Comment by Jtsummers

A nit, but:

> Strictly speaking, a programming language doesn't really need comments. "But Lisp has them, and puts them in double quotes."

Lisp has comments, but they aren't generally contained in double quotes, you've tossed a lot of strings into your program and called them comments. Comments are either marked with ; (comment to end of line, like //) with conventions on how many semicolons to use in particular places, or comment blocks with #| comment |# (nestable version of /* */). You can add documentation to many definitions, like functions, using strings which may be what you're thinking of but that happens inside the definition like with this:

  (defun constant (x)
    "CONSTANT returns a function which always returns X"
    (lambda (a) x))

Which is a comment, but it's unusual to use strings as comments outside of contexts like that. Also, if you're going to use strings as comments you can make them multi-line instead of doing

  "I thought about calling these car and cdr..."
  "...then decided that I'm not really THAT addicted to Lisp"

with:

  "I thought about calling these car and cdr...
  ...then decided that I'm not really THAT addicted to Lisp"

The other reason I'm posting this nit is that if anyone reads your blog/answer and tries to use comments as you've described them inside of expressions they'll be very confused about why it's behaving incorrectly. There's no reason to mislead people, this is not a comment:

  (if (= 1 2) "Should never be true" ;; that's not a comment, it's an expression
    (print "Never happens")
    (print "Always happens")) ;; your interpreter or compiler will complain about this code