anchor.diff:  
   %-define(TRACE(X,Y), io:format(X,Y)).
   -define(TRACE(X,Y), ok).
  +
  +-define(LOG_CC_FAILS, false).
  +%%-define(LOG_CC_FAILS, true).
  +
   -include("scalaris.hrl").
   -include("client_types.hrl").
   
  
positive.code:           { false =:= WL
              orelse TxId =:= WL, {txid_mismatch, WL, TxId} },
            { [] =:= RL,          {readlock_not_empty, RL} } ],
      cc_return_val(cc_set_wl, Checks, _UI_if_ok = none, _Log = true).
  
  -spec wf_set_wl
         (prbr_bottom, UI :: none, {txid_on_cseq:txid(), -1}) -> db_entry();
  
negative.code: cc_single_write({RL, WL, Vers}, _WriteFilter, _Val) ->
      Checks = [ { [] =:= RL,    readlock_is_set },
                 { false =:= WL, writelock_is_set } ],
      cc_return_val(cc_single_write, Checks, _UI_if_ok = Vers, ?LOG_CC_FAILS).
  
  -spec wf_set_vers_val(db_entry() | prbr_bottom, version(),
                        client_value()) -> db_entry().
  