std::variant<Types...>:: index

Returns the zero-based index of the alternative that is currently held by the variant.

If the variant is valueless_by_exception , returns variant_npos .

Example

#include <iostream>
#include <string>
#include <variant>
 
int main()
{
    std::variant<int, std::string> v = "abc";
    std::cout << "v.index = " << v.index() << '\n';
    v = {};
    std::cout << "v.index = " << v.index() << '\n';
}

v.index = 1
v.index = 0

See also