error c2679.Error 1 error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'std::vector<_Ty>'

Question

i write this simple program below to use vector but here is error can anyone help ?

#include <iostream>
#include <vector>
#include <fstream>

using namespace std;

void main()
{
    vector<int>a(10,1);
    cout<<a<<endl;
}

Refer to [this question](http://stackoverflow.com/questions/10750057/c-printing-out-the-contents-of-a-vector) if you want to know how to output a vector. — Theolodis, Feb 24 '15 at 07:53
The error message is pretty clear - you can't use << to stream out a vector. — Lubo Antonov, Feb 24 '15 at 07:53
@LuboAntonov how to display any vector?can you send me simple 1st stage program for beginner learner?thanks — faiz ul islam, Feb 25 '15 at 05:25

score 0 · Answer 1 · answered Feb 24 '15 at 08:00

There is no operator<<(ostream&, vector const&). You can provide one yourself:

ostream& operator<<(ostream& os, vector<int> const& v) {
    for (int i=0; i<v.size(); ++i) {
        os << v[i] <<  ", ";
    }
    return os;
}

Put this code before your main function, and it should work.

score 0 · Answer 2 · answered Feb 24 '15 at 08:51

Try this:

std::ostream& operator<<(std::ostream& stream, std::vector<int> const& vec) {
    for (auto it = vec.begin(); it != vec.end(); it++) {
        stream << *it <<  " ";
    }
    return stream;
}

Or:

template <typename T>
std::ostream& operator<<(std::ostream& stream, std::vector<T> const& vec) {
    for (auto it = vec.begin(); it != vec.end(); it++) {
        stream << *it <<  " ";
    }
    return stream;
}

(but make sure the << operator is overloeaded for T)

And if you don't want to overload the << operator:

for (auto& item : a) {
    std::cout << item << " ";
}

error c2679.Error 1 error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'std::vector<_Ty>'

2 Answers2