Oh, I am lost now - for now anyway.
I am attempting to do next exercise in the book to define reverse function
using primitive recursion and pattern matching on lists. But getting stack
because when i con in front of xs (xs:x) i get en error, which i thought i
would be getting anyway. I tried to define a helper function and cons there
in front of xs and i get type errors again.

I know these are easy and boring questions but i would appreciate a hint.

Thank you

Let's look at the type of the cons operator:

Prelude> :t (:)
(:) :: a -> [a] -> [a]

That is, it takes an element of any type (here represented by 'a'), and a list of the same type, and produces a list. So (xs:x) does not make sense, assuming that xs is a list and x has the same type as an element of xs; cons expects an element followed by a list, and you are giving it a list followed by an element. If you want to append an element onto the end of a list you can do

xs ++ [x]

++ is the list append operator, so this says "make x into a list with one element, and append it onto the end of the list xs".

Does that help? It's hard to help without seeing any code or the specific errors you are seeing, but hopefully that should give you a push in the right direction.

-Brent