/* 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; var B := b; a := B; b := A-(0-B); x := x-1; end; return b; end;