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: 
  function({#c_var{name={F,Arity}=FA},Body}, St0) ->
      try
  	St1 = St0#kern{func=FA,ff=undefined,vcount=0,fcount=0,ds=cerl_sets:new()},
  	{#ifun{anno=Ab,vars=Kvs,body=B0},[],St2} = expr(Body, new_sub(), St1),
  	{B1,_,St3} = ubody(B0, return, St2),
  	%%B1 = B0, St3 = St2,				%Null second pass
  