/**
 * const gen = fibGenerator();
 * gen.next().value; // 0
 * gen.next().value; // 1
 */
function* fibGenerator(): Generator<number, any, number> {
    let a = 0;
    let b = 1;
    let iter = 0;
    while (true) {
        if (iter < 2) {
            yield iter;
            iter++;
        } else {
            yield a + b;
            [a, b] = [b, a + b];
        }
    }
};