function invokeRecImmediate(scheduler, pair) {
      var state = pair[0], action = pair[1], group = new CompositeDisposable();
      action(state, innerAction);
      return group;

      function innerAction(state2) {
        var isAdded = false, isDone = false;

        var d = scheduler.schedule(state2, scheduleWork);
        if (!isDone) {
          group.add(d);
          isAdded = true;
        }

        function scheduleWork(_, state3) {
          if (isAdded) {
            group.remove(d);
          } else {
            isDone = true;
          }
          action(state3, innerAction);
          return disposableEmpty;
        }
      }
    }
Normalizes the specified TimeSpan value to a positive value.
@param {Number} timeSpan The time span value to normalize.
@returns {Number} The specified TimeSpan value if it is zero or positive; otherwise, 0