RosettaCodeData/Task/Fibonacci-sequence/Lang/fibonacci-sequence-1.lang

fp.fib = ($n) -> {
   if($n < 2) {
      return $n
   }

   $prev = 1
   $cur = 1
   $i = 2
   while($i < $n) {
      $tmp = $cur
      $cur += $prev
      $prev = $tmp

      $i += 1
   }

   return $cur
}