RosettaCodeData/Task/Fibonacci-sequence/LFE/fibonacci-sequence-2.lfe

(defun fib
  ((n) (when (>= n 0))
    (fib n 0 1)))

(defun fib
  ((0 result _)
    result)
  ((n result next)
    (fib (- n 1) next (+ result next))))