Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
You can send code in code blocks by using three backticks, the code, and then three backticks or use something such as https://topaz.github.io/paste/ if you prefer sending it through a URL
. means function composition in Haskell. (f .) . (+) is just an obscure way to write \x y -> f (x + y). It's not recommended to use this point-free style in production code, but it is sometimes fun to experiment with for challenges like this.