anchor.diff:  
   
   %% API
  +-export([cancel/2]).
   -export([yield/4]).
   -export([error/5]).
   
  
positive.code: 
                  invocation_id = none,
                  callee_pids = [],
                  results = []
                  }).
  
  start(Args) ->
  
negative.code:   %% gen_server.
  
  
  cancel(Pid,Options) ->
    gen_server:call(Pid,{cancel,Options}).
  
  yield(Pid,Options,Arguments,ArgumentsKw) ->
    gen_server:cast(Pid,{yield,Options,Arguments,ArgumentsKw,self()}).
  
  error(Pid,Details,ErrorUri,Arguments,ArgumentsKw) ->
    gen_server:cast(Pid,{error,Details,ErrorUri,Arguments,ArgumentsKw,self()}).
  
  init(Args) ->
    case check_and_create_state(Args) of
  