anchor.diff:  -behaviour(gen_server).
   
   %% API functions
  --export([start_link/0]).
  +-export([start_link/0,
  +         stop/0,
  +         evaluate/1]).
   
   %% gen_server callbacks
   -export([init/1,
  
positive.code:     lager:info("Evaluating: ~p", [String]),
      gen_server:call(?MODULE, {eval, String}).
  
  %%%===================================================================
  %%% gen_server callbacks
  %%%===================================================================
  
negative.code:          handle_info/2,
           terminate/2,
           code_change/3]).
  
  -record(state, {context}).
  
  