def fac (f)
    function (n)
      if (equal? n 0) 1
        * n (f (- n 1))
def fib (f)
  function (n)
    cond
      (equal? n 0) 0
      (equal? n 1) 1
      else (+ (f (- n 1)) (f (- n 2)))

def Y (f)
  (function (x) (x x))
      function (y)
          f
             function (&rest args) (apply (y y) args)

assertEqual ((Y fac) 5) 120
assertEqual ((Y fib) 8) 21