Constructs a tuple of references to the arguments in args suitable for forwarding as an argument to a function. The tuple has rvalue reference data members when rvalues are used as arguments, and otherwise has lvalue reference data members.
[edit] Parameters args - zero or more arguments to construct the tuple from [edit] Return valueA std::tuple object created as if by std::tuple<Types&&...>(std::forward<Types>(args)...)
[edit] NotesIf the arguments are temporaries, forward_as_tuple does not extend their lifetime; they have to be used before the end of the full expression.
#include <iostream>
#include <map>
#include <string>
#include <tuple>
int main()
{
std::map<int, std::string> m;
m.emplace(std::piecewise_construct,
std::forward_as_tuple(6),
std::forward_as_tuple(9, 'g'));
std::cout << "m[6] = " << m[6] << '\n';
// The following is an error: it produces a
// std::tuple<int&&, char&&> holding two dangling references.
//
// auto t = std::forward_as_tuple(20, 'a');
// m.emplace(std::piecewise_construct, std::forward_as_tuple(10), t);
}
Output:
[edit] See also creates atuple object of the type defined by the argument types
tuple by concatenating any number of tuples
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