anchor.diff:  -spec rep_receive(fun((fun()) -> term())) -> term().
   
   rep_receive(Fun) ->
  -    %% See instrumentation for more details.
  -    Result = rep_receive_aux(Fun),
  -    rep_yield(),
  -    Result.
  +    rep_receive_aux(Fun).
   
   rep_receive_aux(Fun) ->
       Fun(fun() -> block(), rep_receive_aux(Fun) end).
  
positive.code: -spec rep_send(dest(), term()) -> term().
  
  rep_send(Dest, Msg) ->
      %% See instrumentation for more details.
      {_Self, RealMsg} = Dest ! Msg,
      sched ! #sched{msg = send, pid = self(), misc = [Dest, RealMsg]},
      rep_yield(),
      Msg.
  
  %% Replacement for spawn/1.
  %% The argument provided is the argument of the original spawn call.
  
negative.code: 
  rep_receive_notify(From, Msg) ->
      sched ! #sched{msg = 'receive', pid = self(), misc = [From, Msg]},
      rep_yield(),
      ok.
  
  %% Replacement for send/2 (and the equivalent ! operator).
  