monad

var Fibonacci Monad[uint] = func() Iterator[uint] {
	a, b := uint(0), uint(1)
	return func() (uint, bool) {
		a, b = b, a+b
		return a, true
	}
}

var Natural Monad[uint] = func() Iterator[uint] {
	var n uint = 0
	return func() (uint, bool) {
		n++
		return n - 1, true
	}
}

var Prime Monad[uint] = Filter(oddNonUnit, func(n uint) bool {
	return 0 == Reduce(oddNonUnit, func(numFactors uint, m uint) (uint, bool) {
		if numFactors > 0 {
			return numFactors, false
		}
		if m*m > n {
			return numFactors, false
		}
		if m%n == 0 {
			return numFactors + 1, true
		} else {
			return numFactors, true
		}
	}, 0)
}).Insert(2)