Exploring Stacks: A Personal Perspective on Their Use in Programming

Understanding Stacks with a Simple Example 

Think of a stack of books on a table. You place one book on top of another, making a tower. When you want a book, you take the one on top. This means the last book you placed is the first one you take out. 

This idea is how stacks in programming work too. A stack follows the Last In, First Out (LIFO) rule. The last thing you add is the first thing you remove. It’s a simple and efficient way to manage data. 

What is a Stack? 

A stack is a linear data structure that follows the Last In, First Out (LIFO) principle. This means that the last element added to the stack is the first one to be removed. A stack can be visualized as a collection of elements where operations are performed only at one end, called the top of the stack. 

Key Operations in a Stack: 

1. Push: Add an element to the top of the stack. 

1. Pop: Remove the top element from the stack. 

1. Peek (or Top): Retrieve the top element without removing it. 

1. IsEmpty: Check if the stack has no elements. 

Why Do We Use Stacks? 

Stacks are a fundamental data structure widely used across various domains because of their unique Last In, First Out (LIFO) behavior. Here’s why stacks are important and how they are applied, including their role in the automotive domain. 

1. Managing Function Calls 

Stacks are critical for managing function calls in programming languages: 

• When a function is called, its details (like local variables and return address) are pushed onto the call stack. 

• Once the function finishes execution, its details are popped off the stack. 

This ensures the proper execution flow, including handling recursive function calls. 

2. Undo/Redo Functionality 

Stacks are widely used in applications like: 

• Text editors: To track and undo actions like typing or deleting. 

• Automotive user interfaces (HMIs): To enable undo/redo actions for user inputs or settings adjustments. For instance, a driver adjusting the seat position or navigation settings can undo the last change if needed. 

3. Expression Evaluation 

Stacks play a key role in evaluating mathematical or logical expressions, particularly in compilers or calculators. 

4. Navigation in Applications 

Stacks manage navigation in software, including automotive applications: 

• Infotainment systems: When a user navigates through menus (e.g., audio settings, navigation maps), previous menus are stored on a stack. This allows the user to go back to the previous menu easily. 

5. Balancing Symbols 

Stacks are used to validate input, ensuring proper syntax and structure in programs and configurations, including automotive diagnostics software. 

6. Game Algorithms 

Games in infotainment systems may use stacks for managing moves or solving puzzles. 

7. Memory Management 

Stacks manage temporary memory in programming, such as for temporary variables in functions. In automotive systems, this is crucial for handling: 

• Real-time embedded software: Managing temporary data like sensor values or system state in ECUs (Electronic Control Units). 

Stacks in the Automotive Domain 

Stacks are particularly important in automotive systems to ensure reliable and efficient operation: 

a) Embedded Systems 

In automotive embedded systems, stacks handle: 

• Interrupt handling: When an interrupt occurs (e.g., from a sensor), the current execution state is pushed onto a stack, allowing the system to respond to the interrupt. Once handled, the system resumes from where it left off. 

• Task switching: Real-time operating systems (RTOS) use stacks to switch between tasks efficiently, ensuring smooth functioning of systems like cruise control or ABS. 

b) Navigation and Infotainment Systems 

• Stacks manage menu navigation in the user interface, allowing users to move back and forth between screens. 

• Stacks also handle routing history in navigation systems, enabling users to retrace their steps or revisit previous destinations. 

c) Diagnostic Systems 

Stacks are used in diagnostic tools to trace errors and manage logs efficiently: 

• Error handling: Faults in systems are tracked and pushed onto a diagnostic stack for debugging. 

• Traceability: Call stacks help identify where a fault occurred in the software. 

d) Autonomous Driving Systems 

Autonomous systems use stacks to manage: 

• Sensor fusion tasks: Temporary data from various sensors (like LiDAR, cameras, and radar) is stored and processed in stacks to make real-time decisions. 

• Pathfinding algorithms: For backtracking in maze-like path planning. 

Manual Implementation of a Stack 

Let’s see how we can manually implement a stack in java withour using built-in libraries like java.util.stack 

Using Java’s Stack Library 

Java provides a built-in Stack class in the java.util package. This class simplifies the implementation of stacks by providing methods like push(), pop(), peek(), and more. 

Here’s how you can use it