What kind of sadist creates a language based on that?HerbieLots of stack-machine languages are based on Reverse Polish Notation, including Forth, MSIL, HP's RPN. But there is nothing reverse about Lisp.@Proton2: before IDEs started providing substantial help with that, it was common to use a final square bracket that closed any open parenthesis left.(cons a (cons b (cons (c nil)]Slightly more dan