anchor.diff:      check_and_set_param/2,
       show_params/0,
       check_params/0,
  -    log_param_errors/1
  +    log_param_errors/1,
  +    is_node_mod/1
     ]).
   
   %% application(3erl) callbacks.
  
positive.code:     false;
  is_param_valid(node_mods, Mods) ->
      Fun = fun(Mod) ->
          try
              Mod:module_info(),
              true = erlang:function_exported(Mod, tags, 0),
              true = erlang:function_exported(Mod, construct_token, 3),
              true = erlang:function_exported(Mod, node_pres, 1),
              false
          catch
              _:_ ->
                  true
          end
      end,
      case lists:filter(Fun, Mods) of
          [] -> true;
  
negative.code:       "~s: unknown parameter \"~s\".~n",
        [?APPLICATION, Param]),
      log_param_errors(Rest).
  
  is_node_mod(Mod) ->
      try
          Mod:module_info(),
          true = erlang:function_exported(Mod, tags, 0),
          true = erlang:function_exported(Mod, construct_token, 3),
          true = erlang:function_exported(Mod, node_pres, 1),
          true
      catch
          _:_ ->
              false
      end.
  
  %% -------------------------------------------------------------------
  %% application(3erl) callbacks.
  