sclass Prog_If_Multi implements Runnable {
  LPair<F0<Bool>, Runnable> conditions = new L;
  Runnable defaultBranch;
  
  public void run {
    for (Pair<F0<Bool>, Runnable> p : conditions)
      if (callF(p.a))
        ret with callF(p.b);
    callF(defaultBranch);
  }
  
  void add(F0<Bool> condition, Runnable branch) {
    addPair(conditions, condition, branch);
  }
}

Began life as a copy of #1020555