中国留学生中女性的口语一般高于男性?# Biology - 生物学
c*e
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#include
using namespace std;
class Base {
protected:
virtual void output(std::ostream& os) { os << "Base\n"; }
};
class Derived : private Base {
friend std::ostream& operator<};
std::ostream& operator<d.output(os);
}
int main() {
Base b; Derived d;
std::cout << b << d;
}
For which one of the following reasons is the code above INVALID?
a) Base::output is defined for Base, but operator<< is defined for Derived.
b)
using namespace std;
class Base {
protected:
virtual void output(std::ostream& os) { os << "Base\n"; }
};
class Derived : private Base {
friend std::ostream& operator<};
std::ostream& operator<d.output(os);
}
int main() {
Base b; Derived d;
std::cout << b << d;
}
For which one of the following reasons is the code above INVALID?
a) Base::output is defined for Base, but operator<< is defined for Derived.
b)
