🧠 Compiler Lexer Implementation using JFlex

📌 Overview

This project implements the lexical analysis phase of a compiler as part of a Compiler Design course.

The lexer is built using JFlex and is responsible for recognizing and categorizing input tokens such as:

• Identifiers
• Keywords
• Operators
• Separators
• Numeric literals (multiple types)

The program reads an input file and prints tokens in the specified formatted output.

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🛠 Technologies Used

• Java
• JFlex (Lexical Analyzer Generator)

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📂 Project Structure

compiler-lexer-jflex/
├──docs/
│ └── report.pdf
├── src/
│ ├── Parser.flex # JFlex specification file
│ ├── Parser.java # Generated lexer (from JFlex)
│ └── test.txt # Sample input file
└── README.md

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⚙️ How It Works

1️⃣ Token Recognition

The Parser.flex file defines regular expressions for:

• Keywords
• Operators
• Separators
• Identifiers
• Numeric constants

Each matched token is printed in a formatted structure defined in the project requirements.

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▶️ How to Run

Step 1: Generate Java file using JFlex

Run JFlex on the specification file: jflex Parser.flex

This generates: Parser.java

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Step 2: Compile the generated file

javac Parser.java

This creates: Parser.class

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Step 3: Execute with input file

Place test.txt in the same directory and run: java Parser test.txt

The output tokens will be printed to the console.

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📌 Features

• Pattern-based token recognition
• Structured token output
• Modular lexical rule definitions
• Clean separation between specification and generated code

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🎯 Academic Context

This project demonstrates:

• Practical implementation of lexical analysis
• Usage of lexical analyzer generators
• Regular expression–based tokenization
• Foundations of compiler front-end design

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📄 Notes

• Parser.java is generated automatically from Parser.flex
• The .class file is not included in the repository
• IDE configuration files are excluded via .gitignore

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🔒 License

This project is provided for educational purposes. You may reuse or modify the code with proper attribution.

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