This is an implementation of Lisp in less than 1k lines of C.  This language
can't do anything other than a simple math, but might be interesting to those
who want to see how dynamic scoping, macro system, and copying GC can be
implemented in C.

To compile:

  $ cc -o minilisp minilisp.c

Examples:

  (+ 1 2)
  ;; -> 3

  (define a 3)
  (+ a a)
  ;; -> 6

  (defun double (x) (+ x x))
  (double 6)
  ;; -> 12

  '(+ 1 2)
  ;; -> (+ 1 2)

  (defmacro if-zero (x then) (list 'if (list '= x 0) then))
  (macroexpand '(if-zero x (print x)))
  ;; (quote (if-not-zero x (print x)))
  (if-zero 0 42)
  ;; prints "42"