Pascal Interpreter

A fully-featured Pascal interpreter written in Python that supports variables, procedures, and arithmetic operations.

Features

• Lexical Analysis: Tokenizes Pascal source code
• Parsing: Builds an Abstract Syntax Tree (AST) from tokens
• Semantic Analysis: Validates variable declarations and scoping rules
• Interpretation: Executes the AST with call stack management

Supported Features

• Variable declarations (INTEGER and REAL types)
• Procedure definitions and calls
• Formal and actual parameters
• Nested scopes
• Arithmetic operations: +, -, *, /, DIV
• Unary operations: +, -
• Comments: { comment text }

Project Structure

• main.py - Entry point and command-line interface
• lexer.py - Tokenization module
• tokens.py - Token type definitions
• parser.py - Parser implementation
• ast_nodes.py - AST node classes
• semantic_analyzer.py - Semantic analysis and symbol table management
• interpreter.py - AST interpreter and execution engine
• errors.py - Error definitions
• demo.pas - Sample Pascal program

Usage

python main.py <pascal_file>

Options

• --scope - Print scope information during execution
• --stack - Print call stack during execution

Example

python main.py demo.pas

Sample Pascal Program

PROGRAM Demo;

VAR
    x, y: INTEGER;
    a: REAL;

PROCEDURE Add(num1, num2: INTEGER);
BEGIN
END;

BEGIN
    x := 10;
    y := 20;
    a := 5.5;
    Add(x, y)
END.