如下C++无法运行，百思不得其解，和书上一个不差

#include <iostream>
using namespace std; //此处未写
class Point
{public:
Point(float x=0,float y=0);
void setPoint(float,float);
float getX() const {return x;}
float getY() const {return y;}
friend ostream & operator<<(ostream &,const Point &);
protected:
float x,y;
};
Point::Point(float a,float b)
{x=a;y=b;}
void Point::setPoint(float a,float b)
{x=a;y=b;}
ostream & operator<<(ostream &output,const Point &p)
{output<<"["<<p.x<<","<<p.y<<"]"<<endl;
return output;
}
int main()
{Point p(3.5,6.4);
cout<<"x="<<p.getX()<<" y="<<p.getY()<<endl;//区分" "和' '
p.setPoint(8.5,6.8);
cout<<"p(new):"<<p<<endl;
system("pause");//如果在windows下，加上此行
return 0;//虽main函数可以没有返回值就结束，但建议还是加上此语句