SimPL Language Interpreter

SimPL (Simple Programming Language) is a lightweight, statically-typed programming language interpreter built using ANTLR4 and Java. This project demonstrates the implementation of a basic programming language with focus on readability and simplicity.

Project Overview

SimPL is designed as an educational tool to understand language interpretation concepts including:

• Lexical analysis and parsing using ANTLR4
• Abstract Syntax Tree (AST) generation
• Visitor pattern for AST traversal and interpretation
• Type checking and variable management
• Runtime evaluation of expressions

Architecture

The interpreter is structured into several key components:

1. Lexer & Parser (ANTLR4 Generated)

   • Tokenizes input code
   • Generates parse tree based on grammar rules
   • Handles syntax validation

2. Visitor Implementation (SimPLEvaluatorVisitor.java)

   • Traverses the parse tree
   • Manages variable scope and type checking
   • Executes program statements
   • Handles runtime operations

3. Main Application (App.java)

   • Handles file input processing
   • Orchestrates lexing, parsing, and interpretation
   • Manages program execution flow

Features

• Variable declarations with types (int, boolean, string)
• Arithmetic operations (+, -, *, /, %)
• String concatenation
• Print statements
• Type checking
• Runtime error handling

Usage

The interpreter reads code from a file named test.simpl in the current directory. To run the interpreter:

java -jar target/PlangInterpreter-1.0-SNAPSHOT-jar-with-dependencies.jar

Make sure you have a test.simpl file in the same directory before running the program.

Example Program

Create a file named test.simpl with your SimPL code. For example:

var name: string = "World";
var count: int = 3;
print("Hello, " + name);
print(count * 2);

Language Syntax

• Variable declaration: var name: type = value;
• Print statement: print(expression);
• Types: int, boolean, string
• Operators:
  • Arithmetic: +, -, *, /, %
  • String concatenation: +

Development Setup

1. Prerequisites:

   • Java JDK 17 or higher
   • Maven
   • ANTLR4 Plugin

2. Build and run:

mvn clean package && java -jar target/PlangInterpreter-1.0-SNAPSHOT-jar-with-dependencies.jar

Project Structure

PlangInterpreter/
├── src/
│   ├── main/
│   │   ├── antlr4/          # ANTLR4 grammar files
│   │   └── java/
│   │       └── com/
│   │           └── example/  # Java source files
│   └── test/                 # Test cases
├── pom.xml                   # Maven configuration
└── test.simpl               # Example input file

Future Enhancements

Potential areas for expansion include:

• Control flow statements (if/else, loops)
• Function definitions and calls
• Advanced type system
• Standard library functions
• Error recovery and debugging tools