> The biggest FP project I was aware of was Twitter using Scala and they ended up completely backing away from it. Yikes.
You must be joking, Twitter is far and away the largest Scala shop in the world.
Presumably you're mixing up LinkedIn's recent move from Scala to Java. An important caveat is that they're still using the Play framework (Typesafe product), just now in Java instead of Scala.
It's unfortunate that Play serves two masters (i.e. Scala and Java), but industry demands it -- the argument that FP is the one true way goes out the window in face of current reality: enterprise by and large will go with mature tooling and cheap developers in a large-team-friendly language like Java over a paradigm shifting FP language like Scala, Clojure, or Haskell.
You must be joking, Twitter is far and away the largest Scala shop in the world.
Presumably you're mixing up LinkedIn's recent move from Scala to Java. An important caveat is that they're still using the Play framework (Typesafe product), just now in Java instead of Scala.
It's unfortunate that Play serves two masters (i.e. Scala and Java), but industry demands it -- the argument that FP is the one true way goes out the window in face of current reality: enterprise by and large will go with mature tooling and cheap developers in a large-team-friendly language like Java over a paradigm shifting FP language like Scala, Clojure, or Haskell.