anchor.diff:  
   %% API
   -export([start_link/0,
  +         get_posts/1,
            login/0,
            post/2,
            is_logged_in/0
  
positive.code:         [],
          []
       ).
  
negative.code: 
  is_logged_in() ->
      gen_server:call(?MODULE, {is_logged_in}).
  
  get_posts(Feed) ->
      gen_server:call(?MODULE, {get_posts, Feed}).
  
  %%%===================================================================
  %%% gen_server callbacks
  