std::variant::index
From cppreference.com
| constexpr std::size_t index() const |
(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
Exceptions
noexcept specification:
noexcept
Example
Run this code
#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'; }
Output:
v.index = 1 v.index = 0
See also
| (C++17) |
checks if a given type appears exactly once in a variant (function template) |
| (C++17) |
reads the value of the variant given the index or the type (if the type is unique), throws on error (function template) |