100 Haskell Interview Questions and Answers
Programming Languages · 100 questions, each with a full written answer — free, no sign-up.
Reading is step one. Saying it out loud is the interview.
Our AI interviewer calls your phone and runs a realistic Haskell interview — then scores it.
📞 Practice Haskell — free 15 min
📕 Buy this interview preparation book: 100 Haskell questions & answers — PDF + EPUB for $5
Basic
- What is Haskell and what are its main features?
- What is functional programming? How does it differ from imperative programming?
- Can you explain what is a pure function in Haskell? Give an example.?
- How are variables declared and assigned in Haskell?
- How does Haskell handle errors and exceptions?
- What are higher order functions? Can you provide an example in Haskell?
- What is a monad in Haskell?
- Explain the concept of immutability in Haskell. Why is it important in functional programming?
- How are lists defined in Haskell? Provide an example.?
- What is type inference in Haskell? How does it work?
- What is lazy evaluation in Haskell? Give an example.?
- How does Haskell handle I/O operations, given its pure functional nature?
- Explain the concept of currying in Haskell with an example.?
- What are pattern matching and guards in Haskell? Can you write a simple function using these?
- What is a type class in Haskell? Give an example.?
- How does garbage collection work in Haskell?
- What is the difference between let and where in Haskell?
- Explain how you would create and use a tuple in Haskell.?
- What are the basic data types in Haskell?
- Can you write a simple recursive function in Haskell?
Intermediate
- Can you explain the concept of Functor in Haskell? How is it different from a Monad?
- How does Haskell’s type system improve code safety?
- How do you handle state and side effects in Haskell?
- How do you handle concurrency in Haskell? Can you mention some libraries that are used for this purpose?
- How do you typically structure a medium to large-scale Haskell project?
- What is a monad transformer? Provide an example where it might be useful.?
- What are algebraic data types in Haskell? How are they used?
- How can you generate a list of all the prime numbers in Haskell?
- What is the purpose of the main function in Haskell?
- What are some common Haskell libraries you have used, and what did you use them for?
- Explain how to do error handling in Haskell with the Either type.?
- How does Haskell’s garbage collector handle cyclic references?
- Can you describe a situation where you would use seq function in Haskell?
- How do you work with databases in Haskell? Can you mention a few libraries?
- What is a type variable in Haskell? How is it different from a concrete type?
- Explain the use of the IO monad and how it enables Haskell to interact with the outside world.?
- How can you use the State monad in Haskell to maintain state?
- Can you explain the concept of partial application in Haskell? Provide an example.?
- How can you test Haskell code? Are there any specific libraries you prefer for this purpose?
- Explain how the QuickCheck library works in Haskell. How does it help in testing?
Advanced
- Can you explain the concept of "Type-Level Programming" in Haskell? Give some examples of its usage.?
- How does the GHC (Glasgow Haskell Compiler) optimize the Haskell code?
- What are some ways to deal with the "diamond dependency problem" in Haskell?
- How does Haskell’s type system handle polymorphism?
- Can you explain the differences between ’foldl’, ’foldr’, and ’foldl1’ functions in Haskell?
- How do you manage memory usage in a large Haskell application?
- How does Software Transactional Memory (STM) work in Haskell? Provide an example.?
- How can lenses be used in Haskell? Give a practical example.?
- What is the role of the "GHCi" in Haskell development?
- Can you explain the concept of "Monadic Parsing" in Haskell? Give an example.?
- What are the differences between ’newtype’ and ’data’ in Haskell?
- Explain the concept of type families and how they are used in Haskell.?
- How do you optimize recursive functions in Haskell? Explain with an example.?
- How do you handle real-time data streams in Haskell? Are there specific libraries you would use for this?
- Can you explain the differences between ’lazy’ and ’strict’ in Haskell?
- How do you handle foreign function interface (FFI) in Haskell? Give an example.?
- How do you profile and debug a Haskell program?
- Describe a situation where you would use the ’Reader’ monad in Haskell.?
- What are "GADTs" in Haskell and what are some use-cases for them?
- How do you manage package dependencies in a Haskell project?
Expert
- How would you design a Haskell program for high performance and concurrency? What libraries or techniques would you use?
- Explain the "Space Leak" problem in Haskell. How can you avoid it?
- How does Template Haskell work, and what are some of its uses?
- Can you describe a real-world system you’ve built in Haskell? What were the biggest challenges and how did you address them?
- What is the role of "Existential Quantification" in Haskell?
- How do you implement and maintain a Domain Specific Language (DSL) in Haskell?
- How would you implement a REST API server in Haskell? What libraries would you use?
- Can you explain the concept of "Rank-N Types" in Haskell? Give an example.?
- What is the difference between ’IORef’, ’MVar’, and ’TVar’? When would you use each?
- How do you handle mutable state in Haskell? Discuss some techniques and libraries.?
- Can you describe a use case for "Dependent Types" in Haskell?
- What is the role of "Phantom Types" in Haskell and what problems do they solve?
- Can you explain the difference between ’Conduit’, ’Pipes’ and ’Streaming’ libraries in Haskell? When would you use each?
- How would you use the ’Free Monad’ in Haskell? Discuss a real-world example.?
- How would you approach debugging performance issues in a Haskell application?
- How would you handle interoperation between Haskell and other languages?
- How do you design and implement testing for a large Haskell application? What libraries and techniques do you use?
- Can you explain the "Church Encoding" concept in Haskell?
- How would you use "Type Families" in a large Haskell project?
- What are some of the trade-offs of using Haskell in a large-scale production environment?
Guru
- How would you design a distributed system in Haskell? What libraries or frameworks would you use?
- Can you explain the role of "Linear Types" in Haskell and provide an example of their use?
- What are some limitations of Haskell’s type system, and how have you worked around these in your own projects?
- How would you optimize a Haskell program for a high-throughput, low-latency scenario?
- Can you discuss a time when you had to make a significant architectural decision in a Haskell project? What factors influenced your decision and what was the outcome?
- How does Haskell’s runtime system work? Explain the concepts of Thunks and the Spine.?
- How can Haskell support the development of a microservices architecture? What challenges might you encounter?
- Discuss the concept of "Symbolic Computation" in Haskell. How can it be utilized in real-world applications?
- How would you approach building a machine learning model in Haskell? What libraries or tools would you use?
- How can the "Arrow" concept in Haskell be used in practice? Provide an example.?
- Can you explain the advanced usages of "Monadic Effects" in Haskell?
- How do you approach code optimization in Haskell at scale?
- What are your strategies for ensuring Haskell code is safe from common security vulnerabilities?
- How would you use Haskell in a big data context? Discuss the libraries and paradigms you would use.?
- Discuss the concept of "Continuation-Passing Style" in Haskell. When is it used?
- How have you used "Category Theory" concepts to solve problems in Haskell?
- What’s your approach to build and manage a team of Haskell developers, especially considering Haskell is less mainstream than some other languages?
- Discuss a time when you used Haskell’s strong type system to solve a complex problem.?
- How would you use "Monad Transformers" in a large codebase? Discuss some challenges and how to overcome them.?
- Can you discuss the potential challenges and solutions when interfacing Haskell with other languages in a polyglot system?
📕 Buy this interview preparation book: 100 Haskell questions & answers — PDF + EPUB for $5
Reading is step one. Saying it out loud is the interview.
Our AI interviewer calls your phone and runs a realistic Haskell interview — then scores it.
📞 Practice Haskell — free 15 min