21 Homework 14A

Due:

Tuesday, 4/16 at 9PM

This assignment may be done with an approved PARTNER.

There is no starter file, since you’ll be writing in whatever language you chose in Homework 10A.

Please submit your homework to the HW14A assignment on Gradescope.

21.1 Revisiting Your Choice

In this assignment, you will return the the Property Based Testing library you identified and wrote a memo about in Homework 10A. Specifically, we want you to solve several problems using it.

21.2 Problem 1

Test out your property-based testing library by implementing the following functionality in your language, writing property-based tests, and running them:

Show that sorting a collection (array, list, etc) does not change the size of the collection.

Write code that adds an element to a collection (array, list, etc), if it doesn’t already exist in it, and show that it does not decrease the size of the collection.

21.3 Problem 2

In this problem, we want you to use an existing JSON serialization/deserialization library (if your language does not have one, you can of course implement it, but that’s not our intention).

First, you need to define a data structure (in your programming language) that represents a map from student ids (as strings) to structures representing students (with a name, list of interests, and address). This data structure is part of a hypothetical application for matching students with people who live near them and have similar interests, the rest of the application will not be implemented!

Now, you should write code that turns that data structure into JSON (using whatever functionality is available in your language’s JSON library), and separate code that does the reverse. This would be used to either store the data, or send it over the network.

Now, write property-based tests that show that for random examples of your data structure, the serialization and deserialization functions are inverses of each other; i.e., that deserialize(serialize(x)) = x for all x.

21.4 Problem 3

In this problem, first define a native data type for a color, which should be able to represent colors in the following three ways:

Named colors (Red, Green, Blue, etc: how many is up to you, but a finite number)

RGB colors (three numbers, 0 to 255, that represent the amount of Red, Green, or Blue in the color)

CMYK (four numbers, 0 to 255, that represent how much Cyan, Magenta, Yellow, and Black, in the color)

Now, write code that turns your color into a "packed" representation as an array (or list) of numbers. You are welcome to choose any representation as you like, but we’d suggest using the first number as a "tag" that indicates which possibility you are in.

Next, write code that takes a "packed" representation as an array (or list) of numbers, and convert it back into the native color data structure.

Finally, write property based tests that show that for random examples of your color, the "unpacking" and "packing" functions are inverses of each other; i.e., that unpack(pack(x)) = x for all x. You should also show that for any array (or list) of numbers, the "unpacking" function either gives a sensible error, or returns a color that, when "packed", gives the same array (or list) of numbers.