Exceptions

Questions 1 to 5 of 6

1. 1. What does this program print? ``cpp #include <iostream> #include <stdexcept> #include <string> class BankError : public std::runtime_error { public: using std::runtime_error::runtime_error; }; class FrozenError : public BankError { public: FrozenError() : BankError("frozen") {} }; void run(int n) { try { if (n == 1) throw FrozenError{}; if (n == 2) throw BankError("generic"); std::cout << "ok\n"; } catch (const FrozenError& e) { std::cout << "frozen handler: " << e.what() << "\n"; } catch (const BankError& e) { std::cout << "bank handler: " << e.what() << "\n"; } } int main() { run(0); run(1); run(2); } ``

   ok, bank handler: frozen, bank handler: genericok, frozen handler: frozen, bank handler: genericok, frozen handler: frozen, frozen handler: genericok, bank handler: frozen, frozen handler: generic
2. 2. Why must a derived catch block come before a base catch block?

   The compiler accepts only derived types in a catch listCatch blocks run every matching handler in turn, so order does not matterCatch blocks are checked in the order written, and the first match runs, so a base handler first takes every derived errorA base type cannot be caught at all, so the base block is skipped
3. 3. Order the rules for writing a custom C++ exception class, from first to last.

   Use the arrows to put the steps in order.

   1. 1.Add fields for the extra data, and give them getter functions↑↓
   2. 2.Catch the exception by const reference↑↓
   3. 3.Pass the message to the base class, which stores it for what()↑↓
   4. 4.Inherit from a standard exception class, usually std::runtime_error↑↓
4. 4. What does this program print? ``cpp #include <iostream> #include <stdexcept> class Account { public: explicit Account(int b) : balance_(b) {} void withdraw(int amount) { if (amount > balance_) throw std::runtime_error("short"); balance_ -= amount; } int balance() const { return balance_; } private: int balance_; }; int main() { Account a{100}; try { a.withdraw(30); a.withdraw(90); } catch (const std::runtime_error& e) { std::cout << e.what() << " " << a.balance() << "\n"; } } ``

   short 100Nothing prints, because the throw ends the programshort 70short 40
5. 5. The Email constructor throws when the text has no @. The program tries Email bad{"ana.example.com"}; inside a try block. Which statement is true?

   bad exists, but its address is emptybad never exists, because the throw leaves the constructor before the caller gets an objectbad exists, and address() returns the text without the @ checkThe program stops at once with std::terminate, even inside the try block