I really like the amount of nonsense.)

It begins with head is a mistake! It should not be in the Prelude. Other partial Prelude functions you should almost never use include tail, init, last, and (!!). From this point on, using one of these functions on a homework assignment will lose style points!

And here is a proposal:

  data NonEmptyList a = NEL a [a]

  nelToList :: NonEmptyList a -> [a]
  nelToList (NEL x xs) = x:xs

  listToNel :: [a] -> Maybe (NonEmptyList a)
  listToNel []     = Nothing
  listToNel (x:xs) = Just $ NEL x xs

  headNEL :: NonEmptyList a -> a
  headNEL (NEL a _) = a

  tailNEL :: NonEmptyList a -> [a]
  tailNEL (NEL _ as) = as

Dear sirs, a List is a recursive data structure by definition. Non-recursive List is an unimaginable nonsense. What was made here with a name of safe(!) NonEmptyList is some ugly Pair with lots of syntactic noise.

How could you get the last element from your NonEmptyList? How could you tell how many elements in it?)

But, of course, never ever use these ugly unsafe lists - they might be empty! Use safe NonEmptyList because in Haskell everything is safe. And never try to think what the fuck you are reading.