Function generators dart

iterable.dart

import 'dart:async';

void main() {
  var i = 20;
  final fIterable = fibonacci(Fibonacci(0, 1));
  
  fIterable.take(30).forEach((element) { print(element)});
  
  
  print('fibonacci($i) = ${fibonacci(i)}');
}

/// Computes the nth Fibonacci number.

Iterable<int> fibonacci(Fibonacci f) sync* {
    yield f.current;
    f.step();
    yield* fibo(f);
}

class Fibonacci {
  int current;
  int next;
  
  Fibonacci(this.current, this.next);
  
  factory Fibonacci.initial() {
    return Fibonacci(current: 0, next: 0);
  }
  
  void step() {
    final newNext = next + current;
    current = next;
    next = newNext;
  }
}