% The split(A,Small,Large,List) relation describes the work of the % quicksort partitioning (split) algorithm. It means that elements % of List contain exactly all the elements of Small and Large, and the item A, % and all the members of small are < A, and all the members of large are % >= A. split(_,[],[],[]). split(A,[S|Smalltail],Large,[S|Tail]) :- S < A, split(A,Smalltail,Large,Tail). split(A,Small,[S|Largetail],[S|Tail]) :- S >= A, split(A,Small,Largetail,Tail). % Perform sorting by quicksort. sorted([], []). sorted([Pivot|Tail], S) :- split(Pivot, Small, Large, Tail), sorted(Small,SSmall), sorted(Large,SLarge), append(SSmall, [Pivot|SLarge], S).