新手遇到的很奇怪的问题！！！大侠进来吧

[yj19888239]

一开始出现的问题是编译过不了

代码如下：#include <iostream>
using namespace std;

class DayOfYear
{
public:
friend bool equal(DayOfYear date1, DayOfYear date2);

DayOfYear(int the_month, int the_day);
DayOfYear(){}

void input();
void output();

int get_month();
int get_day();

private:
void check_date();
int month;
int day;
};

int main()
{
DayOfYear today,yj_birthday(8,23);
cout<<"enter today's date\n";
today.input();
cout<<"yj's birthday is";
yj_birthday.output();

if(equal(today,yj_birthday))
cout<<"happy birthday yangjie!\n";
else
cout<<"happy unbirthday yangjie!\n";

return 0;
}

bool equal(DayOfYear date1, DayOfYear date2)
{

return(date1.month==date2.month&&date1.day==date2.day);

}

DayOfYear::DayOfYear(int the_month, int the_day)
{
month=the_month;
day=the_day;
check_date();
}

int DayOfYear::get_month()
{
return month;
}

int DayOfYear::get_day()
{
return day;
}

void DayOfYear::input()
{
cout<<"enter the month as a number:";
cin>>month;
cout<<"enter the day of the month:";
cin>>day;
}

void DayOfYear::output()
{
cout<<"month="<<month
<<",day="<<day<<endl;
}

void DayOfYear::check_date()
{
if((month<1)|(month>12)|(day<1)|(day>31))
{
cout<<"Illegal date. aborting program.\n";
exit(1);
}
}

出错如下：
--------------------Configuration: 11_2 - Win32 Debug--------------------
Compiling...
11_2.cpp
C:\Documents and Settings\Administrator\桌面\VC精装版\VC精装版\MyProjects\11_2\11_2.cpp(43) : error C2248: 'month' : cannot access private member declared in class 'DayOfYear'
C:\Documents and Settings\Administrator\桌面\VC精装版\VC精装版\MyProjects\11_2\11_2.cpp(20) : see declaration of 'month'
C:\Documents and Settings\Administrator\桌面\VC精装版\VC精装版\MyProjects\11_2\11_2.cpp(43) : error C2248: 'month' : cannot access private member declared in class 'DayOfYear'
C:\Documents and Settings\Administrator\桌面\VC精装版\VC精装版\MyProjects\11_2\11_2.cpp(20) : see declaration of 'month'
C:\Documents and Settings\Administrator\桌面\VC精装版\VC精装版\MyProjects\11_2\11_2.cpp(43) : error C2248: 'day' : cannot access private member declared in class 'DayOfYear'
C:\Documents and Settings\Administrator\桌面\VC精装版\VC精装版\MyProjects\11_2\11_2.cpp(21) : see declaration of 'day'
C:\Documents and Settings\Administrator\桌面\VC精装版\VC精装版\MyProjects\11_2\11_2.cpp(43) : error C2248: 'day' : cannot access private member declared in class 'DayOfYear'
C:\Documents and Settings\Administrator\桌面\VC精装版\VC精装版\MyProjects\11_2\11_2.cpp(21) : see declaration of 'day'
执行 cl.exe 时出错.

11_2.obj - 1 error(s), 0 warning(s)


然后有人说要把友元函数的声明放到了里面去，我改了过后编译没问题但是连接出错

代码如下：
#include <iostream>
using namespace std;

class DayOfYear
{
public:
friend bool equal(DayOfYear date1, DayOfYear date2);

DayOfYear(int the_month, int the_day);
DayOfYear(){}

void input();
void output();

int get_month();
int get_day();

private:
void check_date();
int month;
int day;

bool equal(DayOfYear date1, DayOfYear date2)
{

return(date1.month==date2.month&&date1.day==date2.day);

}
};
省略了的同上

出错问题：
--------------------Configuration: 11_2 - Win32 Debug--------------------
Linking...
11_2.obj : error LNK2001: unresolved external symbol "bool __cdecl equal(class DayOfYear,class DayOfYear)" (?equal@@YA_NVDayOfYear@@0@Z)
Debug/11_2.exe : fatal error LNK1120: 1 unresolved externals
执行 link.exe 时出错.

