operator overloading<< error

Question

Im trying to overload the operator<<

const ostream & operator<<(const ostream& out, const animal& rhs){
    out << rhs.a;
    return out;
}

it seems that im getting an error because im return a const and also because the first argument is const refrence to an ostream object.

cout << objectOfAnimal1 << objectOfAnimal2 ;

it work just fine if I change the the return type and the operator signature to this one:

ostream & operator<<(ostream& out, const animal& rhs)

Answer 1

You need to have:

ostream & operator<<(ostream& out, const animal& rhs)

In your code You are trying to modify a const ostream object, and so you get the errors.
It should not be const.

Answer 2

ostream & operator<<(ostream& out, const animal& rhs){
out << rhs.a;
return out;
}

You've already explained what is probable reason of problem and you really didn't try it out?