友元函数不能访问类的私有变量是怎么回事啊?    帮忙分析下原因

要全部贴出来吗?

是用命名空间,我是初学者,还在试;

头文件 friends.h
#ifndef FRIENDF
#define FRIENDF
namespace friends
{
    class Box
    {
    public:
        Box(double rlength=1.0,double rwidth=1.0,double rheight=1.0);
        ~Box();
        void Show();
        //friend double BoxSurface(const Box& other1,const Box& other2);
        friend double BoxSurface(const Box& other1);
    private:
        double length;
        double width;
        double height;
    };
}
#endif
定义文件:
friends.cpp
#include<iostream>
#include"friends.h"
using namespace std;
using namespace friends;
Box::Box(double rlength,double rwidth,double rheight):length(rlength),width(rwidth),height(rheight){}
Box::~Box()
{
    cout<<"析构"<<endl;
}
void Box::Show()
{
    cout<<"长:"<<length<<endl
        <<"宽:"<<width<<endl
        <<"高;"<<height<<endl;

}
主文件:
#include<iostream>
#include"friends.h"
using namespace std;
using namespace friends;

int main()
{
    Box aa(10.0,20.0,30.0);
    aa.Show();
    Box bb(40.0,50.0,60.0);
    bb.Show();
    cout<<"两高: "<<BoxSurface(aa)<<endl;
    return 0;
}
double BoxSurface(const Box& other1)
{
    return  other1.height+other1.width+other1.length;
}

我在线等着啊...谢谢你的帮忙呢.

还是不晓得调啊.

你调了那个程序没?  好像是说不能放问类的私有成员

呵呵,出来了呢,谢谢你啊,原来是那个友元函数没有加空间名字的.