| Defined in header <tuple> | ||
|---|---|---|
template< class... Types > tuple<VTypes...> make_tuple( Types&&... args ); | (since C++11) (until C++14) | |
template< class... Types > constexpr tuple<VTypes...> make_tuple( Types&&... args ); | (since C++14) |
Creates a tuple object, deducing the target type from the types of arguments.
For each Ti in Types..., the corresponding type Vi in Vtypes... is std::decay<Ti>::type unless application of std::decay results in std::reference_wrapper<X> for some type X, in which case the deduced type is X&.
Parameters
| args | - | zero or more arguments to construct the tuple from |
Return value
A std::tuple object containing the given values, created as if by std::tuple<VTypes...>(std::forward<Types>(t)...).
Possible implementation
template <class T>
struct special_decay
{
using type = typename std::decay<T>::type;
};
template <class T>
struct special_decay<std::reference_wrapper<T>>
{
using type = T&;
};
template <class T>
using special_decay_t = typename special_decay<T>::type;
template <class... Types>
auto make_tuple(Types&&... args)
{
return std::tuple<special_decay_t<Types>...>(std::forward<Types>(args)...);
} |
Example
#include <iostream>
#include <tuple>
#include <functional>
std::tuple<int, int> f() // this function returns multiple values
{
int x = 5;
return std::make_tuple(x, 7); // return {x,7}; in C++17
}
int main()
{
// heterogeneous tuple construction
int n = 1;
auto t = std::make_tuple(10, "Test", 3.14, std::ref(n), n);
n = 7;
std::cout << "The value of t is " << "("
<< std::get<0>(t) << ", " << std::get<1>(t) << ", "
<< std::get<2>(t) << ", " << std::get<3>(t) << ", "
<< std::get<4>(t) << ")\n";
// function returning multiple values
int a, b;
std::tie(a, b) = f();
std::cout << a << " " << b << "\n";
}Output:
The value of t1 is (10, Test, 3.14, 7, 1) 5 7
creates a tuple of lvalue references or unpacks a tuple into individual objects (function template) | |
creates a tuple of rvalue references (function template) | |
creates a tuple by concatenating any number of tuples (function template) |
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