I’ve joined a local study group that’s going through The Little Schemer. I learned LISP in the early ’80s but never pursued it deeply. (I certainly used Emacs, but never fully embraced it.) My purpose now is as a refresher on recursion.
For a quick useful IDE on OS X, the Dr. Racket IDE seems to fit the bill nicely. (Racket is in the LISP family.)
To use Dr. Racket, the upper portion is an editor, and when run, provides an interactive command prompt below. (Dr. Racket will probably complain about needing a language. Simply select Racket.)
To use Dr. Racket with The Little Schemer, one will need to add the definition for atom? immediately after this opening line, then run the script to bring up the command line.
(define atom? (lambda (x) (not (list? x))))
Also, one should note that Scheme requires literals such as atom as lists to be quoted:
(list? (quote ()))
(atom? (quote abc))