How to print vector to terminal in c++

Question

I am trying to print a vector of integers to the terminal using "cout", but I get an error message during compiling:

no match for 'operator<<' (operand types are 'std::basic_ostream' and 'std::vector') cout << "Disparity at points: " << disparityVector << endl;

The snippet of code looks like this:

vector<int> disparityVector;

for ( int i=0; i<drawPixels.size(); i++)    // Get disparity at each point of the drawn line
  disparityVector.push_back((int)disparityMapOutput.at<int16_t>(pos[i].y, pos[i].x));

cout << "Disparity at points: " << disparityVector << endl;

There is no error with assigning the values to the vector, only the "cout" part of the code is making errors

You CANT just `cout <<` a vector, you need to iterate on it and cout each value separately. — N.K, May 14 '18 at 08:57
Or you could write your own `std::basic_ostream::operator << (const std::vector&)` as the error suggests — UKMonkey, May 14 '18 at 08:59
I have already used this method to output another vector further up in my code, but this is of type "vector" — eirikaso, May 14 '18 at 09:01
@eirikaso then you probably have a non-templated version, rather than the template in the answer below. — UKMonkey, May 14 '18 at 09:03

score 5 · Answer 1 · answered May 14 '18 at 09:00

For example, using ostream_iterator.

Sample from that page:

// ostream_iterator example
#include <iostream>     // std::cout
#include <iterator>     // std::ostream_iterator
#include <vector>       // std::vector
#include <algorithm>    // std::copy

int main () {
  std::vector<int> myvector;
  for (int i=1; i<10; ++i) myvector.push_back(i*10);

  std::ostream_iterator<int> out_it (std::cout,", ");
  std::copy ( myvector.begin(), myvector.end(), out_it );
  return 0;
}

Kaveh Vahedipour · Accepted Answer · 2018-05-14T13:35:40.013

2

You'll need something like below, if you want to do it the way you've coded it.

template<class T>
inline std::ostream& operator<< (std::ostream& o, std::vector<T> const& v) {
  for (auto const& i : v)
    o << i << " ";
  return o;
}

edited May 14 '18 at 13:35

answered May 14 '18 at 08:59

Kaveh Vahedipour

3,412
1
14
22

1

You could do with a separator – UKMonkey May 14 '18 at 09:02

score 2 · Answer 3 · answered May 14 '18 at 09:04

2

std::ostream& operator<<(std::ostream& os, const vector<int>& v)
{
    std::ostream_iterator<int> _oit(cout, " ");
    std::copy(v.begin(), v.end(), _oit);
    return os;
}

answered May 14 '18 at 09:04

rsy56640

299
1
3
13

score 0 · Answer 4 · answered May 14 '18 at 09:02

0

This error means that vector<T> has no operator<< implementation. You need to iterate over your vector and print each element:

for(int i = 0; i < disparityVector.size; i++) {
    cout << disparityVector[i];
}
cout << endl;

answered May 14 '18 at 09:02

Rafiwui

544
6
19

How to print vector to terminal in c++

4 Answers4