Homework 9🔗

Last updated: Tue, 5 Nov 2024 19:48:45 -0500

Out: Mon Nov 04, 2024, 12pm (noon) EST

Due: Mon Nov 11, 2024, 12pm (noon) EST

Overview🔗

In this assignment, we will begin a deeper study of "high-level languages" by implementing (a basic) one. Fortunately, using the The Design Recipe, this seemingly difficult task can be completed using the exact same methods as previous assignments.

This hw will be graded accordingly:

Setup🔗

Create a new repository for this assignment by going to the CS450 Fall 2024 GitHub Organization and clicking "New".

Note: The CS450 Fall 2024 GitHub Organization must be the owner of the repository. Do not create the repository in your own account.

When done click "Create repository".

Tasks🔗

Reading

• Review the The Design Recipe section of the course website (topics that will be covered in future lectures are marked as such).

Notes and Reminders

• All code you write must now follow the The Design Recipe. (Just submitting code is no longer sufficient.)

• Signatures should use define/contract and the predicates defined in the Data Design Recipe step. You may need more more sophisticated contract constructors such as listof for this assignment.

• For Examples and Tests, do not use check-expect from the Beginning Student Language (even though the textbook says to). Instead, use check-equal? or other testing forms from rackunit.

• Examples for a function definition should come right after the define. But Tests should be put into the test-suite in tests.rkt. Try to think about corner cases and code coverage.

• Also, remember that Racket Style and The Design Recipe reserves certain language features only for specific scenarios. For example, set! and other "imperative" features are not allowed ever. Conditionals such as cond should only be used with enumeration or itemization Data Definitions.

• The submitted program must be only a series of defines (both constants and function definitions are allowed) and tests/examples. Do not run any other code, i.e., do not automatically start big-bang! Not following this this will result in GradeScope errors and point deductions.

• NEW You may find the "Syntactic Test Coverage" feature in DrRacket useful. At minimum, one-hundred percent of your code should be run (if not tested) before submission.

• The main code should go in a file named hw9.rkt and tests should go in a tests.rkt file of the appropriate format.

  In this assignment, each function should have at minimum of one (meaningful) Example and two Tests (that are not the same as the example).

Programming

Submit the in-class programming task(s) from Lecture 17 and Lecture 18.

Specifically, create the "CS450 Lang" programming language by implementing the following functions.

• parse : takes a 450LangExpr (abbreviated Expr) "program" and produces a 450LangAST abstract syntax tree (abbreviated AST) data structure.

• run : takes a 450LangAST tree and "runs" it, to produce a 450LangResult "result" (abbreviated Result)

  As mentioned in lecture, the semantics of the language, e.g., "adding" strings, should follow JavaScript semantics. When in doubt, we will use the repljs.com evaluator as the official specification for the behavior of "CS450 Lang" programs.

• NaN? : returns true if the result is a NaN result

For reference, here are the Data Definitions that we are using (as given in class):

• A 450LangExpr (Expr for short) is one of:

  • Number

  • String

  • (list ’+ Expr Expr)

  • (list ’- Expr Expr)

  Interpretation: represents the surface-level syntax of CS450Lang programs

• A 450LangAST (AST for short) is one of:

  • (num Number)

  • (str String)

  • (add AST AST)

  • (sub AST AST)

  Interpretation: represents an abstract syntax tree data structure that is produced from parsing the surface program

• A 450LangResult (Result for short) is one of:

  • Number

  • String

  • NaN

  Interpretation: possible results after running a CS450Lang program

Before Submitting🔗

Testing

Style

All code should follow proper Racket Style.

Also, the repository itself must follow proper style. Specifically, it must have appropriate commit messages. See How to Write a Git Commit Message if you are unsure how to write a commit message.

Files

A submission must have the following files in the repository root:

• hw9.rkt: Contains the hw solution code.

  All defines should use the name specified in the exercise (ask if you are unsure) and should be provided.

  The easiest (but not always the most readable) way to ensure all necessary definitions are provided is to (initially) put as the second line in the file:

  (provide (all-defined-out))

  This automatically provides all definitions in the file. (The first line should be #lang racket)

• tests.rkt: This file should require hw9.rkt and define tests for it.

  Specifically, it should define a rackunit test-suite which contains sufficient rackunit test cases (e.g., check-equal?, etc.) for each defined function.

• README.md: Contains the required README information, including the GitHub repo url.

Submitting🔗

When you are done, submit your work to Gradescope hw9. You must use the "GitHub" Submission Method and select your hw<X>-<LASTNAME>-<FIRSTNAME> repository.

Note that this is the only acceptable way to submit homework in this course. (Do not manually upload files and do not email files to the course staff. Homework submitted via any unapproved methods will not be graded.)