domains
    ilist=integer*
 predicates
    mp_sort(ilist,ilist)
    order(integer,integer)
    append(ilist,ilist,ilist)
 clauses
    mp_sort([X],[X]):-!.
    mp_sort(L,S):-
      append(X,[A,B|Y],L),
      order(B,A),
      append(X,[B,A|Y],M),
      !,
      mp_sort(M,S).
    mp_sort(L,L).
    
    append([],L,L).
    append([H|T],L1,[H|L2]):-append(T,L1,L2).
    order(X,Y):-X<=Y.