运算符重载 C++；<< 操作的参数太多
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Operator Overloading C++; too many parameters for << operation
提问by Stanley Cup Phil
I have some code below that will take some names and ages and do some stuff with them. Eventually it will print them out. I need to change my print()function with a global operator<<. I saw on a different forumthat <<operatortakes two parameters, but when I try it I get a "too many parameters for << operation error. Is there something I am doing wrong? I am newer to C++ and I really do not get the point of operator overloading.
我在下面有一些代码，它们将采用一些名称和年龄并用它们做一些事情。最终它会将它们打印出来。我需要print()使用 global更改我的功能operator<<。我在一个不同的论坛上看到它<<operator需要两个参数，但是当我尝试它时，我得到一个“<<操作错误的参数太多。我做错了什么？我是 C++ 的新手，我真的不明白这一点运算符重载。
#include <iostream>;
#include <string>;
#include <vector>;
#include <string.h>;
#include <fstream>;
#include <algorithm>;
using namespace::std;
class Name_Pairs{
vector<string> names;
vector<double> ages;
public:
void read_Names(/*string file*/){
ifstream stream;
string name;
//Open new file
stream.open("names.txt");
//Read file
while(getline(stream, name)){
//Push
names.push_back(name);
}
//Close
stream.close();
}
void read_Ages(){
double age;
//Prompt user for each age
for(int x = 0; x < names.size(); x++)
{
cout << "How old is " + names[x] + "? ";
cin >> age;
cout<<endl;
//Push
ages.push_back(age);
}
}
bool sortNames(){
int size = names.size();
string tName;
//Somethine went wrong
if(size < 1) return false;
//Temp
vector<string> temp = names;
vector<double> tempA = ages;
//Sort Names
sort(names.begin(), names.end());
//High on performance, but ok for small amounts of data
for (int x = 0; x < size; x++){
tName = names[x];
for (int y = 0; y < size; y++){
//If the names are the same, then swap
if (temp[y] == names[x]){
ages[x] = tempA[y];
}
}
}
}
void print(){
for(int x = 0; x < names.size(); x++){
cout << names[x] << " " << ages[x] << endl;
}
}
ostream& operator<<(ostream& out, int x){
return out << names[x] << " " << ages[x] <<endl;
}
};
回答by taocp
You are overloading <<operator as a member function, therefore, the first parameter is implicitly the calling object.
您将<<operator 作为成员函数重载，因此，第一个参数隐式是调用对象。
You should either overload it as friendfunction or as a free function. For example:
您应该将其作为friend函数或自由函数重载。例如：
overloading as friendfunction.
作为friend函数重载。
friend ostream& operator<<(ostream& out, int x){
out << names[x] << " " << ages[x] <<endl;
return out;
}
However, the canonical way is to overload it as freefunction. You can find very good information from this post: C++ operator overloading
但是，规范的方法是将其作为free函数重载。您可以从这篇文章中找到非常好的信息：C++ 运算符重载
回答by shivakumar
declare operator overloading function as friend.
将运算符重载函数声明为友元。
friend ostream& operator<<(ostream& out, int x)
{
out << names[x] << " " << ages[x] <<endl;
return out;
}
