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sizeof... operator

From cppreference.com
< cpp‎ | language

Queries the number of elements in a parameter pack.

Contents

[edit] Syntax

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

Returns a constant of type std::size_t.

[edit] Explanation

Returns the number of elements in a parameter pack.

[edit] Keywords

sizeof

[edit] Example

#include <iostream>
#include <array>
#include <type_traits>
 
template<typename... Ts>
constexpr auto make_array(Ts&&... ts)
    -> std::array<std::common_type_t<Ts...>,sizeof...(Ts)>
{
    return { std::forward<Ts>(ts)... };
}
 
int main()
{
    auto b = make_array(1, 2, 3);
    std::cout << b.size() << '\n';
    for (auto i : b)
        std::cout << i << ' ';
}

Output:

3
1 2 3

[edit] See also