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Comment by atemerev | Hacker News Reader

OOP hate is common these days, but I always has been an OOP enthusiast. I used to write in Smalltalk, I implemented a few metaobject protocols of my own, and I think OOP had deserves its success (unfortunately, C++/Java is not really OOP... However, some principles still apply).

So, when a language appeared to combine the best ideas from FP and OOP, I happily embraced it. And I want it to stay this way.

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Scala is a really great OO language, enabling very useful statically typed mixin compositions that you won't find in any other language. Uunfortunately, the vocal side of the community is very much anti OOP, so you don't hear about them much, but it is still there.

There are many excellent non-OO functional languages like Haskell, where functional concepts are mapped to much more elegant syntactic devices, having not much to do with OOP. There, ADTs are not expressed as "case classes", there's no need for implicits and coercions to enable type classes, and one can speak the word "monad" freely and bravely.

However, Scala is not Haskell. Scala's raison d'être is merging FP and OOP, and it excels at it. I'd like to leave it this way.

Sometimes you really need to drop into mutation of state in perf critical paths

There are great tools for that in both Scala and Haskell.

In Scala you can use var, which is easy.

In Haskell you can write your algorithm using ST and then use it as a pure function by means of runST. The type system guarantees that all such state is local to the invocation.

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