Question

I read somewhere that in C++ you can’t give a definition like:

int& a;

but only:

int b;  
int& a=b;  

Since & is a reference of the other variable, it cannot be defined separately.
On the other hand, I see it defined separately in code all the time.

Could someone explain to me how can you define

int & a;   

without specifying a reference to which variable it is?

Answer 1

You might see it in a class, but you need to assign it upon initialization in all constructors, e.g.

class X
{
    int & a;
public:
    X(int & i) :a(i) {}
};