PDA Simulator

A Pushdown Automata simulator built with Flask.

This project lets you test strings against predefined context-free language patterns and view each computation step, including state, remaining input, and stack contents.

Features

• Web interface for interactive simulation
• Step-by-step trace output
• Accept/Reject result with dead-state visibility
• CLI mode for terminal-based runs
• 11 built-in PDA language definitions
• Ready-to-deploy Vercel configuration

Supported Languages

Choose one of the following language sets in the UI or CLI:

1. L = { a^n b^n : n >= 0 }
2. L = { a^n b^(2n) : n >= 0 }
3. L = { a^m b^n c^(m+n) : m,n >= 0 }
4. L = { a^n b^m c^m d^n : m,n >= 0 }
5. L = { w c w^R : w in {a,b}* }
6. L = { w w^R : w in {a,b}* }
7. L = { a^m b^n : m >= n >= 0 }
8. Balanced parentheses
9. L = { a^n b^n c^m : n,m >= 0 }
10. L = { w in {a,b}* : #a = #b }
11. L = { a^n b^n } U { a^n b^(2n) }

Tech Stack

• Python 3.11
• Flask
• HTML + Tailwind CSS + JavaScript

Project Structure

• app.py: Flask routes and API endpoint
• pda.py: PDA engine and transition execution logic
• lang.py: predefined PDA language configurations
• runner.py: command-line simulator
• templates/index.html: web interface
• api/index.py: Vercel serverless entry point
• vercel.json: Vercel routing/build configuration
• requirements.txt: dependencies

Run Locally

1. Create and activate a virtual environment.

   Windows PowerShell:

   python -m venv .venv
   .\.venv\Scripts\Activate.ps1

   macOS/Linux:

   python -m venv .venv
   source .venv/bin/activate

2. Install dependencies:

   pip install -r requirements.txt

3. Start the app:

   python app.py

4. Open in browser:

   http://127.0.0.1:5000

CLI Usage

Run the simulator from terminal:

python runner.py -i <language_id>

Example:

python runner.py -i 1

Then type the input string when prompted.

Final Notes

• This simulator is designed for learning, experimentation, and classroom demos.
• You can extend it by adding new PDA definitions in lang.py.
• For deployments, keep vercel.json, api/index.py, and requirements.txt in sync.

Contributing

Contributions are welcome.

1. Fork the repository.
2. Create a feature branch.
3. Commit your changes.
4. Open a pull request with a clear description.

Contributors

View the full contributors graph (including commit counts): Contributors Graph

Acknowledgment

If this project helps your automata theory practice, consider starring the repository and sharing it with classmates.