CODEWITHSUNDEEP
c++operator-overloading
Soatl
Soatl

Reputation: 10592

Operator Overloading C++; too many parameters for << operation

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 forum that <<operator takes 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.

#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;
    }
};

Upvotes: 19

Views: 56822

Answers (2)

shivakumar
shivakumar

Reputation: 3397

declare operator overloading function as friend.

friend ostream& operator<<(ostream& out, int x)
{
        out << names[x] << " " << ages[x] <<endl;
        return out;
}

Upvotes: 6

taocp
taocp

Reputation: 23634

You are overloading << operator as a member function, therefore, the first parameter is implicitly the calling object.

You should either overload it as friend function or as a free function. For example:

overloading as friend function.

friend ostream& operator<<(ostream& out, int x){
     out << names[x] << " " << ages[x] <<endl;
     return out;
}

However, the canonical way is to overload it as free function. You can find very good information from this post: C++ operator overloading

Upvotes: 35

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