Strictly speaking, there's no reason anyone "needs" generator functions. Instead of pausing the function execution at each `yield` statement, you can just write a regular (non-generator) function that returns a struct including all the local variables used in the function, and repeatedly call the function with the returned struct as the first argument (or `reduce`). Admittedly this is just writing the exact mechanism of yield in a different way just to avoid using `yield`, but that's the point, it's not necessary to have it built in to the language.