kubek2k

pivot(_, [], [], []).
pivot(Pivot, [Head|Tail], [Head|LessOrEqualThan], GreaterThan) :- Pivot >= Head, pivot(Pivot, Tail, LessOrEqualThan, GreaterThan). 
pivot(Pivot, [Head|Tail], LessOrEqualThan, [Head|GreaterThan]) :- pivot(Pivot, Tail, LessOrEqualThan, GreaterThan).

quicksort([], []).
quicksort([Head|Tail], Sorted) :- pivot(Head, Tail, List1, List2), quicksort(List1, SortedList1), quicksort(List2, SortedList2), append(SortedList1, [Head|SortedList2], Sorted).