anchor.diff:  make_vars(Vs) -> [ #k_var{name=V} || V <- Vs ].
   
   add_var_def(V, St) ->
  -    St#kern{ds=sets:add_element(V#k_var.name, St#kern.ds)}.
  +    St#kern{ds=cerl_sets:add_element(V#k_var.name, St#kern.ds)}.
   
   %%add_vars_def(Vs, St) ->
   %%    Ds = foldl(fun (#k_var{name=V}, Ds) -> add_element(V, Ds) end,
  
positive.code: 	       ff,				%Current function
  	       vcount=0,			%Variable counter
  	       fcount=0,			%Fun counter
  	       ds=[],				%Defined variables
  	       funs=[],				%Fun functions
  	       free=[],				%Free variables
  	       ws=[]   :: [warning()],		%Warnings.
  
negative.code: %%  handling.
  
  pattern(#c_var{anno=A,name=V}, _Isub, Osub, St0) ->
      case cerl_sets:is_element(V, St0#kern.ds) of
  	true ->
  	    {New,St1} = new_var_name(St0),
  	    {#k_var{anno=A,name=New},
  	     set_vsub(V, New, Osub),
  	     St1#kern{ds=cerl_sets:add_element(New, St1#kern.ds)}};
  	false ->
  	    {#k_var{anno=A,name=V},Osub,
  	     St0#kern{ds=cerl_sets:add_element(V, St0#kern.ds)}}
      end;
  pattern(#c_literal{anno=A,val=Val}, _Isub, Osub, St) ->
      {#k_literal{anno=A,val=Val},Osub,St};
  