CASS Parsing and AST Representation

This repository implements a CASS (Context Aware Semantics Structure) parser using ANTLR4. It consists of the following key components:

• CASS.g4: Defines the grammar for parsing C-like syntax using ANTLR4.
• MyCASSVisitor.py: Implements a visitor pattern to generate and traverse the parse tree.
• DriverCASS.py: Acts as the main entry point for parsing and processing CASS input.
• CASSNode.py: Defines the Cass node structure and serialization utilities.

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CASS Grammar (CASS.g4)

This file defines the ANTLR4 grammar for parsing a subset of C-like syntax, including:

• Function definitions
• Statements (if, while, for, return, switch, case etc.)
• Expressions (arithmetic, logical, assignment)
• Parenthesized expressions
• Function calls
• Variable declarations
• Arrays, lists and pointers

The grammar ensures a well-structured parse tree that is then visited by MyCASSVisitor.py.

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CASS Visitor (MyCASSVisitor.py)

This module implements the visitor pattern for processing all parsed components using the grammar file. Key functionalities include:

• Constructing CASSNode's
• Labeling for nodes, including variable declarations, expressions, and operators.
• Child management, allowing hierarchical tree representation.
• Distinguishing between local and global variables.
• Recognizing parenthesized expressions and operator precedence.
• Properly formatting function calls and argument lists. ...

The visitor ensures a structured transformation of the parsed syntax into an intermediate AST representation.

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Driver (DriverCASS.py)

The driver script serves as the main entry point for executing the CASS parsing pipeline. It:

• Loads and compiles the grammar using ANTLR4.
• Instantiates the MyCASSVisitor to process the parse tree.
• Generates and prints the corresponding AST structure.
• Serializes the AST into the expected CASS string format.

This script acts as the core engine for testing and processing input files.

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Node Representation (CASSNode.py)

This file defines the CassNode class, which represents nodes in our Cass tree. It includes:

• Serialization to CASS format, ensuring proper formatting for output.
• GraphViz DOT export, enabling visualization of the tree structure.

The CassNode class provides the foundational structure for storing and manipulating AST representations.

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How to Run

Ensure you have ANTLR4 installed and available in your environment. To run the parser:

java -jar "antlr-4.13.2-complete.jar" -Dlanguage=Python3 -visitor CASS.g4
python DriverCASS.py <input_file.c>   

Our Jupyter Notebook

We also created a Jupyter Notebook Execution.ipynb with integrated vectorization and similarity score calculation using a pretrained graph neural network provided by the authors of the MISIM paper. In order to run it, it might be necessary to install some packages.