Difference between revisions of "cpp/utility/tuple/make tuple"
From cppreference.com
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{{dcl | since=c++11 | until=c++14 | 1= | {{dcl | since=c++11 | until=c++14 | 1= | ||
template< class... Types > | template< class... Types > | ||
| − | tuple<VTypes...> make_tuple( Types&&... args ); | + | {{lc|std::tuple}}<VTypes...> make_tuple( Types&&... args ); |
}} | }} | ||
{{dcl | since=c++14 | 1= | {{dcl | since=c++14 | 1= | ||
template< class... Types > | template< class... Types > | ||
| − | constexpr tuple<VTypes...> make_tuple( Types&&... args ); | + | constexpr {{lc|std::tuple}}<VTypes...> make_tuple( Types&&... args ); |
}} | }} | ||
{{dcl rev end}} | {{dcl rev end}} | ||
Revision as of 15:26, 14 December 2013
| Defined in header <tuple>
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| template< class... Types > <span class="t-lc">[[cpp/utility/tuple|std::tuple]]</span><VTypes...> make_tuple( Types&&... args ); |
(since C++11) (until C++14) |
|
| template< class... Types > constexpr <span class="t-lc">[[cpp/utility/tuple|std::tuple]]</span><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 |
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
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)
| (C++11) |
creates a tuple of lvalue references or unpacks a tuple into individual objects (function template) |
| (C++11) |
creates a tuple of forwarding references (function template) |
| (C++11) |
creates a tuple by concatenating any number of tuples (function template) |
