RosettaCodeData/Task/Fibonacci-sequence/WDTE/fibonacci-sequence-2.wdte

let s => import 'stream';
let a => import 'arrays';

let fib n => (
   let reducer p n => [a.at p 1; + (a.at p 0) (a.at p 1)];
   s.range 1 n
   -> s.reduce [0; 1] reducer
   -> a.at 1
   ;
);