这个小程序是怎么会事？

[熊猫过隙]

#include <iostream.h> 


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, float)
{
	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;
	p.setPoint(8.5,6.8);
	cout << "p(new):" << p << endl;


	char response;
	cin >> response;

return 0; 
}

在vc++6.0中的编译错误提示如下：
--------------------Configuration: Cpp1 - Win32 Debug--------------------
Compiling...
Cpp1.cpp
c:\code\cpp1.cpp(26) : error C2065: 'a' : undeclared identifier
c:\code\cpp1.cpp(26) : warning C4244: '=' : conversion from 'int' to 'float', possible loss of data
c:\code\cpp1.cpp(27) : error C2065: 'b' : undeclared identifier
c:\code\cpp1.cpp(27) : warning C4244: '=' : conversion from 'int' to 'float', possible loss of data
c:\code\cpp1.cpp(40) : warning C4305: 'argument' : truncation from 'const double' to 'float'
c:\code\cpp1.cpp(42) : warning C4305: 'argument' : truncation from 'const double' to 'float'
Error executing cl.exe.

Cpp1.exe - 2 error(s), 4 warning(s)


这个程序怎么调试。谢谢

[coverallwangp]

#include <iostream.h> 


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)//修改
{
    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;
    p.setPoint(8.5,6.8);
    cout << "p(new):" << p << endl;
	
	
    char response;
    cin >> response;
	
	return 0; 
}

[wangdeqie]

void Point::setPoint(float a, float b)
{
    x = a;
    y = b;
}

[woaiyu_liang]

出错处见下面程序中的注释处：
#include <iostream.h>


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, float)//函数定义时需要给出形参名，改为void Point::setPoint(float a, float b)[/color]
{
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);//3.5与6.4皆为double型，而p函数的形参为float型，因此会出现类型不匹配的警告
cout << "x=" << p.getX() << ",y=" << p.getY() << endl;
p.setPoint(8.5,6.8);
cout << "p(new):" << p << endl;


char response;
cin >> response;

return 0;
}

[sealrose]

void Point::setPoint(float a, float b)
{
x = a;
y = b;
}



int main()
{
Point p(3.5,6.4); //改为:Point p(3.5f,6.4f); 试下
cout << "x=" << p.getX() << ",y=" << p.getY() << endl;
p.setPoint(8.5,6.8);
cout << "p(new):" << p << endl;


char response;
cin >> response;

return 0;
}