// goes well with the stage {} macro (see tok_stages)
srecord Stages(new L</*Stage*/Runnable> stages) is Steppable, Runnable {
  replace Stage with Runnable.
  int iStage;
  Stage stage;
  
  public bool step() {
    // What is this funny syntax
    ret iStage <= l(stages)
      && trueBecause(callF(stage = _get(stages, iStage++)));
  }
  
  Stage stage(Stage stage) {
    stages.add(stage);
    ret stage;
  }
  
  Stage stage(S name, Stage stage) {
    ret stage(runnableWithCustomToString(name, stage));
  }
  
  run { stepAll(this); }
  
  int indexOfStage(Stage stage) {
    ret stages.indexOf(stage);
  }
  
  void stepUntilStage(Stage stage) {
    int index = indexOfStage(stage);
    while (iStage <= index && step()) {}
  }
}