How to simplify nested map calls?

Question

Suppose I have a few nested functors, e.g. List[Option[Int]] and need to call the map of the most inner one.

Now I am using nested m

Answer 1

If you have a lot of nested functors and you don't want to flatten them (i.e. they're not monads or you don't want to use them as monads) - then lenses may help. There is quicklens implementation, which supports traversable lenses : http://www.warski.org/blog/2015/03/quicklens-traversing-options-and-lists/.

Example (sorry didn't try to compile it):

modify(opts)(_.each.each).using(_ + 1)

Anyway, you have to specify nesting level, but you don't have to nest functions here. And it's enough to specify it once, like (conceptual example, didn't check):

def md2[T]: (l: List[Option[T]]) => modify(l)(_.each.each)

md2[Int](opts).using(_ + 1)