sizeof... operator (since C++11)
Queries the number of elements in a parameter pack.
Syntax
sizeof...( parameter-pack ) |
Returns a constant of type std::size_t.
Explanation
Returns the number of elements in a parameter pack.
Keywords
Example
#include <array>
#include <iostream>
#include <type_traits>
template<typename... Ts>
constexpr auto make_array(Ts&&... ts)
{
using CT = std::common_type_t<Ts...>;
return std::array<CT, sizeof...(Ts)>{std::forward<CT>(ts)...};
}
int main()
{
std::array<double, 4ul> arr = make_array(1, 2.71f, 3.14, '*');
std::cout << "arr = { ";
for (auto s{arr.size()}; double elem : arr)
std::cout << elem << (--s ? ", " : " ");
std::cout << "}\n";
}
Output:
arr = { 1, 2.71, 3.14, 42 }
See also
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https://en.cppreference.com/w/cpp/language/sizeof...
