anchor.diff:      F = {function,0,Name,A,[{clause,0,Args,[],Body}]},
       NA = {Name,A},
       {[F|Fs],St#expand{exports=add_element(NA, St#expand.exports),
  -		      defined=add_element(NA, St#expand.defined)}}.
  +		      defined=gb_sets:add_element(NA, St#expand.defined)}}.
   
   %% define_function(Form, State) -> State.
   %%  Add function to defined if form is a function.
  
positive.code:     end.
  
  defined(F, A, St) ->
      ordsets:is_element({F,A}, St#expand.defined).
  
negative.code:     PreDef=[{behaviour_info,1}],
      PreExp=PreDef,
      {[gen_beh_info(Callbacks)],
       St#expand{defined=gb_sets:union(gb_sets:from_list(PreDef), Defined),
  	       exports=union(from_list(PreExp), Exports)}}.
  
  gen_beh_info(Callbacks) ->
  