11_2.exe - 1 error(s), 0 warning(s)



然后又听高手说后把private改成public编译和连接都没问题了
但是没用到private的话不就没意义了吗？
我就是想学习运用一下友元函数和private

代码如下：
#include <iostream>
using namespace std;

class DayOfYear
{
public:
friend bool equal(DayOfYear date1, DayOfYear date2);

DayOfYear(int the_month, int the_day);
DayOfYear(){}

void input();
void output();

int get_month();
int get_day();

public:
void check_date();
int month;
int day;
};

int main()
{
DayOfYear today,yj_birthday(8,23);
cout <<"enter today's date\n";
today.input();
cout <<"yj's birthday is";
yj_birthday.output();

if(equal(today,yj_birthday))
cout <<"happy birthday yangjie!\n";
else
cout <<"happy unbirthday yangjie!\n";

return 0;
}

bool equal(DayOfYear date1, DayOfYear date2)
{

return(date1.month==date2.month&&date1.day==date2.day);

}

DayOfYear::DayOfYear(int the_month, int the_day)
{
month=the_month;
day=the_day;
check_date();
}

int DayOfYear::get_month()
{
return month;
}

int DayOfYear::get_day()
{
return day;
}

void DayOfYear::input()
{
cout <<"enter the month as a number:";
cin>>month;
cout <<"enter the day of the month:";
cin>>day;
}

void DayOfYear::output()
{
cout <<"month=" <<month
<<",day=" <<day <<endl;
}

void DayOfYear::check_date()
{
if((month <1)|(month>12)|(day <1)|(day>31))
{
cout <<"Illegal date. aborting program.\n";
exit(1);
}
}

[lingyin55]

打个vc6的补丁看看有没有效果。

[Quote=引用 4 楼 Paradin 的回复:]
第二个版本，把equal的定义和声明放一起试试
[/Quote]

[yj19888239]

我试试~~~

[yj19888239]

[Quote=引用 4 楼 Paradin 的回复:]
第二个版本，把equal的定义和声明放一起试试
[/Quote]
还是不行

sp6补丁也打上了~~~也不行

[qzl123666]

用VS2008一楼的没有问题啊

[hjjdebug]

lz 代码在vc6下编译没有问题，我不知道自己是否打sp6补丁，可能没有打。

[lpf000]

带sp6补丁的 就应该可以，不过楼主说不行，你把友元函数放在类前声明看看加2句：
class DayOfYear;
bool equal(DayOfYear date1, DayOfYear date2);
class DayOfYear
{
};

[T技术沙龙]

呵呵，后面那个应该是编程软件的自身问题吧，楼主退出环境之后在重新编译估计能过

[lingyin55]

rebuild All一下。

[bobo_guan]

[Quote=引用 5 楼 Paradin 的回复:]
VC6对友元的支持是不好
打个sp6
或者改成 <iostream.h>再去掉using...试试
[/Quote]

vc6的名字空间和友元有点冲突

不要同时使用

[sjsunshinesj]

我也试试看

[Sou2012]

[Quote=引用 5 楼 Paradin 的回复:]
VC6对友元的支持是不好
打个sp6
或者改成 <iostream.h>再去掉using...试试
[/Quote]

晕。。

[aaaa3105563]

顶·

[baihacker]

//如下代码在g++中没有问题
//不要用VC6...支持不好...

#include <iostream> 
using namespace std; 

class DayOfYear 
{ 
public: 
friend bool equal(DayOfYear date1, DayOfYear date2); 

DayOfYear(int the_month, int the_day); 
DayOfYear(){} 

void input(); 
void output(); 

int get_month(); 
int get_day(); 

private: 
void check_date(); 
int month; 
int day; 
}; 

int main() 
{ 
DayOfYear today,yj_birthday(8,23); 
cout <<"enter today's date\n"; 
today.input(); 
cout <<"yj's birthday is"; 
yj_birthday.output(); 

if(equal(today,yj_birthday)) 
cout <<"happy birthday yangjie!\n"; 
else 
cout <<"happy unbirthday yangjie!\n"; 

return 0; 
} 

bool equal(DayOfYear date1, DayOfYear date2) 
{ 

return(date1.month==date2.month&&date1.day==date2.day); 

} 

DayOfYear::DayOfYear(int the_month, int the_day) 
{ 
month=the_month; 
day=the_day; 
check_date(); 
} 

int DayOfYear::get_month() 
{ 
return month; 
} 

int DayOfYear::get_day() 
{ 
return day; 
} 

void DayOfYear::input() 
{ 
cout <<"enter the month as a number:"; 
cin>>month; 
cout <<"enter the day of the month:"; 
cin>>day; 
} 

void DayOfYear::output() 
{ 
cout <<"month=" <<month 
<<",day=" <<day <<endl; 
} 

void DayOfYear::check_date() 
{ 
if((month <1)|(month>12)|(day <1)|(day>31)) 
{ 
cout <<"Illegal date. aborting program.\n"; 
exit(1); 
} 
} 

[mengde007]

VS下面木有问题；

[yj19888239]

哦
受教了
那我们考试用的就是VC6~~~这不是要我们命啊

[Paradin]

第二个版本，把equal的定义和声明放一起试试

[Paradin]

VC6对友元的支持是不好
打个sp6
或者改成<iostream.h>再去掉using...试试