std::make_tuple
From cppreference.com
Defined in header
<tuple>
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template< class... Types >
tuple<VTypes...> make_tuple( Types&&... args ); |
(since C++11) (until C++14) |
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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&
.
Contents |
[edit] Parameters
args | - | zero or more arguments to construct the tuple from |
[edit] Return value
A std::tuple object containing the given values, created as if by std::tuple<VTypes...>(std::forward<Types>(t)...).
[edit] 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)...); } |
[edit] Example
Run this code
#include <iostream> #include <tuple> #include <functional> int main() { auto t1 = std::make_tuple(10, "Test", 3.14); std::cout << "The value of t1 is " << "(" << std::get<0>(t1) << ", " << std::get<1>(t1) << ", " << std::get<2>(t1) << ")\n"; int n = 1; auto t2 = std::make_tuple(std::ref(n), n); n = 7; std::cout << "The value of t2 is " << "(" << std::get<0>(t2) << ", " << std::get<1>(t2) << ")\n"; }
Output:
The value of t1 is (10, Test, 3.14) The value of t2 is (7, 1)
creates a tuple of lvalue references or unpacks a tuple into individual objects (function template) |
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creates a tuple of rvalue references (function template) |
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creates a tuple by concatenating any number of tuples (function template) |