RosettaCodeData/Task/Fibonacci-sequence/XLISP/fibonacci-sequence-3.l

(defun fibonacci (x)
    (defun fib (a b n)
        (if (= n 2)
            b
            (fib b (+ a b) (- n 1)) ) )
    (if (< x 2)
        x
        (fib 1 1 x) ) )