anchor.diff:  delete(PropList, KeyOrKeys) ->
       Fun = fun(Term) ->
           if
  -            is_tuple(Term), is_list(KeyOrKeys) -> 
  +            is_tuple(Term), is_list(KeyOrKeys) ->
                   not lists:member(element(1, Term), KeyOrKeys);
               is_tuple(Term) ->
                   element(1, Term) /= KeyOrKeys;
  -            is_list(KeyOrKeys) -> 
  +            is_list(KeyOrKeys) ->
                   not lists:member(Term, KeyOrKeys);
               Term /= KeyOrKeys ->
                   true;
  
positive.code: 
  %% @doc Converts anything into a `atom()'.
  %% WARNING: Can create new atoms
  -spec to_atom(string()|binary()|atom()|integer()) -> 
      atom().
  
  to_atom(A) when is_atom(A) -> A;
  
negative.code: 
  %% @doc Similar to `get_value(Key, List, Default)' but converting the result into
  %% a `integer()' or `error'.
  -spec get_integer(term(), list(), term()) ->
      integer() | error.
  
  get_integer(Key, List, Default) ->
  