The co_yield Keyword

Thanks to co_yield you can implement a generator generating an infinite data stream from which you can successively query values. The return type of the generator

generator<int> generatorForNumbers(int begin, int inc= 1)

is generator<int>, where generator internally holds a special promise p such that a call co_yield i is equivalent to a call co_await p.yield_value(i). Statement co_yield i can be called an arbitrary number of times. Immediately after each call, the execution of the coroutine is suspended.

An infinite data stream

...