anchor.diff:      end;
   function_arity(_) -> no.
   
  -%% pass_eval_set(Args, Env, State) -> {Env,State}.
  +%% pass_eval_set(Args, Env, State) -> {Set,Env,State}.
   %%  Evaluate the set form.
   
   pass_eval_set(Args, Env, St) ->
  
positive.code:     KVs = foldr(fun ({K,V}, Acc) -> [K,V|Acc] end, [], Ps),
      exp_backquote(KVs, N).
  -else.
  exp_bq_map_pairs(_, _) -> map.
  -endif.
  
  new_symb(St) ->
  
negative.code: 
  op_pairs([[V,_]|Ls], Op) ->
      element(1, mapfoldl(fun ([V,_], Acc) -> {exp_bif(Op, [Acc,V]),V} end,
                          V, Ls)).
  
  %% exp_nequal(Args, Op, State) -> {Exp,State}.
  %%  Expand not equal test strictly forcing evaluation of all
  