Perl is a great language for writing obfuscated code. All those strange symbols, and default variables, and odd language "features" hardly anyone knows about, make it an easy medium for writing obfuscated code.

I would think that Lisp, while not having such a diverse syntax, would also make a good language for writing obfuscated code. Macros, continuations, and the mini-languages like format and loop make code confusing enough for beginners that I would think someone actually trying to obfuscate code could build something truly impressive with them. But I don't know of any examples of obfuscated Lisp out in the wild.

So here is my first attempt at writing some obfuscated Arc. I figure that to achieve maximum confusion, I should take advantage of macros and continuations, possibly combining the two. One idea in particular that has intrigued me is calling continuations back to macro expansion time. I had doubts that it would actually work, but I tried it and it did...

I'm not completely sure how to take advantage of that, but one idea that I've had is to redefine a function every time it gets called. Here is the code:

  (mac mdef (name args . body)
    (let cc nil
      (let rc (ccc (fn (c) (= cc c) nil))
        (w/uniq (mc fc return)
          `(with (,mc ,cc ,fc ,rc)
             (def ,name ,args
               (let ,return (do ,@body)
                 (ccc (fn (c) (,mc (fn () (c ,return)))))))
             (if ,fc (,fc)))))))

  (let n 0
    (mac n++ ()
      (++ n)))

  (mdef mutate ()
    (prn (n++)))
  
  (mutate)
  (mutate)
  (mutate)