So ignoring Java and concentrating entirely on expressiveness & ignoring readability, maintainability, etc... It seems like Collections are the entire kitchen sink of algorithms that map across iterable content. How is that better than more precise types (functors, monoids, monads, foldables)?

For example: what is the benefit of reducing these data structures (and associated algorithms which operate on them) to more generic versions?

> There's one additional cool feature of Scala collections which I haven't touched on yet: transformations can result in collections that are different from the original collection type, and the most specific collection that is compatible is used. What does that mean? Say I map a TreeSet from an ordered element type to an unordered type. The result type can no longer be stored in a TreeSet, so you get a more generic Set collection instead. I'm curious what it would take to implement this in Haskell.

While I agree that this is "cool" that you can do that, I really don't see the use of it except when sketching out ideas when you're not sure what kind of data flow you want yet... but that seems like a problem with designing the program and should be avoided.