Dynamic Memory in C++ (short lab)

An overview of pointers and dynamic memory allocation in C++ is located here.
You need to download (or copy) a file Point23.cpp.

General description of the assignment.

The lab assignment deals with a class Point23.cpp which implements a point that may be two- or three-dimensional, i.e. some instances of the class have 2 coordinates, and some have 3. The coordinates are stored in an array of size 2 or 3 pointed to by a pointer dataPtr. The array is allocated dynamically (i.e. while the program is running) by a class constructor that creates a point.

There are 3 constructors for the class Point23: a constructor that takes two arguments creates a two-dimensional point, a constructor that takes three arguments creates a three-dimensional point, and the default constructor (with no arguments) creates a two-dimensional point with both coordinates initialized to 0s.

The class Point23 provides a class destructor that deallocates the array of coordinates.

Given code contains:

• Interface for the class Point23, i.e. declaration of data fields size and dataPtr and prototypes of all methods.
• Code for methods get_x, get_y, and get_z used in testing of the class, parts of code for the other methods.
• Code for main() that tests the class.

Assignment for the lab.

Comments in the given program mark places where you need to add code for each of the exercises.

• Exercise 1. Write code for dynamic allocation and initialization of the array of coordinates in all three constructors. The array should be pointed to by the pointer dataPtr.
• Exercise 2. Write a line of code in the class destructor ~Point23() that deallocates (i.e. deletes) the array allocated by the constructors.
• Exercise 3. Write a line of code in main() to delete the point allocated by the command new.

Comment

This assignment is just an illustration of dynamic memory allocation. In real-life programs this is not be the best way to implement a 2/3-dimensional point, in particular because overhead of allocating memory dynamically is not worth saving memory for one integer!