[chiurox]

How about WhatsApp's backend being extremely scalable because it was written in Erlang from the start? Or even Twitter that rewrote much of their backend in Scala to deal with scaling issues (I'm not saying that Rails isn't scalable, I don't want to start a war over this issue; the important thing is they saw a problem and solved it) while contributing many many open sourced libraries for our use?

Foursquare uses Scala extensively. LinkedIn is using Scala extensively for its new projects. The commercial and successful use cases for Scala are widespread at this point. For Haskell and OCaml it's going to take a while.

[pron]

Well, when people say FP they mean different things. The Erlang/Clojure kind bears little resemblance to the Haskell/scalaz sort discussed in the article. Neither does most of the Scala code written at Twitter (which is mostly OO with a sprinkling of functional).

[tel]

That's hardly true. Erlang's event loops are based on a very similar kind of state encapsulation as Haskell's state monad. Really Erlang is littered with explicit monadic patterns but lacks a good system for abstracting over those patterns so you just call them "OTP" instead of a monad.

[virtualwhys]

It says a lot about the scale of adoption the big language players have that despite the aforementioned inroads into the enterprise that Scala has made, it is still very much a niche language; Haskell at this point in time, even more so.

Am curious to see how Scala 3/Dotty backed Scala works out. Enabling better tooling and faster build times via a generally less kitchen sink-y/more regular language should bring Scala adoption to new levels. Dotty is under active development, even saw a Github issue talking about the migration tool[1]. It's going to happen, just a matter of when.

[1] https://github.com/lampepfl/dotty/issues/129