Remember the `init` function of Haskell? It can be defined in Haskell

as:

init :: [a] -> [a]

init [_] = []

init (x:xs) = x : init xs

Formulate the appropriate Prolog rule `init(Xs,Ys)` which is true if

(and only if) `Ys` is the initial part of `Xs`. That is, the query

`init([1,2,3,4,5],[1,2,3,4]).` would evaluate to `true`, or the query

`init([1,2,3,4,5],Ys).` would give `Ys = [1,2,3,4]`

Hint: this rule will be recursive, and will have a corresponding base

case and recursive case, each analogous to the base case and recursive

case, respectively, of the above Haskell function --- the main

difference being that the Prolog rule `init(Xs,Ys)` is a predicate,

not a function