On Thu, Nov 12, 2015 at 6:32 AM, David McBride <toad3k@gmail.com> wrote:

There was some real controversy over this change. People were strongly opposed to the change for exactly the reason you gave (among others), that it is hard for beginners. However, there was enough momentum that it went through, and now things like fmap and length work on a wide variety of data types. You can google ftp haskell controversy for more info.

Thanks, David. As far as instances of Functor, Applicative, and Monad, so far I've mostly used lists and Maybe. I've never taken specific advantage of Traversable.

Could you suggest a new type for me to explore? I mean something that could have instances in any of the above classes, one or all.

I only use Haskell for an occasional hobby project so despite having started five years ago, I consider myself a beginner. My project involves playing music by transforming a musical score into MIDI commands and sending them to a software synthesizer. As far as library types, I mostly use Map, lists, and Maybe. These are all I have needed to look for patterns in lists or Maps of notes. But I'm sure I'm missing out on something.