answer:Here's a C++ implementation of the `BankAccount` class: ```cpp #include <iostream> #include <stdexcept> #include <string> class BankAccount { private: std::string account_number; std::string account_holder; double balance; public: // Constructor BankAccount(const std::string& account_number, const std::string& account_holder, double initial_balance) { if (initial_balance <= 0) { throw std::invalid_argument(Initial balance must be positive.); } this->account_number = account_number; this->account_holder = account_holder; this->balance = initial_balance; } // Deposit method void deposit(double amount) { if (amount <= 0) { throw std::invalid_argument(Deposit amount must be positive.); } balance += amount; } // Withdraw method void withdraw(double amount) { if (amount <= 0) { throw std::invalid_argument(Withdrawal amount must be positive.); } if (amount > balance) { throw std::runtime_error(Insufficient funds.); } balance -= amount; } // Get balance method double get_balance() const { return balance; } // Get account info method std::string get_account_info() const { return Account Number: + account_number + nAccount Holder: + account_holder + nBalance: + std::to_string(balance); } }; int main() { try { // Create a new bank account BankAccount account(1234567890, John Doe, 1000.0); // Print initial account info std::cout << account.get_account_info() << std::endl; // Deposit funds account.deposit(500.0); std::cout << Balance after deposit: << account.get_balance() << std::endl; // Withdraw funds account.withdraw(200.0); std::cout << Balance after withdrawal: << account.get_balance() << std::endl; // Attempt to withdraw more than the balance try { account.withdraw(2000.0); } catch (const std::exception& e) { std::cerr << Error: << e.what() << std::endl; } } catch (const std::exception& e) { std::cerr << Error: << e.what() << std::endl; return 1; // Return an error code } return 0; } ``` In this code: * The `BankAccount` class has private member variables for `account_number`, `account_holder`, and `balance`. * The constructor initializes these variables while checking for a positive initial balance. * The `deposit` method adds a positive amount to the balance. * The `withdraw` method subtracts a positive amount from the balance if sufficient funds are available. * The `get_balance` method returns the current balance. * The `get_account_info` method returns a string containing the account information. * The `main` function demonstrates how to create a new bank account, deposit and withdraw funds, and handle errors.

answer:Here's the updated `BankAccount` class with the requested methods and a `Transaction` struct: ```cpp #include <iostream> #include <stdexcept> #include <string> #include <vector> #include <ctime> // Define a Transaction struct struct Transaction { std::string type; double amount; std::time_t timestamp; // Constructor to initialize a Transaction Transaction(const std::string& type, double amount) : type(type), amount(amount), timestamp(std::time(nullptr)) {} // Overload the << operator to print a Transaction friend std::ostream& operator<<(std::ostream& os, const Transaction& transaction) { os << Type: << transaction.type << , Amount: << transaction.amount << , Timestamp: << std::asctime(std::localtime(&transaction.timestamp)); return os; } }; class BankAccount { private: std::string account_number; std::string account_holder; double balance; std::vector<Transaction> transactions; public: // Constructor BankAccount(const std::string& account_number, const std::string& account_holder, double initial_balance) { if (initial_balance <= 0) { throw std::invalid_argument(Initial balance must be positive.); } this->account_number = account_number; this->account_holder = account_holder; this->balance = initial_balance; // Add an initial deposit transaction add_transaction(Transaction(Deposit, initial_balance)); } // Deposit method void deposit(double amount) { if (amount <= 0) { throw std::invalid_argument(Deposit amount must be positive.); } balance += amount; add_transaction(Transaction(Deposit, amount)); } // Withdraw method void withdraw(double amount) { if (amount <= 0) { throw std::invalid_argument(Withdrawal amount must be positive.); } if (amount > balance) { throw std::runtime_error(Insufficient funds.); } balance -= amount; add_transaction(Transaction(Withdrawal, amount)); } // Get balance method double get_balance() const { return balance; } // Get account info method std::string get_account_info() const { return Account Number: + account_number + nAccount Holder: + account_holder + nBalance: + std::to_string(balance); } // Add transaction method void add_transaction(const Transaction& transaction) { transactions.push_back(transaction); } // Get transactions method std::vector<Transaction> get_transactions() const { return transactions; } // Get transaction at method Transaction get_transaction_at(size_t index) const { if (index >= transactions.size()) { throw std::out_of_range(Transaction index out of range.); } return transactions[index]; } }; int main() { try { // Create a new bank account BankAccount account(1234567890, John Doe, 1000.0); // Print initial account info std::cout << account.get_account_info() << std::endl; // Deposit funds account.deposit(500.0); std::cout << Balance after deposit: << account.get_balance() << std::endl; // Withdraw funds account.withdraw(200.0); std::cout << Balance after withdrawal: << account.get_balance() << std::endl; // Print all transactions std::cout << Transactions:n; for (const auto& transaction : account.get_transactions()) { std::cout << transaction << std::endl; } // Attempt to withdraw more than the balance try { account.withdraw(2000.0); } catch (const std::exception& e) { std::cerr << Error: << e.what() << std::endl; } // Get a transaction at a specific index Transaction transaction = account.get_transaction_at(1); std::cout << Transaction at index 1:n << transaction << std::endl; } catch (const std::exception& e) { std::cerr << Error: << e.what() << std::endl; return 1; // Return an error code } return 0; } ``` In this updated code: * A `Transaction` struct represents individual transactions, including the type, amount, and timestamp. * The `BankAccount` class has been updated to include a vector of `Transaction` objects to store the account's transactions. * The `add_transaction` method adds a new transaction to the vector. * The `get_transactions` method returns the vector of all transactions associated with the account. *

