return c; }

ostream& operator << (ostream& output,Complex& c) { output<<\ return output; }

istream& operator >> (istream& input,Complex& c)

{ cout<<\ input>>c.real>>c.imag; return input; }

2、（17分）

class Circle:public Shape {public:

Circle(double r){radius=r;}

void set() { } {

cout<<\} cout<<\cin>>radius;

void show()

double area() {return 3.14159*radius*radius;} private: };

class Square:public Shape {public:

Square(double a){this->a=a;}

void set() { } {

cout<<\

}

cout<<\cin>>a; double radius;

void show()

double area(){return a*a;}

第 9 页

private: }; int main() { }

double a;

Circle C(5.5); C.show(); Square S(9.9); S.show();

Shape *s[]={&C,&S};

cout<<\ return 0;

第 10 页