下面的程序怎样修改才没错 在v6下

#include<iostream>
#include<sstream>
using namespace std;


class Point
{
friend ostream& operator<<(ostream&,const Point&);
public:
Point(double=0.0,double=0.0);
Point(const Point&);
~Point();
Point& operator=(const Point&);
double x() const;
double y() const;
string toString() const;
protected:
double _x,_y;
};
 #include"Point1.h"


class Line
{ friend class Point;
friend ostream& operator<<(ostream&,const Line&);
public:
Line(double=1.0,double=1.0);
Line(const Point&,double=0.0);
Line(const Point&,const Point&);
Line(double,double,double);
Line(const Line&);
~Line();
Line& operator=(const Line&);
double xCoef() const;
double yCoef() const;
double cTerm() const;
string toString() const;
protected:
double _a,_b,_c;
};


#include"Line.h"

ostream& operator<<(ostream& ostr,const Point& point)
{
return ostr<<point.toString();
}


Point::Point(double x,double y):_x(x),_y(y){ }
Point::Point(const Point& p):_x(p._x),_y(p._y){ }
Point::~Point(){};
Point& Point::operator=(const Point& p)
{
_x=p._x;
_y=p._y;
return *this;
}
double Point::x() const{return _x;}
double Point::y() const{return _y;}
string Point::toString() const
{ostringstream output;
output<<"("<<_x<<","<<_y<<")";
return output.str();
}


ostream& operator<<(ostream& ostr,const Line& line)
{
return ostr<<line.toString();
}
Line::Line(double x0,double y0):_a(y0),_b(x0),_c(-x0*y0){}
Line::Line(const Point& p,double m):_a(m),_b(-1),_c(p._y-m*p._x){}
Line::Line(const Point& p,const Point& q):_a(q._y-p._y),_b(p._x-q._x),_c(q._x*p._y-p._x*q._y){}
Line::Line(double a,double b,double c):_a(a),_b(b),_c(c){}
Line::Line(const Line& l):_a(l._a),_b(l._b)_c(l._c){}
Line::~Line(){}
Line& Line::operator=(const Line& line)
{
_a=line._a;
_b=line._b;
_c=line._c;
return *this;
}
double Line::xCoef() const{return _a;}
double Line::yCoef() const{return _b;}
double Line::cTerm() const{return _c;}
string Line::toString() const
{
ostringstream out;
out<<_a<<"x+"<<_b<<"y+"<<_c<<"=0";
return out.str();
}

int main()
{
Point p1(4,1);
cout<<"p1="<<p1<<"\n";
Line line1(2,3,6);
cout<<"line1:"<<line1<<"\n";
Line line2(-2,12);
cout<<"line2:"<<line2<<"\n";
Line line3(p1,3);
cout<<"line3:"<<line3<<"\n";
Point p2(0,5);
cout<<"p2="<<p2<<"\n";
Line line4(p1,p2);
cout<<"line4:"<<line4<<"\n";
}

前面2个作为头文件 后面的是cpp文件 怎么调式有错误 该怎么修改呢？？、

感觉这代码编译也过不了才对

ostream& operator<<(ostream& ostr,const Point& point)
应该放到namespace std里

Line::Line(const Line& l):_a(l._a),_b(l._b),_c(l._c){}

public:
double _x,_y;

C/C++ code

#include<iostream>
#include<sstream>
using namespace std;


class Point
{
    friend ostream& operator<<(ostream&,const Point&);
public:
    Point(double=0.0,double=0.0);
    Point(const Point&);
    ~Point();
    Point& operator=(const Point&);
    double x() const;
    double y() const;
    string toString() const;
public:
    double _x,_y;
};


class Line
{ friend class Point;
friend ostream& operator<<(ostream&,const Line&);
public:
    Line(double=1.0,double=1.0);
    Line(const Point&,double=0.0);
    Line(const Point&,const Point&);
    Line(double,double,double);
    Line(const Line&);
    ~Line();
    Line& operator=(const Line&);
    double xCoef() const;
    double yCoef() const;
    double cTerm() const;
    string toString() const;
protected:
    double _a,_b,_c;
};

ostream& operator<<(ostream& ostr,const Point& point)
{
    return ostr<<point.toString();
}


Point::Point(double x,double y):_x(x),_y(y){ }
Point::Point(const Point& p):_x(p._x),_y(p._y){ }
Point::~Point(){};
Point& Point::operator=(const Point& p)
{
    _x=p._x;
    _y=p._y;
    return *this;
}
double Point::x() const{return _x;}
double Point::y() const{return _y;}
string Point::toString() const
{ostringstream output;
output<<"("<<_x<<","<<_y<<")";
return output.str();
}


ostream& operator<<(ostream& ostr,const Line& line)
{
    return ostr<<line.toString();
}
Line::Line(double x0,double y0):_a(y0),_b(x0),_c(-x0*y0){}
Line::Line(const Point& p,double m):_a(m),_b(-1),_c(p._y-m*p._x){}
Line::Line(const Point& p,const Point& q):_a(q._y-p._y),_b(p._x-q._x),_c(q._x*p._y-p._x*q._y){}
Line::Line(double a,double b,double c):_a(a),_b(b),_c(c){}
Line::Line(const Line& l):_a(l._a),_b(l._b),_c(l._c){}
Line::~Line(){}
Line& Line::operator=(const Line& line)
{
    _a=line._a;
    _b=line._b;
    _c=line._c;
    return *this;
}
double Line::xCoef() const{return _a;}
double Line::yCoef() const{return _b;}
double Line::cTerm() const{return _c;}
string Line::toString() const
{
    ostringstream out;
    out<<_a<<"x+"<<_b<<"y+"<<_c<<"=0";
    return out.str();
}

int main()
{
    Point p1(4,1);
    cout<<"p1="<<p1<<"\n";
    Line line1(2,3,6);
    cout<<"line1:"<<line1<<"\n";
    Line line2(-2,12);
    cout<<"line2:"<<line2<<"\n";
    Line line3(p1,3);
    cout<<"line3:"<<line3<<"\n";
    Point p2(0,5);
    cout<<"p2="<<p2<<"\n";
    Line line4(p1,p2);
    cout<<"line4:"<<line4<<"\n";

    return 0;
}

using namespace std;这个去掉，需要所有用到std的都加上std，比如std::cin

F:\study\C++编程\Line2.cpp(95) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(97) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(99) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(101) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(103) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(105) : error C2593: 'operator <<' is ambiguous会出现这个错误 我的是vc6.0
问题在于主函数里

F:\study\C++编程\Line2.cpp(95) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(97) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(99) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(101) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(103) : error C2593: 'operator <<' is ambiguous
F:\study\C++编程\Line2.cpp(105) : error C2593: 'operator <<' is ambiguous会出现这个错误 我的是vc6.0
问题在于主函数里