Haskell - Capitalize all letters in a list [String] with toUpper

Question

I have a list [String] the task ist to remove those elements in the list, which have \"q\" or \"p\" and then capitalize all letters in the list with toUpper.

What I

Answer 1

I know, that toUpper in this line of code gets a list as value and therefore it can't work, but know how to go a level down into the list and the apply map toUpper.

Use (map . map) instead of map.

n.b. (map . map) toUpper is the same as map (map toUpper) as suggested by the other answers. I mention it because, personally, I find it clearer: it looks more like it is going down two levels to apply toUpper. (You may not be familiar with the function composition operator (.), look it up or ask about it if you need to.)

Other functions with a similar type ((a -> b) -> something a -> something b), such as fmap, Data.Map.map, first and second, can be combined with each other and with map in a similar way.

Perhaps you don't find (map . map) toUpper clearer than map (map toUpper); fair enough.