Let's look at two versions of this function:
(defun fib2 (n) public int fib2(int n) {
(if (< n 2) if (n < 2)
n return n;
else return
(+ (fib2 (- n 2)) fib2(n - 2) +
(fib2 (- n 1)) ) ) ) fib2(n - 1); }
(defun fib1 (n) (fib1b 0 1 n))
(defun fib1b (lo hi steps)
(if (<= steps 0)
lo
(fib1b hi (+ lo hi) (- steps 1)) ) )
public int fib1(int n) { return fib1b(0, 1, n); }
public int fib1b(int lo, int hi, int steps) {
if (steps <= 0)
return lo;
else return fib1b(hi, (lo + hi), steps - 1); }