EECS4302 ANTLR4 Parser Generator Tutorial: Part 4

Step-by-Step Tutorial:

1. Understanding the Hierarchy:

   • In the previous tutorial, the hierarchy of visitor classes was discussed, highlighting the importance of the labels added to the input grammar file.

2. Creating Visitor Classes:

   • Create two visitor classes, AntlrToExpression and AntlrToProgram, to convert parse tree nodes into expression objects in the expression package.

3. Implementing AntlrToExpression Class:

   • In Eclipse, create a new Java class named AntlrToExpression under the expression package.
   • Extend the class with ExpressionBaseVisitor and instantiate it with Expression.
   • Override the necessary visit methods for different node types like number, variable, decoration, multiplication, and addition.

4. Implementing AntlrToProgram Class:

   • Create another Java class named AntlrToProgram under the expression package.
   • Extend the class with ExpressionBaseVisitor and instantiate it with Program.
   • Override the visitProgram method to handle the program node and recursively visit its children to convert them into expression objects.

5. Handling Semantic Errors:

   • Maintain a list to store variables declared in the program to check for semantic errors like variable duplication and undeclared variables.
   • Report semantic errors by adding messages to the semantic errors list when necessary.

6. Completing the Implementation:

   • Ensure proper error handling and reporting for semantic errors in variable declarations and references.
   • Recursively visit child nodes to convert them into expression objects, ensuring correct conversion and error checking.

7. Testing and Finalization:

   • Test the implemented classes by running the visitor methods on sample input parse trees to verify correct conversion to expression objects.
   • Verify that semantic errors are properly reported and handled during the conversion process.

8. Final Steps:

   • Ensure all necessary methods are correctly overridden in the visitor classes for handling different node types.
   • Review the implemented code for any errors or missing functionalities before proceeding to integrate the visitor classes into the main application program.

By following these steps, you can successfully implement the visitor classes to convert parse tree nodes into expression objects while handling semantic errors in variable declarations and references.