std::get(std::pair)
Defined in header <utility> |
||
|---|---|---|
|
(1) | (since C++11) (constexpr since C++14) |
|
(2) | (since C++11) (constexpr since C++14) |
|
(3) | (since C++11) (constexpr since C++14) |
|
(4) | (since C++11) (constexpr since C++14) |
|
(5) | (since C++14) |
|
(6) | (since C++14) |
|
(7) | (since C++14) |
|
(8) | (since C++14) |
|
(9) | (since C++14) |
|
(10) | (since C++14) |
|
(11) | (since C++14) |
|
(12) | (since C++14) |
Extracts an element from the pair using tuple-like interface.
1-4) The index-based overloads fail to compile if the index
I is neither 0 nor 1.
5-12) The type-based overloads fail to compile if the types
T and U are the same.
Parameters
| p | - | pair whose contents to extract |
Return value
1-4) Returns a reference to
p.first if I == 0 and a reference to p.second if I == 1.
5-8) Returns a reference to
p.first.
9-12) Returns a reference to
p.second.
Example
#include <iostream>
#include <utility>
int main()
{
auto p = std::make_pair(1, 3.14);
std::cout << '(' << std::get<0>(p) << ", " << std::get<1>(p) << ")\n";
std::cout << '(' << std::get<int>(p) << ", " << std::get<double>(p) << ")\n";
}Output:
(1, 3.14)
(1, 3.14)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 2485 | C++11 (by index) C++14 (by type) |
there are no overloads for const pair&& | the overloads are added |
See also
| Structured binding (C++17) | binds the specified names to sub-objects or tuple elements of the initializer |
|
(C++11)
|
tuple accesses specified element (function template) |
|
(C++11)
|
accesses an element of an array (function template) |
|
(C++17)
|
reads the value of the variant given the index or the type (if the type is unique), throws on error (function template) |
|
(C++20)
|
obtains iterator or sentinel from a std::ranges::subrange (function template) |
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