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| Member functions | ||||
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| Non-member functions | ||||
make_pair | ||||
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) | ||||
(C++11) | ||||
(C++11) | ||||
| Helper classes | ||||
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| Deduction guides(C++17) |
Defined in header <utility> | ||
template<class T1,class T2> std::pair<T1, T2> make_pair( T1 x, T2 y); | (until C++11) | |
template<class T1,class T2> std::pair</*V1*/,/*V2*/> make_pair( T1&& x, T2&& y); | (since C++11) (constexpr since C++14) (until C++20) | |
template<class T1,class T2> constexprstd::pair<std::unwrap_ref_decay_t<T1>, | (since C++20) | |
Creates astd::pair object, deducing the target type from the types of arguments.
Given typesstd::decay<T1>::type as
| (since C++11) (until C++20) |
Contents |
| x, y | - | the values to construct the pair from |
std::pair<T1, T2>(x, y) | (until C++11) |
std::pair</*V1*/,/*V2*/>(std::forward<T1>(x),std::forward<T2>(y)) | (since C++11) (until C++20) |
std::pair<std::unwrap_ref_decay_t<T1>,std::unwrap_ref_decay_t<T2>> | (since C++20) |
#include <functional>#include <iostream>#include <utility> int main(){int n=1;int a[5]={1,2,3,4,5}; // build a pair from two intsauto 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)
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 types, which made passing arrays impossible | changed these types to value types |
