Question

Give the definition of the copy constructor for the class Stack described in Display 13.17.

Short answer

Question: Describe the process for creating a copy constructor for the class Stack, based on Display 13.17. Answer: To create a copy constructor for the class Stack, follow these steps: 1. Identify the class members (stackArray, stackSize, and top). 2. Declare the copy constructor with the signature `Stack(const Stack& other);` 3. Allocate memory for the new stackArray, using the stackSize of the 'other' object. 4. Copy the values of the 'other' object's stackArray using a for loop. 5. Copy the values of 'stackSize' and 'top' from the 'other' object to the new object. 6. Combine all the steps to define the copy constructor. The final copy constructor should be: ```cpp Stack::Stack(const Stack& other) { stackArray = new int[other.stackSize]; for (int i = 0; i < other.stackSize; i++) { stackArray[i] = other.stackArray[i]; } stackSize = other.stackSize; top = other.top; } ```

Step-by-step solution

Identify the Class Members

First, review Display 13.17 and identify the class members that need to be copied in the copy constructor. In this case, the class Stack has the following members: - an integer array called 'stackArray' - an integer called 'stackSize' - an integer called 'top'

Declare the Copy Constructor

Declare the copy constructor with the following signature: ``` Stack(const Stack& other); ``` This constructor accepts a constant reference to another Stack object (named 'other') that will be the source for our copy.

Allocate Memory for the stackArray

In the copy constructor, allocate memory for the 'stackArray' of the new object by using the 'new' keyword, and set the size equal to the 'stackSize' of the 'other' object. ``` stackArray = new int[other.stackSize]; ```

Copy the Values of the other Object

Iterate through the 'stackArray' of the 'other' object and copy each element to the new object's 'stackArray'. Use a for loop to iterate through each element and perform the assignment operation: ``` for (int i = 0; i < other.stackSize; i++) { stackArray[i] = other.stackArray[i]; } ```

Copy the other Object's stackSize and top Values

After copying the 'stackArray' values, copy the 'stackSize' and 'top' values from the 'other' object to the new object: ``` stackSize = other.stackSize; top = other.top; ```

Combine All Steps to Define the Copy Constructor

Now, combine all the steps together to define the copy constructor for the class Stack: ```cpp Stack::Stack(const Stack& other) { stackArray = new int[other.stackSize]; for (int i = 0; i < other.stackSize; i++) { stackArray[i] = other.stackArray[i]; } stackSize = other.stackSize; top = other.top; } ``` With this copy constructor, the class Stack can be initialized by copying the data from an existing object of the same class.

Key concepts

Class Members in C++

When discussing object-oriented programming in C++, class members are at the core of the discussion. A class in C++ is essentially a blueprint for creating objects, which are instances of that class. Class members can be either data members or function members.

Data members, also known as attributes, represent the state of an object. For example, a class representing a 'Stack' might have an integer array to store the stack elements, an integer to track the size of the stack, and another integer to keep track of the topmost element position in the stack. In our exercise, these correspond to 'stackArray', 'stackSize', and 'top'.

Function members, on the other hand, are the operations that can be performed on the objects, such as methods to push or pop elements from the stack. The special member functions of a class include constructors, which are used to initialize new objects, and the copy constructor is particularly important because it defines how an object can be copied, taking careful account of the data members to achieve a proper duplicate of the original object.

Memory Allocation in C++

In C++, memory allocation is a fundamental concept that entails reserving space in the computer's memory to hold data. Using the operator new, we can allocate memory dynamically, which means at runtime. This is crucial for managing resources in applications that require variable amounts of memory.

For instance, when we define a copy constructor and need to copy an array from another object, we cannot merely copy the reference to the existing array. We need to create an entirely new array in memory to hold the copied values, preventing changes to one object from affecting the other. This is achieved through dynamic memory allocation, using expressions like new int[other.stackSize] to allocate an array of integers of the same size as that in the object we are copying.

Array Copying in C++

Copying an array in C++ is more intricate than just copying the elements from one location to another. When dealing with array copying, especially in the context of a copy constructor, we need to perform a deep copy.

This involves creating a new array and then copying each element from the original array into the new one, usually with a loop. In our 'Stack' class example, this is done in the loop:
for (int i = 0; i < other.stackSize; i++) {
stackArray[i] = other.stackArray[i];
}
Here, each element of the original stack's 'stackArray' is iterated over and assigned to the corresponding index of the new 'stackArray', thus ensuring that the original and the copy are fully independent of each other.

Constructor Overloading in C++

Constructor overloading in C++ means defining multiple constructors with different sets of parameters. This allows the creation of objects in different states or with various initializations.

In the case of our 'Stack' class, aside from the default constructor and any other constructors that accept parameters to initialize the object, we also have a copy constructor. The copy constructor has a unique signature that takes a reference to the same class type:
Stack(const Stack& other);
Notably, overloading allows us to cater to different initialization needs, whether we're starting from scratch with the default constructor, initializing with specific values, or creating a copy of an existing 'Stack' object. Each constructor serves its purpose without interfering with the others, demonstrating the power and flexibility of constructor overloading.