HL Language Interpreter

Overview

This project implements an interpreter for the HL language. It is built in Java using JavaCC and JJTree to generate and evaluate an Abstract Syntax Tree (AST) with the Visitor pattern.

Project Structure

• HL.jjt
  Grammar Definition: Defines the HL language grammar using JJTree.
• HLEval.java
  Interpreter Logic: Contains the visitor methods to evaluate the AST.
• Makefile
  Automates the compilation and build process.
• runtests
  A script for running test cases located in the tests/ directory.
• tests/
  Directory for HL test files.

Prerequisites

• Java (JDK 11 or newer)
• JavaCC (v7.0.9 or compatible)

Build and Run Instructions

Using Makefile

1. Build the Interpreter

   make

2. Run Tests

   ./runtests

Direct Compilation

If you prefer compiling manually:

javacc HL.jjt
javac *.java AST/*.java
java HL < your_input_file.hl

Replace your_input_file.hl with the actual HL source file.

Implementation Details

Abstract Syntax Tree (AST)

• Generated from HL.jjt.
• Key nodes include:
  • ASTvar_decl: Variable declarations
  • ASTfn_decl: Function definitions
  • ASTfn_call: Function calls
  • ASTAssign: Variable assignments
  • ASTPrint / ASTPrintln: Print operations
  • ASTIf, ASTFor, ASTWhile: Control structures
  • ASTsum, ASTmul, ASTdiv, ASTmod: Arithmetic operations
  • ASTcomparison: Comparisons and boolean operators
  • ASTset, ASTinterval: Set operations

Visitor Pattern in HLEval.java

• Each AST node has a corresponding visit method.
• Activation records (HLActivationRecord) manage variable scopes.
• Symbol tables (HLSymbTab) track variables and their values.

Usage Example

To run an HL program (e.g., example.hl):

java HL < example.hl

Ensure your test files are placed in the tests/ directory.

Debugging and Extensions

• Add debug print statements in HLEval.java for tracing.
• Modify HL.jjt to change the grammar, and update associated AST nodes accordingly.

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Enjoy exploring and extending the HL interpreter!