[Haskell-beginners] Questions About Rose Trees Analysis

[Lorenzo Isella]

Dear All,
I am trying to learn Haskell (for the second time), but I have to
admit I am still struggling with relative simple stuff, so I ask if
anybody can give me a hand.
I am dealing with the issues of extracting info out of some rose trees
and probably I am also having some troubles with the notation.

The rose tree is defined with the following notation

data Rose a = a :> [Rose a]
deriving (Eq, Show)

and the root can be detected simply as

root (a :> rs) = a

I would like to have the expression (with the ":>" notation for the
Node) of the function to find the children of the root. Example of
expected behavior of this function children

children (1 :> [2 :> [], 3 :> []]) = [2 :> [], 3 :> []]

On top of that, I am trying to get the functions to have the functions

 size :: Rose a -> Int
 leaves :: Rose a -> Int

that count the number of nodes in a rose tree, respectively the number
of leaves (nodes without any children).
For the children function, I have tried stuff like

children (a :> rs) = rs

quite unsuccessfully.

Any suggestion is appreciated.
Cheers

Lorenzo