关于友元解决输入输出，大家帮忙看下，程序哪里出错了 - C++教室 - C++论坛

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关于友元解决输入输出，大家帮忙看下，程序哪里出错了

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

class F{
    int n;
    int d;
    friend void operator>>(istream& in,F& f);
    friend void operator<<(ostream& out,const F& f);
public:
    F(int n=0,int d=1):n(n),d(d){};

    ~F(){};
};
istream& operator>>(istream& in,F& f){
    char c;
    in>>f.n>>c>>f.d>>endl;
}
ostream& operator<<(ostream& out,const F& f){
    out<<f.n<<'/'<<f.d<<endl;
}
int main ()
{
    F a;
    cin>>a;
    cout<<a;
    return 0;
}
错误提示：C:\Users\kjk\c编程\输入与输出.cpp(17) : error C2248: 'n' : cannot access private member declared in class 'F'
        C:\Users\kjk\c编程\输入与输出.cpp(6) : see declaration of 'n'
C:\Users\kjk\c编程\输入与输出.cpp(17) : error C2248: 'd' : cannot access private member declared in class 'F'
        C:\Users\kjk\c编程\输入与输出.cpp(7) : see declaration of 'd'
C:\Users\kjk\c编程\输入与输出.cpp(17) : error C2679: binary '>>' : no operator defined which takes a right-hand operand of type '' (or there is no acceptable conversion)
C:\Users\kjk\c编程\输入与输出.cpp(20) : error C2248: 'n' : cannot access private member declared in class 'F'
        C:\Users\kjk\c编程\输入与输出.cpp(6) : see declaration of 'n'
C:\Users\kjk\c编程\输入与输出.cpp(20) : error C2248: 'd' : cannot access private member declared in class 'F'
        C:\Users\kjk\c编程\输入与输出.cpp(7) : see declaration of 'd'
C:\Users\kjk\c编程\输入与输出.cpp(25) : error C2593: 'operator >>' is ambiguous
C:\Users\kjk\c编程\输入与输出.cpp(26) : error C2593: 'operator <<' is ambiguous
执行 cl.exe 时出错.

输入与输出.exe - 1 error(s), 0 warning(s)

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第 2 楼

得分:10

这是汉化版vs2010的编译信息

1>  正在创建“Debug\t7.unsuccessfulbuild”，因为已指定“AlwaysCreate”。
1>ClCompile:
1>  stdafx.cpp
1>  t7.cpp
1>d:\c_source\t7\t7\t7.cpp(15): error C2556: “std::istream &operator >>(std::istream &,F &)”: 重载函数与“void operator >>(std::istream &,F &)”只是在返回类型上不同
1>          d:\c_source\t7\t7\t7.cpp(8) : 参见“operator >>”的声明
1>d:\c_source\t7\t7\t7.cpp(15): error C2040: “operator >>”:“std::istream &(std::istream &,F &)”与“void (std::istream &,F &)”的间接寻址级别不同
1>d:\c_source\t7\t7\t7.cpp(17): error C2678: 二进制“>>”: 没有找到接受“std::basic_istream<_Elem,_Traits>”类型的左操作数的运算符(或没有可接受的转换)

1>d:\c_source\t7\t7\t7.cpp(19): error C2556: “std::ostream &operator <<(std::ostream &,const F &)”: 重载函数与“void operator <<(std::ostream &,const F &)”只是在返回类型上不同
1>          d:\c_source\t7\t7\t7.cpp(9) : 参见“operator <<”的声明
1>d:\c_source\t7\t7\t7.cpp(19): error C2040: “operator <<”:“std::ostream &(std::ostream &,const F &)”与“void (std::ostream &,const F &)”的间接寻址级别不同
1>d:\c_source\t7\t7\t7.cpp(25): error C2264: “operator >>”: 函数定义或声明中有错误；未调用函数
1>d:\c_source\t7\t7\t7.cpp(25): error C2088: “>>”: 对于 class 非法
1>d:\c_source\t7\t7\t7.cpp(26): error C2264: “operator <<”: 函数定义或声明中有错误；未调用函数
1>d:\c_source\t7\t7\t7.cpp(26): error C2088: “<<”: 对于 class 非法
1>
1>生成失败。
1>
1>已用时间 00:00:02.93
========== 全部重新生成: 成功 0 个，失败 1 个，跳过 0 个 ==========

DO IT YOURSELF !

第 3 楼

得分:10

#include <iostream>

class F {
public:
    F(int n=0, int d=1) : n_(n), d_(d) {
    };

private:
    int n_;
    int d_;

    friend std::istream& operator>>(std::istream& in, F& f);
    friend std::ostream& operator<<(std::ostream& out, const F& f);
};
std::istream& operator>>(std::istream& in, F& f) {
    char c;
    return in>>f.n_>>c>>f.d_;
}
std::ostream& operator<<(std::ostream& out, const F& f) {
    return out<<f.n_<<'/'<<f.d_;
}

using namespace std;

int main ()
{
    F a;
    cin >> a;
    cout << a << endl;

    return 0;
}