定义ostream运算符<<以对两个结构求和
[英]define ostream operator << to sum two struct
问题描述
i have following code to sum two struct elements 
我有以下代码来总结两个结构元素
#include <iostream>
#include <ostream>
#include <fstream>
using namespace std;
struct USC{
int dollars;
int cents;
USC operator+(const USC o){
USC temp={0,0};
temp.cents=cents+o.cents;
temp.dollars=dollars+o.dollars;
if (temp.cents>=100){
temp.dollars+=1;
temp.cents-=100;
}
return temp;
}
}; /* <-- make sure that semicolon is there */
ostream& operator<<(ostream &output, const USCurrency &o) {
output<<o.dollars<<" "<<o.cents<<endl;
return output;
}
int main(){
USC a={2,50};
USC b={1,75};
USC c=a+b;
cout<<c<<endl;
return 0;
}
but here is a list of errors 但是这里有一个错误列表
1>------ Build started: Project: struct, Configuration: Debug Win32 ------
1> struct.cpp
1>c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23): error C2143: syntax error : missing ';' before '&'
1>c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23): error C2872: 'ostream' : ambiguous symbol
1> could be 'c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23) : USC ostream'
1> or 'c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(636) : std::ostream'
1>c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23): error C2872: 'ostream' : ambiguous symbol
1> could be 'c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23) : USC ostream'
1> or 'c:\program files\microsoft visual studio 10.0\vc\include\iosfwd(636) : std::ostream'
1>c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23): error C2065: 'output' : undeclared identifier
1>c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23): error C2059: syntax error : 'const'
1>c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23): error C2143: syntax error : missing ';' before '{'
1>c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(23): error C2447: '{' : missing function header (old-style formal list?)
1>c:\users\datuashvili\documents\visual studio 2010\projects\struct\struct\struct.cpp(34): error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'USC' (or there is no acceptable conversion)
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(679): could be 'std::basic_ostream<_Elem,_Traits> &std::operator <<<char,std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,const char *)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(726): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<char,std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,char)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(764): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,const char *)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(811): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,char)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(937): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,const signed char *)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(944): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,signed char)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(951): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,const unsigned char *)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(958): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,unsigned char)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(968): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<char,std::char_traits<char>,USC>(std::basic_ostream<_Elem,_Traits> &&,_Ty)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>,
1> _Ty=USC
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(1085): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<char,std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,const std::error_code &)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(186): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(std::basic_ostream<_Elem,_Traits> &(__cdecl *)(std::basic_ostream<_Elem,_Traits> &))'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(192): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(std::basic_ios<_Elem,_Traits> &(__cdecl *)(std::basic_ios<_Elem,_Traits> &))'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(199): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(std::ios_base &(__cdecl *)(std::ios_base &))'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(206): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(std::_Bool)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(226): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(short)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(260): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(unsigned short)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(280): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(int)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(305): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(unsigned int)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(325): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(long)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(345): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(unsigned long)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(366): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(__int64)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(386): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(unsigned __int64)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(407): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(float)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(427): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(double)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(447): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(long double)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(467): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(const void *)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> c:\program files\microsoft visual studio 10.0\vc\include\ostream(487): or 'std::basic_ostream<_Elem,_Traits> &std::basic_ostream<_Elem,_Traits>::operator <<(std::basic_streambuf<_Elem,_Traits> *)'
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> while trying to match the argument list '(std::ostream, USC)'
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
please guys help me what is wrong? 请大家帮我什么是错的？
2 个解决方案
解决方案1
6 已采纳 2011-09-22 05:49:44
You need a semicolon after the struct definition (after the curly brace on line 22) 您需要在结构定义后加上分号（在第22行的花括号之后）
I edited the post to show where it goes 我编辑了帖子以显示其去向
解决方案2
1 2011-09-22 06:10:07
The compiler said it to you: 编译器对您说：
c:\\users\\datuashvili\\documents\\visual studio 2010\\projects\\struct\\struct\\struct.cpp(23): error C2143: syntax error : missing ';'
In general, when you have compilation errors, start from the first one... (-` 通常，当您遇到编译错误时，请从第一个开始...（-
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