Naïve Sieve of Eratosthenes

naïve.es6

function * nullEveryNth (skipFirst, n, iterable) {
  const iterator = iterable[Symbol.iterator]();

  yield * take(skipFirst, iterator);

  while (true) {
    yield * take(n - 1, iterator);
    iterator.next();
    yield null;
  }
}

function * sieve (iterable) {
  const iterator = iterable[Symbol.iterator]();
  let n;

  do {
    const { value } = iterator.next();

    n = value;
    yield n;
  } while (n == null);

  yield * sieve(nullEveryNth(n * (n - 2), n, iterator));
}

const Primes = compact(sieve(range(2)));

// General-Purpose Lazy Operations

function * range (from = 0, to = null) {
  let number = from;
  
  if (to == null) {
    while (true) {
      yield number++
    }
  }
  else {
    while (number <= to) {
      yield number++;
    }
  }
}

function * take (numberToTake, iterable) {
  const iterator = iterable[Symbol.iterator]();

  for (let i = 0; i < numberToTake; ++i) {
    const { done, value } = iterator.next();
    if (!done) yield value;
  }
}

function * compact (list) {
  for (const element of list) {
    if (element != null) {
      yield element;
    }
  }
}