Real World Haskell

What Hacker News says

1. kreyenborgiOct 2026
   https://wiki.haskell.org/index.php?title=Real_World_Haskell was a great book, but it is nearly 20 years old. Haskell has changed some. An update would be nice. It seems jaror has begun the work.
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2. argiopetechNov 2025
   I typically recommend LYAH (https://learnyouahaskell.github.io/chapters.html), followed by Real World Haskell (already mentioned).
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3. WorldMakerJun 2025
   I loved the book "Real World Haskell" [1] when it first came out in 2008. It feels like a shame it hasn't aged well and there hasn't been an updated edition since then. Especially because it was focused on things like "here's how you build example web services" as a good place to discuss everything else by having the end goal of the book's "narrative" structure be real world things you might build. It may still help to glance at a little, but things have advanced so much in the decade and a half since the book was written it is hard to recommend, but it still feels like there should be a book like it updated for current day to be out there to more heartily recommend. If there is one I don't know of it, but I haven't followed Haskell as much as I'd like in my professional career.

   [1] https://book.realworldhaskell.org/

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4. wavemodeMar 2025
   > Yes, I really need a real word Haskell project simple enough to understand all the math concept

   There actually is a book with precisely that title, which provides what you're asking for: https://book.realworldhaskell.org/

   > Like, I don't know when to implement the Monad type-class to my domain data types

   A concrete type (such as your Tweet type) can't be a Monad. Monad is implemented on generic types (think: `MyType a`, where `a` can be filled in with a concrete type to produce e.g. `MyType Int` or `MyType String`).

   Most monads are data structures like list `[a]` or structures which provide context to computations like `State s a` or `Reader r a`

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5. setoptSep 2024
   I didn’t play with this myself, but I’ve heard good things about writing parsers in Haskell (e.g. the Parsec library and friends). Hell, even Pandoc is written in Haskell and that’s arguably the king of document parsers. So that could be one area. I also heard cool things about QuickCheck, which I think is the inspiration for Hypothesis in the Python ecosystem, if you want to explore more how to do testing. Perhaps the “Real World Haskell” book might be a good fit to see other possible projects.

   Except the obvious functional programming concepts, one thing I enjoyed exploring in Haskell was “infinite data structures” and “lazy evaluation” – like how you could provide a recursion relation to define an infinite list of numbers, but only the finite elements in the list you ask to print are actually calculated behind the scenes. This “lazy evaluation” can be used to build algorithms that would be completely unreasonable in any other language.

   I also liked how easy it is to define new data structures. Like implementing a minimal tree data structure can be done in literally one line of code, which is just ridiculous compared to most languages that I’ve tried.

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6. tiberius_pJul 2024
   Real World Haskell was pretty good last time I read it. It has lots of concrete code examples that you can use in real world applications. It won't bore you to death with abstract theory and instead it will blend it with real world problems and make learning both fun and useful at the same time.
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