Factory and enums

Questions 1 to 5 of 8

1. 1. What does this program print? ``cpp #include <iomanip> #include <iostream> class Temperature { public: static Temperature from_celsius(double c) { return Temperature{c}; } static Temperature from_fahrenheit(double f) { return Temperature{(f - 32.0) * 5.0 / 9.0}; } double celsius() const { return celsius_; } private: explicit Temperature(double c) : celsius_(c) {} double celsius_; }; int main() { auto a = Temperature::from_fahrenheit(212.0); auto b = Temperature::from_celsius(-5.5); std::cout << std::fixed << std::setprecision(1); std::cout << a.celsius() << ' ' << b.celsius() << '\n'; } ``

   212.0 -5.5100.0 5.5100.0 -5.5180.0 -5.5
2. 2. What does this program print? ``cpp #include <iostream> enum class Coin { penny, nickel, dime, quarter }; constexpr int cents(Coin c) { switch (c) { case Coin::penny: return 1; case Coin::nickel: return 5; case Coin::dime: return 10; case Coin::quarter: return 25; } return 0; } int main() { int total = 0; for (Coin c : {Coin::dime, Coin::quarter, Coin::penny}) { total += cents(c); } std::cout << total << ' ' << static_cast<int>(Coin::quarter) << '\n'; } ``

   36 341 336 235 3
3. 3. Why is the Temperature constructor private in the factory example?

   It makes the constructor run faster when the program startsSo every Temperature is made through a named factory, which shows the unit in each call and keeps each conversion in one placeSo the compiler can turn a plain double into a Temperature on its ownSo Temperature objects cannot be copied
4. 4. Which two words, written at the start of a C++ enum, make its names scoped, so the value must be written Coin::dime and not dime?

   Type your answer.

5. 5. What is the bug in this builder? ``cpp class Builder { public: void port(int value) { port_ = value; } void tls(bool value) { tls_ = value; } private: int port_ = 8080; bool tls_ = false; }; int main() { Builder b; b.port(443).tls(true); } ``

   port is a reserved word in C++, so the name has to changetls(true) needs quotes around trueEach setter returns void, so port(443) gives nothing to call tls on; each setter should return Builder& and end with return *this;Builder needs a constructor that takes the port before it can be created