--- /dev/null
+/* fibonacci */
+
+/* F_0 = 0 */
+/* F_1 = 1 */
+/* F_n = F_{n-1} + F_{n-2} */
+
+method fib(x)
+ var a := 0;
+ var b := 1;
+ if x < 2 then return x; end;
+ while not (x < 2)
+ do
+ var A := a;
+ a := b;
+ b := b-(0-A);
+ x := x-1;
+ end;
+ return b;
+end;