Prolog:Testing 2 lists for similarity

Question

How can the elements of two different lists be checked for equality? Without, the first and the last entry. Unfortunately my approach does not work and unfortunately I cannot find my mistake.

isNearlyEqual(L1,L2) :-
    drop(L1,0,LA1),size(L1,X),drop(L1,X,LA1),
    drop(L2,0,LA2),size(L2,Y),drop(L2,Y,LA2),
    size(LA1,size1).
% My idea is now to check the 2 fragments of the list for equality. But I don't know how at the moment.
% First he removes the first and the last element.
% Then he should check the list for equality.
    
drop(Xs,N,Rs) :-
  integer(N),
  N > 0,
  drop(Xs,1,N,Rs).

drop( []     , _ , _ , [] ) .
drop( [X|Xs] , P , N , Rs ) :-
  ( 0 =:= P mod N -> R1 = Rs ; [X|R1] = Rs ) ,
  P1 is P+1 ,
  drop(Xs,P1,N,R1).
  
  
size([],0).

size([_|T],N):-
    size(T,M),
    N is M+1.

size_sub([],[]).

size_sub([H|T],[N|T2]):-
    size(H,N),
    size_sub(T,T2).

Answer 1

You defined the condition

    N > 0

in your drop/3 predicate, but also you are trying to do

    drop(L1,0,LA1)

so the predicate is always false

As I understand your problem, try this solution

    isNearlyEqual([_|T],[_|T2]) :-
        removeLast(T,L1),
        removeLast(T2,L2),
        completeEqual(L1, L2).

    completeEqual([],[]).
    completeEqual([H|T], [H2|T2]):-
        completeEqual(T,T2),
        H == H2.

    removeLast([_],[]).
    removeLast([H|[H2|T2]], Z):-
        removeLast([H2|T2],Z1),
        append([H],Z1,Z).