And why should a cleanroom implementation be an infringement? It is not a true derivative copy. Either way, software is more akin to language or math, certainly not mechanics. We have copyrights for language, and narrow patents on applications of mathematical formulas (which in itself is debatable in its justification).

Copyrights are sufficient. You shouldn't be able to tell someone they can't use a certain software algorithm in their own program, in a different language, in a different domain. That stifles innovation.

That's what ought to be correct, but the recent decision against Facebook on VR cut directly against this view - as I understand it unavoidable mathematical and logical similarities were treated as if patented procedures. Similarity was the only thing considered. Which might force companies to the immense expense of "clean-rooming" almost everything they create to avoid problems. And that might not be a guarantee; patent law is very badly messed up by now, and Congress has refused to get involved in many issues, such as patent misuse (since the current confusion favors large companies/political campaign contributors who can best afford large legal teams and long trials.)

By prohibiting a clean-room rewrite you're skirting dangerously close to attempting to prohibit independent reinvention. That is, without hyperbole, one of the most abhorrent ideas I've ever seen.

Thankfully, software patents are unenforcable in most of the world and willfully ignored by large parts of it.