使用Vs编译成功，可以运行，但是使用G++编译就各种问题，求大神解答 - 编程论坛

#2

z11437096082016-04-03 16:17

程序代码：

#include <iostream>
#include "stonewt.h"
using namespace std;

Stonewt::~Stonewt()
{

}

Stonewt::Stonewt()
{
    stone=pounds=pds_left=0;
}

Stonewt::Stonewt(double pds)
{
    cout<<"调用了一个参数的构造函数"<<endl;
    stone=int(pds)/Lbs_per_Sto;
    pds_left=int(pds)%Lbs_per_Sto+pds-int(pds);
    pounds=pds;
}

Stonewt::Stonewt(double st, double p_left)
{
    cout<<"调用了2个参数的构造函数"<<endl;
    stone=st;
    pds_left=p_left;
    pounds=st*Lbs_per_Sto+p_left;
}

void Stonewt::show()
{
    cout<<pounds<<endl;
}

Stonewt::operator int() const
{
    return int(pounds+0.5);
}

Stonewt::operator double() const
{
    return double(pounds);
}

Stonewt Stonewt::operator+(double pds) const
{
    Stonewt temp;
    temp=pounds+pds;
    return temp;
}
/*
Stonewt operator+(double pds, const Stonewt &p)
{
    return p+pds;
}
*/
ostream & operator<<(ostream &io, Stonewt &p)
{
    cout<<"调用<<重载"<<endl;
    io<<p.pounds<<endl;
    return io;

}

#3

z11437096082016-04-03 16:18

程序代码：

#include <iostream>
#include "stonewt.h"

using namespace std;

int main()
{
    Stonewt poppins(9,2.8);
    double p_w = poppins;
    cout<<"p_w="<<p_w<<endl;
    int p_i= poppins;
    cout<<"p_i="<<p_i<<endl;
    Stonewt ny=19.8;
    ny.show();
    Stonewt nm=20.1+ny;
    nm.show();
    cout<<nm<<endl;
    system("pause");
    return 0;
}

#4

z11437096082016-04-03 16:19

分成以上三个文件，VS中是可以运行的，不知道为什么G++编译就出错了
stonewt.h:19:9: error: ‘ostream’ in namespace ‘std’ does not name a type
  friend std::ostream & operator<<(std::ostream &io,Stonewt &t);
         ^
stonewt.h: In function ‘Stonewt operator+(double, const Stonewt&)’:
stonewt.h:22:3: error: ‘cout’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
   ^
stonewt.h:22:36: error: ‘endl’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
                                    ^
main.cpp: In function ‘int main()’:
main.cpp:18:16: error: ‘system’ was not declared in this scope
  system("pause");
                ^
zyf@ubuntu:~/Desktop/test$ g++ stonewt.h stone1.cpp main.cpp
stonewt.h:19:9: error: ‘ostream’ in namespace ‘std’ does not name a type
  friend std::ostream & operator<<(std::ostream &io,Stonewt &t);
         ^
stonewt.h: In function ‘Stonewt operator+(double, const Stonewt&)’:
stonewt.h:22:3: error: ‘cout’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
   ^
stonewt.h:22:36: error: ‘endl’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
                                    ^
zyf@ubuntu:~/Desktop/test$ g++ stonewt.h
stonewt.h:19:9: error: ‘ostream’ in namespace ‘std’ does not name a type
  friend std::ostream & operator<<(std::ostream &io,Stonewt &t);
         ^
stonewt.h: In function ‘Stonewt operator+(double, const Stonewt&)’:
stonewt.h:22:3: error: ‘cout’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
   ^
stonewt.h:22:36: error: ‘endl’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
                                    ^
zyf@ubuntu:~/Desktop/test$ clear

zyf@ubuntu:~/Desktop/test$ g++ stonewt.h
stonewt.h:19:9: error: ‘ostream’ in namespace ‘std’ does not name a type
  friend std::ostream & operator<<(std::ostream &io,Stonewt &t);
         ^
stonewt.h: In function ‘Stonewt operator+(double, const Stonewt&)’:
stonewt.h:22:3: error: ‘cout’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
   ^
stonewt.h:22:36: error: ‘endl’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
                                    ^
zyf@ubuntu:~/Desktop/test$ g++ -i stonewt.h
g++: error: unrecognized command line option ‘-i’
zyf@ubuntu:~/Desktop/test$ g++ stonewt.h stone1.cpp main.cpp
stonewt.h:19:9: error: ‘ostream’ in namespace ‘std’ does not name a type
  friend std::ostream & operator<<(std::ostream &io,Stonewt &t);
         ^
stonewt.h: In function ‘Stonewt operator+(double, const Stonewt&)’:
stonewt.h:22:3: error: ‘cout’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;
   ^
stonewt.h:22:36: error: ‘endl’ is not a member of ‘std’
   std::cout<<"调用友元函数"<<std::endl;

#5

z11437096082016-04-03 16:20

求大神解惑，谢谢

#6

z11437096082016-04-03 16:32

没人吗？

#7

hjx11202016-04-03 17:53

可能是你的‘stonewt.h’头文件没有引用<iostream>头文件

#8

alice_usnet2016-04-03 18:27

～Stonewt();

#9

z11437096082016-04-03 22:59

回复 7楼 hjx1120

我刚刚在头文件中加了#include<iostream> 程序就不报错了，可是为什么呢？使用ostream时，我加了实std::的

#10

hjx11202016-04-03 23:36

没有加载支持的头文件，声明名称空间有什么用
简单的例子：

程序代码：

int main()
{
std::cout << "请叫我大神";
return 0;

}

不引用iostream是没法编译通过的