Question on speed of set operations

[reinert <reinkor@gmail.com>]

Dear all,

I try to make an "Include" procedure similar to

procedure Include(Container: in out Set; New_Item: in Element_Type);

(under Containers.Ordered_sets) and where one includes 
(eventually replaces) elements in a set instead of including 
one element at a time. The intention is to make the user code 
clean/readable and efficient.

So what is the best alternative among the following tree procedures
for the above purpose (in terms of *speed*):

procedure Include(Container: in out Set; New_Items: in Set) is
begin
   for e of New_Items loop
       Container.Include(e);
   end loop;
end include_set;

procedure Include(Container: in out Set; New_Items: in Set) is
begin
   Container.Difference(New_Items);
   Container.Union(New_Items);
end include_set;

procedure Include(Container: in out Set; New_Items: in Set) is
begin
   Container := New_Items or Container
end include_set; 

Could there be other/better alternatives? And/or am I trying
to reinvent the wheel?

reinert