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std::variant::index(3) C++ Standard Libary std::variant::index(3) NAME std::variant::index - std::variant::index Synopsis 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. 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 holds_alternative checks if a variant currently holds a given type (C++17) (function template) std::get(std::variant) reads the value of the variant given the in- dex or the type (C++17) (if the type is unique), throws on error (function template) http://cppreference.com 2022.07.31 std::variant::index(3)
NAME | Synopsis | Example | Output: | See also
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