A: Mostly can be overloaded. The only C operators which can't be are. and?: (and sizeof, that is technically an operator). C++ adds a few of its own operators, mostly which can be overloaded except :: and .*.

Here's an instance of the subscript operator (it returns a reference). Primary without operator overloading:

class Array {

public:

int& elem(unsigned i) { if (i > 99) error(); return data[i]; }

private:

int data[100];

};

int main()

{

Array a; a.elem(10) = 42; a.elem(12) += a.elem(13);

...

}

Now the similar logic is presented along with operator overloading:

class Array {

public:

int& operator[] (unsigned i) { if (i > 99) error(); return data[i]; }

private:

int data[100];

};

int main()

{

Array a; a[10] = 42; a[12] += a[13];

...

}