Fifteen Minutes to Wapner (day2) [SLiSW]

%some exercises (not all are from the book, And I had not done the last one from the book)

%compress
compress([], []).

compress([X], [X]).

compress([X, X|Tail], Result) :-
    compress([X|Tail], Result).

compress([X, Y|Tail], [X|Result]) :-
    compress([Y|Tail], Result).

%size of list
sizeOfList([],0).

sizeOfList([Head|Tail], N) :-
    sizeOfList(Tail, N1), N is N1 + 1.

%element at position
elementAt(0, [Head|_], Head).

elementAt(Pos, [_|Tail], Res) :-
    Pos1 is Pos - 1,
    elementAt(Pos1, Tail, Res).

%last number of list
lastNumber([List], List). %[List] is a list with just one element

lastNumber([_|Tail], N) :- lastNumber(Tail, N). % should ignore Head at the begining

%flatten list (example below)
%my_flatten([a, [b, [c, d], e]], X).
%X = [a, b, c, d, e]
myFlatten(Element,[Element]) :- \+ is_list(Element).

myFlatten([], []).

myFlatten([Head|Tail], Result) :-
    myFlatten(Head, Result1), myFlatten(Tail, Result2), append(Result1, Result2, Result).

%reverse a list

reverseList(List, Reversed) :-
    reverseList(List, [], Reversed).

reverseList([], Reversed, Reversed).

reverseList([Head|Tail], TheOther, Reversed) :-
    reverseList(Tail, [Head|TheOther], Reversed).

%after 2 days, a new method to reverse a list
reverseList([Element], [Element]).

reverseList([Head|Tail], Result) :-
    reverseList(Tail, Result1), append(Result1, [Head], Result).

%smallest in list
smallest([TheSmall], TheSmall).

smallest([Head|Tail], Res) :-
    smallest(Tail, Res1), Head > Res1 -> Res is Res1; Res is Head. % or ... smallest(Tail, Res1), Res is min(Head, Res1).

%sum list
sumList([],0).
sumList([Head|Tail], N) :-
    sumList(Tail, N1), N is N1 + Head.