Haskell Interview Questions for Developers

A purely functional programming language, Haskell maintains popular usage due to its strong static typing and type inference, its use of lazy evaluation for more efficient code, and its use of algebraic data types and pattern matching.

Haskell was first conceived in the late 1980s during a series of meetings among researchers in functional programming languages. The goal was to create a standardized, open-source, purely functional programming language.

https://doi.org/10.1145/1238844.1238856

Our team has developed practical coding assignments and interview questions tailored to assess developers’ Haskell skills during coding interviews. Additionally, we have compiled a set of best practices to ensure your interview questions accurately evaluate the candidates’ proficiency in Haskell.

Haskell example question

Help us design a parking lot

Hey candidate! Welcome to your interview. Boilerplate is provided. Feel free to change the code as you see fit. To run the code at any time, please hit the run button located in the top left corner.

Goals: Design a parking lot using object-oriented principles

Here are a few methods that you should be able to run:

• Tell us how many spots are remaining
• Tell us how many total spots are in the parking lot
• Tell us when the parking lot is full
• Tell us when the parking lot is empty
• Tell us when certain spots are full e.g. when all motorcycle spots are taken
• Tell us how many spots vans are taking up

Assumptions:

• The parking lot can hold motorcycles, cars and vans
• The parking lot has motorcycle spots, car spots and large spots
• A motorcycle can park in any spot
• A car can park in a single compact spot, or a regular spot
• A van can park, but it will take up 3 regular spots
• These are just a few assumptions. Feel free to ask your interviewer about more assumptions as needed

Best interview practices for Haskell roles

To conduct successful Haskell interviews, it is important to consider various factors, such as the candidate’s background and the specific engineering role. To ensure a positive interview experience, we recommend adopting the following best practices:

• Craft technical questions that reflect real-world business scenarios within your organization. This approach will effectively engage the candidate and help assess their compatibility with your team.
• Create a collaborative environment by inviting candidates to ask questions during the interview.
• It’s also helpful if candidates can demonstrate knowledge of useful Haskell libraries like Cabal, Stack, and Hackage.

In addition, adhering to standard interview practices is vital when conducting Haskell interviews. This involves adjusting the question difficulty to match the candidate’s abilities, providing timely updates on their application status, and giving them the opportunity to ask about the evaluation process and collaboration with you and your team.