NAME¶

std::make_pair - std::make_pair

Synopsis¶

Defined in header <utility>
template< class T1, class T2 > (until C++11)
std::pair<T1, T2> make_pair( T1 t, T2 u );
template< class T1, class T2 > (since C++11)
std::pair<V1, V2> make_pair( T1&& t, T2&& u ); (constexpr since C++14)

Creates a std::pair object, deducing the target type from the types of arguments.

The deduced types V1 and V2 are std::decay<T1>::type and
std::decay<T2>::type (the usual type transformations applied to
arguments of functions passed by value) unless application of (since C++11)
std::decay results in std::reference_wrapper<X> for some type X, in
which case the deduced type is X&.

Parameters¶

t, u - the values to construct the pair from

Return value¶

A std::pair object containing the given values.

Example¶

// Run this code

#include <functional>
#include <iostream>
#include <utility>

int main()
{
int n = 1;
int a[5] = {1, 2, 3, 4, 5};

// build a pair from two ints
auto p1 = std::make_pair(n, a[1]);
std::cout << "The value of p1 is "
<< '(' << p1.first << ", " << p1.second << ")\n";

// build a pair from a reference to int and an array (decayed to pointer)
auto p2 = std::make_pair(std::ref(n), a);
n = 7;
std::cout << "The value of p2 is "
<< '(' << p2.first << ", " << *(p2.second + 2) << ")\n";
}

Output:¶

The value of p1 is (1, 2)
The value of p2 is (7, 3)

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 181 C++98 the parameter types were const-reference changed these
types, which made passing arrays impossible types to value types