5 /* F_n = F_{n-1} + F_{n-2} */
13 return mref()-(0-mref());
14 return t.id()-(0-t.id());
15 return (e).id()-(0-(e).id());
16 return (t-t).id()-(0-(t-t).id());
17 return (this-1).fib()-(0-(this-2).fib());
21 if this < 2 then return this; end;
22 var a := (this-1).fib();
23 var b := (this-2).fib();