std::tuple_cat(3)

NAME
std::tuple_cat - std::tuple_cat

Synopsis
   Defined in header <tuple>
   template< class... Tuples > (since C++11)
   std::tuple</* CTypes */...> tuple_cat( Tuples&&... args ); (until C++14)
   template< class... Tuples > (since C++14)
   constexpr std::tuple</* CTypes */...> tuple_cat( Tuples&&... args ); (until C++23)
   template< tuple-like... Tuples > (since C++23)
   constexpr std::tuple</* CTypes */...> tuple_cat( Tuples&&... args );
   Constructs a tuple that is a concatenation of all tuples in args. The element types
   /* CTypes */ of the returned tuple is formed by concatenating the elements type
   packs of all
   std::tuple
   (until C++23)
   tuple-like
   (since C++23) types in Tuples in order.
   The behavior is undefined if any type in std::decay_t<Tuples>... is
   not a specialization of std::tuple. However, an implementation may (until C++23)
   choose to support types (such as std::array and std::pair) that follow
   the tuple-like protocol.
   The types std::decay_t<Tuples>... are constrained to be tuple-like,
   i.e. each type therein is required to be a specialization of (since C++23)
   std::tuple or another type (such as std::array and std::pair) that
   models tuple-like.
   If any type in /* CTypes */ is not constructible from the type of the corresponding
   element in the sequence of elements concatenated from args,
   the behavior is undefined
   (until C++23)
   the program is ill-formed
   (since C++23).

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
   make_tuple creates a tuple object of the type defined by the argument types
   (C++11) (function template)
   tie creates a tuple of lvalue references or unpacks a tuple into
   (C++11) individual objects
                    (function template)
   forward_as_tuple creates a tuple of forwarding references
   (C++11) (function template)