#includeIn this example, the `getInt` function returns an optional integer value. If the `flag` parameter is true, it returns an optional containing the value 42. Otherwise, it returns an empty optional. The `main` function calls `getInt` with the `flag` parameter set to true, and stores the result in the `num` variable. It then checks if a value is present using the `has_value` method, and if so, outputs the value using the `value` method. The "std::optional" class is part of the C++ standard library, and is included in the header file "optional."#include std::optional getInt(bool flag) { if (flag) return 42; else return {}; // returns an empty optional, indicating the absence of a value } int main() { std::optional num = getInt(true); if (num.has_value()) { std::cout << "The value is: " << num.value() << std::endl; } else { std::cout << "No value present." << std::endl; } return 0; }