Lisp does NOT use RPN - Re: cctalk Digest, Vol 125, Issue 13

On Thu, Jan 9, 2014 at 2:55 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote: Lisp doesn't really have "operators" in the sense of Algol-ish languages; the closest analogue are the special operators which are primitive forms. But whereas '+' signifying addition is an operator in many languages, in Lisp it's (often) just a function. E.g., (apply #'+ (list 1 2 3)) yields 6 in a Lisp-2. But depending on the dialect, there are a few things that apply in an infix-ish way. Consider the '.' token in an improper list; one can sometimes think of this as an infix stand-in for a CONS call. In Common Lisp: CL-USER> '(a . (b . (c . nil))) (A B C) CL-USER> (cons 'a (cons 'b (cons 'c nil))) (A B C) CL-USER> Or in Scheme: guile> '(1 . (2 . (3 . ()))) (1 2 3) guile> In Common Lisp, the LOOP macro defines a language with lots of infix operators: CL-USER> (loop for (k . v) in '((1 . a) (2 . b) (3 . c)) do (format t "~A maps to ~A~%" k v)) 1 maps to A 2 maps to B 3 maps to C NIL CL-USER> Etc. Further, if you *really* wanted to in Common Lisp, you could change the read tables and redefine the syntax to essentially anything you wanted, including an infix language. :-) So while Lisp is *mostly* written using prefix notation, there are escape hatches. - Dan C.