list.pl

% Given a list L we want to find wether an element X is a member of that list or not.

member(X, [X | _ ]).

member(X, [Y | Rest]):-
    member(X, Rest).

% Concatenate list L1 and L2 to form list L3

concat([], L, L).

concat([X|L1], L2, [X|L3]):-
    concat(L1, L2, L3).

member1(X, L):-
    concat(L1, [X|L2], L).

% adding an item X to the beginning of a list L

add(X, L, [X|L]).

%delete the first occurence of the element X of a list L
del(X, [X|L], L).
del(X, [Y|Rest], [Y|L1]):-
    del(X, Rest, L1).

del_all(X, [], []).
del_all(X, [X|L], L1):-
    del_all(X, L, L1).
del_all(X, [Y|L], L1):-
    del_all(X, L, L2),
    concat([Y], L2, L1).

%find out the last member of a list.
lastmember([X], X).
lastmember([_|L], X):-
    lastmember(L, X).

%find the reverse of a list
reverselist([], []).
reverselist([X], [X]).
reverselist([X | L], L1):-
    reverselist(L, L2),
    concat(L2, [X], L1).

%check palindrome of a list
palindrome(L):-
    reverselist(L, L).

%insert in X in all possible positions
insert_all_pos(X, [], [X]).
insert_all_pos(X, [Y|T], [X,Y|T1]):-
    insert_all_pos(X, T, T1).

%check palindrome using concatenate
palindrome1([]).
palindrome1([_]).
palindrome1([H|T]):-
    concat(L, [H], T),
    palindrome1(L).

%check whether a list is of odd length
even([]).
odd([_]).
even([H|T]):-
    odd(T).
odd([H|T]):-
    even(T).

%find out the length of a list
length([], 0).
length([X|Y], N):-
    length(Y, N1),
    N1 is N-1.

%find all prefixes and suffixes of a list
prefix([], L).
prefix([X|Y], [X|Y1]):-
    prefix(Y, Y1).

suffix(L, L).
suffix(L1, [_|L2]):-
    suffix(L1, L2).

%find all permutations of a list