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std::holds_alternative(3) C++ Standard Libary std::holds_alternative(3) NAME std::holds_alternative - std::holds_alternative Synopsis Defined in header <variant> template< class T, class... Types > constexpr bool holds_alternative( const std::variant<Types...>& v ) (since C++17) noexcept; Checks if the variant v holds the alternative T. The call is ill- formed if T does not appear exactly once in Types... Parameters v - variant to examine Return value true if the variant currently holds the alternative T, false other- wise. Example // Run this code #include <variant> #include <string> #include <iostream> int main() { std::variant<int, std::string> v = "abc"; std::cout << std::boolalpha << "variant holds int? " << std::holds_alternative<int>(v) << '\n' << "variant holds string? " << std::holds_alternative<std::string>(v) << '\n'; } Output: variant holds int? false variant holds string? true See also returns the zero-based index of the alterna- tive held by the index variant (public member function) 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::holds_alternative(3)
NAME | Synopsis | Parameters | Return value | Example | Output: | See also
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