include ..\Utilitys.tlhy
:fib %f !f
%fr
[ %n !n
$n 2 <
( [$n]
[$n 1 - $fr eval $n 2 - $fr eval +] )
if
] !fr
$f 0 <
( ["Error: number is negative"]
[$f true $fr if] )
;
25 fib ?
msec ?
"End " input