I stand corrected. POSIX apparently never wanted it, but yash, the “most POSIX-compliant in the world” has allowed it as an extension. Also looks like zsh does

I stand corrected. POSIX apparently never wanted it, but yash, the “most POSIX-compliant in the world” has allowed it as an extension. Also looks like zsh does it—-does that mean bc is obsolete on Mac?