Rules:

• Your programs must compile without warning using g++ -g -Wall -Wextra -Wconversion -Wsign-conversion -O -std=c++20 main.cpp matrix.cpp
• Test your programs with different values. For now, the speed of your program is irrelevant. So don’t spend time on optimization
• You must check for the appropriate preconditions/postconditions. Your program shouldn’t crash or have undefined behaviour (hint: use asserts)!
• Your programs must be well-structured and documented. Use ctrl-x t in Emacs to pretty-print it. Marks are assigned to functionality, program appearance, and comments.
• In case your program hangs, use ctrl-c to terminate it.
• Remember that you need to include the appropriate header files. To find out which ones you need for specific functions such as printf, use the man command.
• Submit your solution files matrix.cpp on Canvas.

Matrix Implementation Exercise

In this lab, you will implement a Matrix data structure in C++ to represent a 2D matrix using a 1D array in row-major order.

Before you begin implementing the Matrix class, it is necessary to understand how to properly initialize a class’s member variables.

Background

Constructor Initialization: Member Initializer Lists

When defining a constructor for a type, you will will need to assign initial values to its member variables. While assigning values inside the constructor body is usually possible, there is a more direct and efficient way to do this in C++: using a member initializer list.

Consider the following guiding questions:

• How can we initialize member variables before any code in the constructor body runs?
• How can we ensure that all members have valid initial values?
• What happens if a member is const or a reference — can it be assigned later?

To address these concerns, C++ provides a member initializer list syntax, which is evaluated before the constructor body. This technique is especially important when initializing:

• const members and references (which must be initialized exactly once),
• complex types or resources like dynamically allocated memory,
• and to ensure consistency and clarity of object construction.

Example:

Suppose we have the following structure:

struct Point {
    int x;
    int y;

    Point(int a, int b)
        : x(a), y(b)
    {
        // constructor body
    }
};

In this example, x and y are initialized directly using the arguments a and b. This approach avoids unnecessary default construction or reassignment. The part: x(a), y(b) is called the member initializer list.

To learn more, see the official documentation at: cppreference.com: Member initializer list

Problem

You are provided with the following starter files:

• matrix.h — the header file declaring the Matrix struct and its associated methods.
• matrix.cpp — an incomplete implementation file that you will complete.
• main.cpp — a sample driver to help you test your implementation.

Your goal is to complete matrix.cpp by implementing all the functions declared in matrix.h (Do not modify matrix.h), and test your Matrix in main.cpp. You should use dynamic memory allocation (new[] and delete[]) to manage the 1D array backing the matrix.

Compiling and Testing

Compile your program using the following command:

g++ -g -Wall -Wextra -Wconversion -Wsign-conversion -O -std=c++17 matrix.cpp main.cpp

Before submitting, make sure your implementation does not leak memory. Use valgrind to verify:

valgrind --leak-check=full --show-leak-kinds=all --track-origins=yes --verbose ./a.out

Solutions