std::variant<Types...>::index
Declarations
C++17
constexpr std::size_t index() const noexcept;
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 <variant>
#include <string>
#include <iostream>
int main()
{
std::variant<int, std::string> v = "abc";
std::cout << "v.index = " << v.index() << '\n';
v = {};
std::cout << "v.index = " << v.index() << '\n';
}
Result
v.index = 1
v.index = 0