RosettaCodeData/Task/Fibonacci-sequence/SkookumScript/fibonacci-sequence-4.skookum

// Assuming code is in Integer.fibonacci() method
() Integer
  [
  if this < 2
    [this]
  else
    [
    !prev: 1
    !next: 1
    2.to_pre this
      [
      !sum :  prev + next
      prev := next
      next := sum
      ]

    next
    ]
  ]