly3]

Yes, programming languages come and go, but I don't see how that matters. Some future historian will either have access to a working copy of xz or they will not. If they don't, and they want to implement it, having a copy of the source code is far better than anything else you could give them. Sure, future programming languages will be quite different, but humans will certainly be able to read and understand C code. If humanity has forgotten how to read C code (and lost all knowledge of it), how are they going to read this documentation you seem to prefer? Human languages come and go also..

https://en.wikipedia.org/wiki/Egyptian_hieroglyphs

https://en.wikipedia.org/wiki/Judaeo-Aragonese

https://en.wikipedia.org/wiki/Latin

Any argument you can make about historians being able to recover dead languages you can make the exact same argument for their ability to recover dead computer languages, and there is no better or more accurate specification than the actual code.

So let me add to my recommendation, in addition to a copy of the xz source code, include a plain text copy of any 'how to program in C' book, or just the wikipedia page for the C language. That is more than enough for them to construct a program that can decompress xz files, once they relearn how to read whatever long dead language the book is written in (Ancient Pre-Cataclysm Earth English for example).

[fao_]

> If humanity has forgotten how to read C code (and lost all knowledge of it), how are they going to read this documentation you seem to prefer?

Sure but are they going to remember something like, weird precedence rules (See: &), undefined behaviour, etc. Just because they want to reimplement a specific, small, program does not mean they want to relearn several languages. What you're saying could easily blow up from 'how to code C' to 'reading the GCC / Clang compiler source code to figure out how a specific UB was implemented, which the program in this specific case falls into', which I'm sure nobody wants to spend their weekend doing, implementing something like `xz` could simply be a midpoint in their destination, they don't want to spend weeks digging up COBOL. Have at least some consideration for the human element, jeez.

Documentation, specifically _mathematical_ documentation, is more fault tolerant than either psuedocode or actual code.

At any other time, I would agree with you, but where archivism is concerned, I do not.

[theamk]

Are you saying it would be easier to implement xz from mathematical documentation than from computer program? I don't think so. I tried (multiple times) to implement algorithms from "mathematical documentation" in academic papers, and it is usually very bad, there are always missing parts. If I had a choice, I'd choose ALGOL-58 over human-language description anytime.

[ltbarcly3]

>> What you're saying could easily blow up from 'how to code C' to 'reading the GCC / Clang compiler source code to figure out how a specific UB was implemented, which the program in this specific case falls into', which I'm sure nobody wants to spend their weekend doing

There will be many, many people that will gladly dig into the minutia and technical details of arcane hardware, especially when it means making progress towards filling in the historical record. This is already the case today, there is a working https://en.wikipedia.org/wiki/Colossus_computer reconstructed just because it was historically significant.

[fao_]

I think you missed the implication that I didn't state explicitly, but figured was pretty clear:

> which I'm sure nobody wants to spend their weekend doing [if their original goal was to simply reconstruct xz].