std::variant<Types...>::index
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std::variant
variant::index
(C++26)
constexpr std::size_t index() const noexcept;
(since C++17)
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.
[edit] Example
Run this code
#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'; }
Output:
v.index = 1 v.index = 0
[edit] See also
(C++17)
(function template) [edit]