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 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, 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.