File : qsort.adb

procedure QSort(Items: in out ItemVec; L,R: in Integer) is
  I: Integer := L;
  J: Integer := R;
  X: constant Item := Items((L+R)/2);
  Y: Item;
begin
  loop
    while Items(I)>X loop I:=I+1; end loop;
    while X>Items(J) loop J:=J-1; end loop;
    if I <= J then
      Y:=Items(I); Items(I):=Items(J); Items(J):=Y;
      I:=I+1; J:=J-1;
    end if;
    exit when I>J;
  end loop;
  if L<J then QSort(Items,L,J); end if;
  if I<R then QSort(Items,I,R); end if;

end QSort;