Difference between revisions of "cpp/utility/tuple/tuple cat"
From cppreference.com
m (fmt with "multi" wiki-templates, no changes in meaning) |
(Uses tuple-like.) |
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| Line 10: | Line 10: | ||
constexpr std::tuple<CTypes...> tuple_cat( Tuples&&... args ); | constexpr std::tuple<CTypes...> tuple_cat( Tuples&&... args ); | ||
|dcl3= | |dcl3= | ||
| − | template< | + | template< tuple-like... Tuples > |
constexpr std::tuple<CTypes...> tuple_cat( Tuples&&... args ); | constexpr std::tuple<CTypes...> tuple_cat( Tuples&&... args ); | ||
}} | }} | ||
{{dcl end}} | {{dcl end}} | ||
| − | Constructs a tuple that is a concatenation of all tuples in {{ | + | Constructs a tuple that is a concatenation of all tuples in {{c|args}}. |
{{rrev multi|until1=c++23 | {{rrev multi|until1=c++23 | ||
|rev1= | |rev1= | ||
| − | The behavior is undefined if any type in {{c|std::decay_t<Tuples>...}} is not a specialization of {{lc|std::tuple}}. However, an implementation may choose to support types (such as {{lc|std::array}} and {{lc|std::pair}}) that follow the tuple-like protocol. | + | The behavior is undefined if any type in {{c/core|std::decay_t<Tuples>...}} is not a specialization of {{lc|std::tuple}}. However, an implementation may choose to support types (such as {{lc|std::array}} and {{lc|std::pair}}) that follow the tuple-like protocol. |
|rev2= | |rev2= | ||
| − | The types {{c|std::decay_t<Tuples>...}} are constrained to be tuple-like, i.e. each type therein is required to be a specialization of {{lc|std::tuple}} or another type (such as {{lc|std::array}} and {{lc|std::pair}}) that models | + | The types {{c/core|std::decay_t<Tuples>...}} are constrained to be tuple-like, i.e. each type therein is required to be a specialization of {{lc|std::tuple}} or another type (such as {{lc|std::array}} and {{lc|std::pair}}) that models {{rlpi|tuple-like}}. |
}} | }} | ||
| Line 36: | Line 36: | ||
|code= | |code= | ||
#include <iostream> | #include <iostream> | ||
| − | |||
#include <string> | #include <string> | ||
| + | #include <tuple> | ||
// helper function to print a tuple of any size | // helper function to print a tuple of any size | ||
| − | template <class Tuple, std::size_t N> | + | template<class Tuple, std::size_t N> |
struct TuplePrinter | struct TuplePrinter | ||
{ | { | ||
static void print(const Tuple& t) | static void print(const Tuple& t) | ||
{ | { | ||
| − | TuplePrinter<Tuple, N-1>::print(t); | + | TuplePrinter<Tuple, N - 1>::print(t); |
std::cout << ", " << std::get<N-1>(t); | std::cout << ", " << std::get<N-1>(t); | ||
} | } | ||
}; | }; | ||
| − | template <class Tuple> | + | template<class Tuple> |
struct TuplePrinter<Tuple, 1> | struct TuplePrinter<Tuple, 1> | ||
{ | { | ||
| Line 59: | Line 59: | ||
}; | }; | ||
| − | template <typename... Args, std::enable_if_t<sizeof...(Args) == 0, int> = 0> | + | template<typename... Args, std::enable_if_t<sizeof...(Args) == 0, int> = 0> |
void print(const std::tuple<Args...>& t) | void print(const std::tuple<Args...>& t) | ||
{ | { | ||
| Line 65: | Line 65: | ||
} | } | ||
| − | template <typename... Args, std::enable_if_t<sizeof...(Args) != 0, int> = 0> | + | template<typename... Args, std::enable_if_t<sizeof...(Args) != 0, int> = 0> |
void print(const std::tuple<Args...>& t) | void print(const std::tuple<Args...>& t) | ||
{ | { | ||
Revision as of 01:32, 16 May 2023
| Defined in header <tuple>
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||
template< class... Tuples > std::tuple<CTypes...> tuple_cat( Tuples&&... args ); |
(since C++11) (until C++14) |
|
| template< class... Tuples > constexpr std::tuple<CTypes...> tuple_cat( Tuples&&... args ); |
(since C++14) (until C++23) |
|
| template< tuple-like... Tuples > constexpr std::tuple<CTypes...> tuple_cat( Tuples&&... args ); |
(since C++23) | |
Constructs a tuple that is a concatenation of all tuples in args.
|
The behavior is undefined if any type in std::decay_t<Tuples>... is not a specialization of std::tuple. However, an implementation may choose to support types (such as std::array and std::pair) that follow the tuple-like protocol. |
(until C++23) |
|
The types std::decay_t<Tuples>... are constrained to be tuple-like, i.e. each type therein is required to be a specialization of std::tuple or another type (such as std::array and std::pair) that models |
(since C++23) |
Contents |
Parameters
| args | - | zero or more tuples to concatenate |
Return value
A std::tuple object composed of all elements of all argument tuples constructed from std::get<j>(std::forward<Ti>(arg)) for each individual element.
Example
Run this code
#include <iostream> #include <string> #include <tuple> // helper function to print a tuple of any size template<class Tuple, std::size_t N> struct TuplePrinter { static void print(const Tuple& t) { TuplePrinter<Tuple, N - 1>::print(t); std::cout << ", " << std::get<N-1>(t); } }; template<class Tuple> struct TuplePrinter<Tuple, 1> { static void print(const Tuple& t) { std::cout << std::get<0>(t); } }; template<typename... Args, std::enable_if_t<sizeof...(Args) == 0, int> = 0> void print(const std::tuple<Args...>& t) { std::cout << "()\n"; } template<typename... Args, std::enable_if_t<sizeof...(Args) != 0, int> = 0> void print(const std::tuple<Args...>& t) { std::cout << "("; TuplePrinter<decltype(t), sizeof...(Args)>::print(t); std::cout << ")\n"; } // end helper function int main() { std::tuple<int, std::string, float> t1(10, "Test", 3.14); int n = 7; auto t2 = std::tuple_cat(t1, std::make_tuple("Foo", "bar"), t1, std::tie(n)); n = 42; print(t2); }
Output:
(10, Test, 3.14, Foo, bar, 10, Test, 3.14, 42)
See also
| (C++11) |
creates a tuple object of the type defined by the argument types (function template) |
| (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) |
