Haskell introduction

In this assignment, you will pick up the basics of Haskell. This will help you to understand and write the harder assignments later in the course.

Getting started

Make sure you completed the setup guide. Afterwards, set the following toolchain versions through the GHCup TUI.

• GHC 9.4.8
• HLS 2.9.0.0

Running and testing

You can build and test the code through stack. Make sure to be within the project folder before you run stack. One of the most useful commands throughout the course will be:

$ stack test

This will run the entire test infrastructure on your code. If all went well up to this point, this will give you a list of functions that failed their tests.

Individual tests may be run by matching on the test name. The following example will run the tests for head. If you want to run a group of test, you may match on the group name. To illustrate, you could replace head with List in the example to all run all the list tests.

$ stack test --ta="--match head"

There are many other ways to build and/or run your code. One recommended way would be to use GHCi. This is a Read-Eval-Print-Loop (REPL) that allows you to test smaller parts of your program. You could for example run a single function in your implementation via this command.

$ stack ghci

Here is a user-guide for GHCi. It is not all that difficult to use, but it is useful to know some of the commands like :r or :q. Note that running GHCi through stack already imports the current codebase into scope. This is practically always desireable, so we recommend running GHCi in this fashion instead of as a standalone program.

Assignment structure

Implement all function stubs found within the src folder of this project. A stub will have the following shape:

-- | Returns true if the passed list was empty
-- e.g. null [1, 2] = False
null :: [a] -> Bool
null = undefined

You will have to provide an implementation for this, e.g.

-- | Returns true if the passed list was empty
-- e.g. null [1, 2] = False
null :: [a] -> Bool
null [] = True
null _  = False

Notice how the comment above the stub provides you with an explanation of what the code is supposed to do, as well as an example case. Do make sure to read all the comments in a file. They provide useful insights, as well as occasionally ask you to implement functions in a specific way. Do not change the function signature of the stubs. This will generally make your program unable to compile!

The automatic tests that are ran by stack test will check whether your implementation is correct. These tests will also tell you in which order we think the assignment works best. Some tests may even depend on earlier pieces of your implementation in order to function. Hence, we strongly suggest to work in this order!

Grading

Your final grade corresponds directly to the one awarded to you by the test infrastructure. Do make sure your submission correctly executes on our online environment.

If there are issues with the submission system, don't panic! We will handle this on a case-by-case basis.

If your uploaded submission somehow fail tests that work locally, ping us and we will have a look!

If the online environment suddenly fails to work moments before the deadline, don't hesitate to send us your submission through different means (e.g. email).

Plagiarism

We have a strict zero tolerance policy against plagiarism. Sadly, we find cases every year... This is not fun for you, nor us. Please, refrain from copying and/or sharing your code with other students.

While we generally recommend our students to work via Git, do make sure to make your repository private! Sharing your code in this manner is sadly still plagiarism, even if unintentional.