I agree with you, i love haskell’s syntax and function first m style, guards, do’s, types first ..
Id call a maybe monad a “safe container type” rather than a monad, where applicatives id call “mappables” ... maybe should write a book about it someday. I understand how criticism is tiring as-well, math people mean well and i honestly don't mean ti take away their toy.
I am objecting to obscurantist presentation. It doesn't have to be THAT opaque for such a simple modulo arithmetic problem.
I object to the implementation given in the article. It's ugly and brittle because of how specific it is.