C++ Utility::make_pair() Function

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The C++ std::utility::make_pair() function is used to create a pair object, which is a simple container for storing two heterogeneous values. It allows you to combine the two values into a single object without explicitly specifying the types.

Syntax

Following is the syntax for std::utility::make_pair() function.

pair<V1,V2> make_pair (T1&& x, T2&& y);

Parameters

• x, y − It indicates the values for the members first and second.

Return Value

It returns a pair object whose elements first and second are set to x and y respectivelly.

Exceptions

If the construction or assignment of type T throws.

Data races

If either (or both) T1 or T2 is an rvalue reference type of a type supporting move semantics, its corresponding argument is modified.

Example 1

In the following example, we are going to consider the basic usage of the make_pair() function.

#include <iostream>
#include <utility>
int main() {
   auto x = std::make_pair(1, "Welcome");
   std::cout << "Result : " << x.first << ", " << x.second << std::endl;
   return 0;
}

Output

Output of the above code is as follows −

Result : 1, Welcome

Example 2

Consider the following example, where we are going to use the vector for storing the values.

#include <iostream>
#include <vector>
#include <utility>
int main() {
   std::vector < std::pair < int, char >> x;
   x.push_back(std::make_pair(11, 'A'));
   x.push_back(std::make_pair(13, 'B'));
   for (const auto & p: x) {
      std::cout << "Result : " << p.first << ", " << p.second << std::endl;
   }
   return 0;
}

Output

Following is the output of the above code −

Result : 11, A
Result : 13, B

Example 3

Let's look at the following example, where we are going to use the make_pair() in the map.

#include <iostream>
#include <map>
#include <utility>
int main() {
   std::map < int, std::string > x;
   x.insert(std::make_pair(14, "Hi"));
   x.insert(std::make_pair(12, "Hello"));
   for (const auto & p: x) {
      std::cout << "Result : " << p.first << ", " << p.second << std::endl;
   }
   return 0;
}

Output

If we run the above code it will generate the following output −

Result : 12, Hello
Result : 14, Hi