5 Simple Macros
Due: Wednesday, January 29, 11:59pm.
Starter code: hw5-starter.rkt.
Implement the macros sketched in the starter file. For each macro:
Before implementing the transformation, write example expanded code for the provided example use of the macro. We’ll look for these examples in the comment above each macro definition.
Implement the transformer using syntax-parse. The pattern matches you perform using syntax-parse and recursive uses of the macro should follow the structure of the provided grammar, except for the cases macro as discussed below.
Write test cases of the form’s behavior that cover the code generated by each branch of the macro, using rackunit. Put these in a module+ test submodule just below each macro definition. DrRacket will run the test submodule when you run the file in the IDE, or you can run it from the command line with raco test.
For cases, you will need to transform the grammar so that it has one top-level option, like we did in class for cond. Write the transformed grammar as part of the comment above cases in your submission.
You should write the patterns for your macro such that expansion raises a syntax error for any inputs that do not follow the grammar. Improving the quality of the resulting error messages and unit testing error behaviors is extra credit.
5.1 Extra credit
Use features of syntax-parse such as define-syntax-class, existing syntax classes such as id and expr/c, and ~! to provide better error messages than the defaults when the user’s code does not match the expected structure. These were not fully covered in class, so this will require some extra reading of the documentation.
Write test cases using convert-compile-time-error that demonstrate these improved errors. Include a comment with the test case describing the improvement.
Submission
Submit to Gradescope, in a group submission with your partner: https://www.gradescope.com/courses/941020/assignments/5652889/
Upload your submission as a single hw5.rkt file.