A **pair in C++** is a container that stores two values (like a tuple). These values may or may not be of the same data-type.

The declaration involves a keyword (`pair`) followed by comma-separated data-types within `< >` signs and the name of the pair.

The elements of a pair can be accessed via the `first` and `second` keywords.

#include <iostream>
using namespace std;

int main() {
  pair<int, string> anon_pair; // Declaring a pair

  anon_pair.first = 17; // Accessing the first element
  anon_pair.second = "seventeen"; // Accessing the second element
}

Alternatively, pairs can also be initialized in the following two ways:

#include <iostream>
using namespace std;

int main() {
  pair<int, string> pair_1(4, "four"); // 1) Declaring and initializing together
  
  pair<int, string> pair_2; // 2) Declaring
  pair_2 = make_pair(5, "five"); //Then initializing using a built-in make_pair function.
}

### Operators
1. The **assignment (`=`) operator** lets us assign the values of one pair to another.
2. The **equality (`==`) operator** returns true if two pairs contain the same values. The **inequality (`!=`) operator** returns true if two pairs *do not* contain the same values.
3. The **less-than (`<`)** and **greater-than (`>`)** operators work by *only* comparing the `first` values of the pairs being compared. The same can be said about the `<=` and `>=` operators.

How one can use these operators​ is demonstrated below:

#include <iostream>
using namespace std;

int main() {
  pair<int, string> pair_1(1, "one"); 
  pair<int, string> pair_2; 
  pair_2 = make_pair(2, "two"); 

  if (pair_1 <= pair_2) // Less-than or equal to
  {  
    pair_1 = pair_2; // Assignment
  }

  if(pair_1 == pair_2) // Equality
  {
    cout<<pair_1.first<<" "<<pair_1.second<<endl;
  }
}

What is a C++ pair?

Code

Operators