This is actually a very good comment. Haskell has had these features since early ~2000s and it was a major competitive advantage in the language space, but today I would argue that if you're using a modern language then they don't stand out as much. Nevertheless, not all popular languages provide all the above mentioned features and in case they implement them it's usually in a compromised fashion. For example, nullable types are still an open issue in Java, while C# and Typescript provide easy ways to circumvent them, a lot of times by accident (the main issue is that they're mostly annotations, not runtime checks).
On the other hand, you mention several features which Haskell provides, usually through libraries that can only be implemented due to the features provided by the base language:
- Refinement types [1] allow to add runtime invariants to existing types in an ergonomic fashion, or you can go even further and use something like LiquidHaskell[2] to enforce properties at compile time.
- For multithreaded programs, the existence of STM[3] allows to to write mutable variables which are safe to use across threads. Very few languages offer something like this.
- For structural dependencies, you can apply the techniques of "ghost of departed proofs"[4]. Personally I don't like to go that route since programming becomes an act of "proving" rather than "doing" but I appreciate the fact that you can encode it if you want/need to.
- Metaprogramming in Haskell is not as ergonomic as in a LISP yet you have the full access to the language through TemplateHaskell[5]. A more constrained form is available as QuasiQuotations that allow you, for example to write a regex[6] string and have it compiled alongside the rest of the code.
There are other features that I personally think are still far ahead from the competition, like lenses[7] to traverse nested data, the async[8] package for ergonomic concurrent programs, effect systems[9] for more granular dependency injection, immutability by default to avoid corrupting state, full type inference, top level functions and values (I can't believe the amount of times I find myself missing them in OOP languages like Java and C#), among others.
Thank you, I appreciate that. And that you took the time to write such a complete response.
At the end of the day, Haskell is just way too slow (at runtime) for me to consider using, so debating that these features satisfy my requirements is purely an academic exercise. One which I don't have much interest in doing.
I am glad to hear that you seem to enjoy using Haskell, and I hope it continues to bring you joy :)
On the other hand, you mention several features which Haskell provides, usually through libraries that can only be implemented due to the features provided by the base language:
- Refinement types [1] allow to add runtime invariants to existing types in an ergonomic fashion, or you can go even further and use something like LiquidHaskell[2] to enforce properties at compile time.
- For multithreaded programs, the existence of STM[3] allows to to write mutable variables which are safe to use across threads. Very few languages offer something like this.
- For structural dependencies, you can apply the techniques of "ghost of departed proofs"[4]. Personally I don't like to go that route since programming becomes an act of "proving" rather than "doing" but I appreciate the fact that you can encode it if you want/need to.
- Metaprogramming in Haskell is not as ergonomic as in a LISP yet you have the full access to the language through TemplateHaskell[5]. A more constrained form is available as QuasiQuotations that allow you, for example to write a regex[6] string and have it compiled alongside the rest of the code.
There are other features that I personally think are still far ahead from the competition, like lenses[7] to traverse nested data, the async[8] package for ergonomic concurrent programs, effect systems[9] for more granular dependency injection, immutability by default to avoid corrupting state, full type inference, top level functions and values (I can't believe the amount of times I find myself missing them in OOP languages like Java and C#), among others.
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[1] https://hackage.haskell.org/package/refined [2] https://ucsd-progsys.github.io/liquidhaskell/ [3] https://hackage.haskell.org/package/stm [4] https://hackage.haskell.org/package/gdp [5] https://serokell.io/blog/introduction-to-template-haskell [6] https://hackage.haskell.org/package/regexqq [7] https://hackage.haskell.org/package/lens [8] https://hackage.haskell.org/package/async [9] https://hackage.haskell.org/package/effectful