[qiskit]

Same. Never seen that symbol in my life. I've seen ¬, ~, !, etc used for not/negation in computer science, math, logic, etc.

And some commenters said they used it to mark proof by contradiction, but why is there a need to mark it when you are showing it via proof? A canonical example of proof by contradiction is proving sqrt(2) is not rational. Never have I seen it marked with that symbol. Where would you even mark it? At the beginning with the assumption? Or at the end like QED?

[AaronFriel]

Math degree holder from Iowa, yeah, I've seen and used it many times. The symbol is used when you reach the contradictory statement. Like "1 = 2".

"By way of contradiction suppose P, then ..., thus ~P ↯. Therefore ..."

[nerdponx]

I've actually always wanted a way to mark "the contradiction" once I've obtained it. Thanks!

[phogster]

To me that reads: I throw your assumption into the GROUND!

[valtism]

I was taught it in extracurricular mathematics in Australia. We were taught that it goes at the end of a contradiction proof once the contradiction has been found. We used to write it extra large, like lightning strike. I think of it like a proof mic-drop.