code: function CallbackArray(){
      this.callbacks = new SortedArray(
          function(a,b){
              if (a.uid < b.uid) {return -1;};
              if (a.uid > b.uid) {return  1;};
              if (a.counter < b.counter){ return -1;};
              if (a.counter > b.counter){ return  1;};
              return 0;
          });
  }
docs: /*!
  \brief array containing the callback functions corresponding to the call
  of an answer. I.e. answer takes message and callback as arguments. Since
  the callbacks can be different each time, we must remember which callback
  call when we have the answer