优质解答

在Windows XP+VC++6.0下编译通过并正常运行

我的测试程序是用默认参数值初始化的

当然,你可以改为:

Point P(2,3);

Line L(1,2,3);

其它的都不变

懂了么?

#include

#include

using namespace std;

class Line;//声明类Line,因为Point类中声明友元函数friend dist(Point P,Line L)用到该类

class Point

{

private:

double x;

double y;

public:

Point(double xx=0,double yy=0)

{

x=xx;

y=xx;

}

friend double dist(Point P,Line L);

};

class Line

{

private:

double a;

double b;

double c;

public:

Line(double aa=1,double bb=1,double cc=1)

{

a=aa;

b=bb;

c=cc;

}

friend double dist(Point P,Line L);

};

double dist(Point P,Line L)

{

double s;

s=(L.a*P.x+L.b*P.y+L.c)/sqrt(L.a*L.a+L.b*L.b);

if(s>0)

return s;

else

return -s;

}

int main()

{

Point P;//这相当于 Point P(0,0);

Line L;//相当于 Line L(1,1,1);

cout