Generators
When you need to lazily produce a sequence of values, consider using a generator function. Dart has built-in support for two kinds of generator functions:
To implement a synchronous generator function, mark the function body as sync*, and use yield statements to deliver values:
Stream<int> asynchronousNaturalsTo(int n) async* {
int k = 0;
while (k < n) yield k++;
}
If your generator is recursive, you can improve its performance by using yield*:
Iterable<int> naturalsDownFrom(int n) sync* {
if (n > 0) {
yield n;
yield* naturalsDownFrom(n - 1);
}
}