26 Ranges library [ranges]

26.8 Range generators [coro.generator]

26.8.1 Overview [coroutine.generator.overview]

Class template generator presents a view of the elements yielded by the evaluation of a coroutine.
A generator generates a sequence of elements by repeatedly resuming the coroutine from which it was returned.
Elements of the sequence are produced by the coroutine each time a co_yield statement is evaluated.
When the co_yield statement is of the form co_yield elements_of(r), each element of the range r is successively produced as an element of the sequence.
[Example 1: generator<int> ints(int start = 0) { while (true) co_yield start++; } void f() { for (auto i : ints() | views::take(3)) cout << i << ' '; // prints 0 1 2 } — end example]