Must take void overloading operator !

[Winsu]

I though that overloading an operator when It is a member of a class what return in a member of the class but overloading this operator ! the compiler says that It must return void...

class arithmetic{
public:
	int a;
	int b;
	bool Z;
	bool Y;
	arithmetic () {};
	arithmetic(int x,int y) : a(x),b(y){};
	arithmetic(bool x,bool y): a(true),b(false){};

.....
....
arithmetic operator!(const arithmetic& param);

[Winsu]

Resolved: It cant take an argument....