sizeof... operator (since C++11)

 

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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

sizeof

Example

Run this code

#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

• sizeof