non-member operator function

[Troubled646]

My question is: how can we make an operator function, which is not a member of a class, access private data members of class or do manipulations on objects of class? and why do we use such operator function?

[Bazzy]

You can make it friend

// anywhere in your class body:
friend ret_type operator op ( param_1, param_2 );

You need to have external operator when the first argument of it is not an object of the class

[Troubled646]

But it means that the friend function has to be declared 'inside' the class at least... Can't I declare and define it 'outside' the class, in main body?

[Bazzy]

No, that's because only the implementor of the class can decide which functions can access private members
( otherwise it wouldn't make sense to have them private )