prolog-AI

% ex. 2
rotaction(L,_,0,L).
rotaction(L,Dir,N,Res):- -N > 0, N1 is N-1, rot(L,Dir,L1), rotaction(L1,Dir,n1,Res).
rot(L,st,L1):- rotst(L,L1).
rot(L,dr,L1):- rotdr(L,L1).
rotst([],[]).
rotst([X|R],L):- append(R,[X],L).
rotdr([],[]).
rotdr(L,[X|L1]):- ultim(L,L1,X).
ultim([X],[],X).
ultim([Y|R],[Y|L1],X):- ultim(R,L1,X).

% ex. 3
list_sub([],[]).
list_sub([_|Xs],Ys) :-list_sub(Xs,Ys).
list_sub([X|Xs],[X|Ys]) :-list_sub(Xs,Ys).

sublist_of(Sub,List) :-list_sub(List,Sub).

list_sublist_sum(Xs,S,Target) :- sublist_of(S,Xs),
sum(S,#=,Target).