RosettaCodeData/Task/Fibonacci-sequence/Falcon/fibonacci-sequence-3.falcon

function fib_tr(n)
    return fib_aux(n,0,1)
end
function fib_aux(n,a,b)
   switch n
      case 0 : return a
      default: return fib_aux(n-1,a+b,a)
   end
end