[bediger4000]

That's a good question, one I thought of, but have put off grappling with.

Based on what LLMs have given me for answers so far, I'd look harder for the human-written source of the nroff code. I have written what I believe to be the only quine in the GPP macro processing language, LLMs only refer me to my code if I ask for a GPP quine. Google, Meta, OpenAI really have strip mined the entire web.

If I genuinely thought anything creative or new appeared, I'd probably be at a loss as well.

[nickdrozd]

I gave a few attempts with ChatGPT and DeepSeek. Neither of them could get it right. So this goalpost can remain in place for the time being.

(I am assuming that the task is actually possible to accomplish. If it isn't possible, then it isn't a very good goalpost!)

[bediger4000]

It should be possible. nroff macro language has looping, string interpolation, functions and if/then/else. That macro language should be turing complete. People have written file-infecting virus malware with it, I believe, which indicate that a quine should be possible. I personally have made several attempts at an nroff quine over the years with no success.

If it's not possible, I'd love to see an explanation, so that task can quite weighing on me.

[nickdrozd]

Here is an attempt:

  .de Q
  .nf
  .na
  .pso awk 'BEGIN{bs=sprintf("%c",92); pre=bs"&"} {out=pre; for(i=1;i<=length($0);i++){c=substr($0,i,1); if(c==bs) out=out bs bs; else out=out c} print out}' "\n[.F]"
  .ex
  ..
  .Q

Invoke with:

  nroff -U -Tascii quine.roff | sed -Ez '$ s/\n+$//'

Possibly relies too much on awk + sed. So maybe not A+, but better than nothing.

[bediger4000]

To be completely honest, I don't think that counts. Shelling out to awk means you're not writing nroff.

It's possible to write quines in pure C or perl or m4 or python, without shelling out to another language.