answer:In modern C++, the use of raw pointers is discouraged due to their potential for causing memory leaks and dangling pointers. Smart pointers are a safer alternative, automatically managing memory and providing exception safety. **When to use raw pointers:** 1. **Legacy Code**: Raw pointers might still be used in older codebases, and it's essential to be familiar with them when working with legacy code. 2. **Low-Level Programming**: In situations requiring direct memory manipulation, such as device driver development or low-level system programming, raw pointers may be necessary. 3. **Interfacing with C Code**: When working with C code or libraries that use raw pointers, it may be necessary to use them for compatibility. **Smart Pointers:** # unique_ptr A `unique_ptr` exclusively owns the object it points to and automatically frees the memory when it goes out of scope. ```cpp #include <memory> class MyClass { public: MyClass() { std::cout << MyClass constructedn; } ~MyClass() { std::cout << MyClass destroyedn; } }; int main() { std::unique_ptr<MyClass> ptr(new MyClass()); // ptr is the sole owner of the MyClass object // ptr can be moved to another unique_ptr std::unique_ptr<MyClass> newPtr = std::move(ptr); // ptr is now nullptr, newPtr owns the MyClass object return 0; } ``` # shared_ptr A `shared_ptr` shares ownership of the object with other `shared_ptr` instances. The object is automatically freed when the last `shared_ptr` pointing to it goes out of scope. ```cpp #include <memory> class MyClass { public: MyClass() { std::cout << MyClass constructedn; } ~MyClass() { std::cout << MyClass destroyedn; } }; int main() { std::shared_ptr<MyClass> ptr1(new MyClass()); // ptr1 owns the MyClass object { std::shared_ptr<MyClass> ptr2 = ptr1; // ptr1 and ptr2 share ownership of the MyClass object } // ptr2 has gone out of scope, ptr1 still owns the MyClass object return 0; } ``` # weak_ptr A `weak_ptr` observes the object owned by a `shared_ptr` without participating in its ownership. It's used to prevent circular references and to check if the observed object still exists. ```cpp #include <memory> class MyClass { public: MyClass() { std::cout << MyClass constructedn; } ~MyClass() { std::cout << MyClass destroyedn; } }; int main() { std::shared_ptr<MyClass> sharedPtr(new MyClass()); std::weak_ptr<MyClass> weakPtr(sharedPtr); // sharedPtr owns the MyClass object, weakPtr observes it if (std::shared_ptr<MyClass> lockedPtr = weakPtr.lock()) { // lockedPtr points to the MyClass object if it still exists } else { // The MyClass object has been destroyed } return 0; } ``` **Guidelines for choosing smart pointers:** 1. Use `unique_ptr` when an object has a single owner. 2. Use `shared_ptr` when multiple entities share ownership of an object. 3. Use `weak_ptr` to observe an object owned by a `shared_ptr` without taking ownership. By following these guidelines and using smart pointers, you can write safer and more efficient C++ code.

answer:Chester needs to deliver ten bales of hay. Farmer Brown wants double the delivery, so he wants twenty bales of hay. The previous hay cost x per bale, so the cost of the previous hay is 10x. The better quality hay costs 18 per bale, so the cost of the better quality hay is 20 * 18 = 360. To find out how much more money Farmer Brown needs, we subtract the cost of the previous hay from the cost of the better quality hay: 360 - 10x. We are given that Farmer Brown needs 210 more, so we can write: 360 - 10x = 210. Solving for x, we get: x = 15. The value of x is 15. 15 The answer is: 15