Int? addIf(Int? a, Int? b) {
	if (a) {
		if (b) {
			return a + b;
		}
	}
	return null;
}

Int? addUnless(Int? a, Int? b) {
	unless (a)
		return null;
	unless (b)
		return null;

	return a + b;
}

void maybe() {
	Int? result = addUnless("10".int, "20".int);
	print(result.toS);
}
