Compile time safe nullable/optional

nullable.cpp

#include <cstdio>


template <typename T>
class Nullable
{
public:
	Nullable(T* _val) : value(_val) {}
	void operator=(const Nullable<T>& rhs) { value = rhs.value; }

	template <typename F>
	void is(F f)
	{
		if (value) f(*value);
	}

private:
	T* value;
};


int main()
{
	int x = 4;
	Nullable<int> nullable_m(&x);
	Nullable<int> nullable_n(nullptr);

	nullable_m.is([&](auto val) {
		printf("%d == %d", val, x);
	});

	nullable_n.is([](auto val) {
		printf("%d", val);
	});

	return 0;
}