RosettaCodeData/Task/Fibonacci-sequence/Lasso/fibonacci-sequence.lasso

define fibonacci(n::integer) => {

   #n < 1 ? return false

   local(
      swap  = 0,
      n1    = 0,
      n2    = 1
   )

   loop(#n) => {
        #swap = #n1 + #n2;
        #n2 = #n1;
        #n1 = #swap;
   }
   return #n1

}

fibonacci(0) //->output false
fibonacci(1) //->output 1
fibonacci(2) //->output 1
fibonacci(3) //->output 2