Helix Interpreter

Technologies Used

Overview

The “Helix Interpreter” project is a Python-based interpreter for a custom language, demonstrating fundamental compiler design principles including lexical analysis, parsing, abstract syntax tree (AST) traversal, and semantic evaluation.

Architecture and Structure

The project follows a modular, component-based architecture:

• grammar/: Contains Helix.g4, the core ANTLR grammar file defining the language’s lexical tokens and syntactic rules. ANTLR generates the Lexer and Parser from this file.
• builtins/: Defines the language’s standard library functions (like output <<) and built-in data types (INTEGER, DOUBLE, STRING, BOOL).
• core/: Houses the main interpretation logic.
  • evaluator.py: Inherits from ANTLR’s HelixVisitor and implements the Visitor design pattern. It traverses the AST generated by the parser and executes the code.
  • environment.py & environment_stack.py: These classes manage variable scopes. An Environment object represents a single scope (like a function or loop body), and the EnvironmentStack manages a stack of these objects to handle nested scopes correctly.
• runtime/: Orchestrates the execution. interpreter.py coordinates the parsing and evaluation process, while runner.py provides the command-line interface.

Key Functionality

• Syntactic Analysis: Uses ANTLR to parse Helix scripts, generating a parse tree according to the rules in Helix.g4.
• Semantic Evaluation: The Evaluator traverses the parse tree, executing statements and evaluating expressions recursively.
• Type System: Supports integer, double, string, and bool with type checking during operations and comparisons to prevent invalid operations.
• Scope Management: Uses an environment stack to handle nested lexical scopes, correctly resolving variable lookups and assignments within blocks like for or if.
• Symbol Table Generation: After execution, it outputs a RES_SYM.txt file listing all identifiers, their final types, values, and scopes.