> Its a formal logic symbol I've never seen this notation used in modern mathematical logic papers. I've even had (non-US) logic phds ask me about this notatio

> Its a formal logic symbol I've never seen this notation used in modern mathematical logic papers. I've even had (non-US) logic phds ask me about this notation. > which was also used by standardized test writers like the SAT. The SAT removed those questions because they were ineffective at assessment, not because the notation was out of favor. Yeah, standardized tests that have since phased it out were really the only place it was used. Hence anachronistic. If you didn't take the SAT during a certain period of time there's a god chance you didn't see this notation.