I have header file like this: class ArrayList { public: // type aliases using value_type = int; using size_type = std::size_t; using reference = value_type&; using const_reference = const value_type&; using pointer = value_type*; using const_pointer = const value_type*; /// Default ctor. Constructs an ArrayList with count copies of the /// default value of value_type, e.g., the default value for an /// int is 0. ArrayList(size_type count = 0); /// Copy constructor. Makes a deep copy of another ArrayList. ArrayList(const ArrayList& other); /// Constructs the container with a copy of the contents of source. ArrayList(const std::initializer_list& source); /// Destructor. virtual ~ArrayList(); /// Accesses the specified element with bounds checking. reference at(size_type pos); const_reference at(size_type pos) const; /// Accesses the first element. /// Calling front on an empty container is undefined. reference front(); const_reference front() const; /// Accesses the last element. /// Calling back on an empty container is undefined. reference back(); const_reference back() const; pointer begin() { return m_data; }; const_pointer begin() const { return m_data; }; pointer end() { return begin() + size(); }; const_pointer end() const { return begin() + size(); }; /// Checks whether the container is empty bool empty() const; /// Returns the number of elements in use. size_type size() const; /// Returns the number of elements that can be held in currently allocated /// storage. size_type capacity() const; /// Clears the contents. After this call, size() returns zero. /// Leaves the capacity() of the container unchanged. void clear(); /// Appends the given element value to the end of the container. If the new size() is greater than capacity(), reallocation occurs. void push_back(const value_type& value); /// Resizes the container to contain count elements. If the current size is greater than count, the container is reduced to its first count elements. If the current size is less than count, additional default constructed elements are appended. void resize(size_type count); /// Exchanges the contents of the container with those of another. Does not invoke any move, copy, or swap operations on individual elements. void swap(ArrayList& other); ArrayList& operator=(const ArrayList&) = delete; protected: size_type m_capacity; ///< The number of elements that can be stored. size_type m_size; ///< The number of elements in use. pointer m_data; ///< Dynamically-allocated array custodian. }; // Array /// Compares the contents of two ArrayLists. Checks that each element in lhs compares equal to each element in rhs at the same position. bool equal(const ArrayList& lhs, const ArrayList& rhs); /// Copies the elements in the range, defined by [first, last), to another range beginning at d_first. void copy(ArrayList::const_pointer first, ArrayList::const_pointer last, ArrayList::pointer d_first); }

Anyone can help me write implementation file with these functions, I stuck this ArrayList, I honestly have no idea to write them, even though I read a book. Hix