// a persistent list that only grows (or is clear()ed)
// Note: don't put in static initializer (programID not set yet)
static class PersistentLog<A> extends AbstractList<A> {
  new L<A> l;
  File file;
  
  PersistentLog(S fileName) {
    this(getProgramFile(fileName));
  }
  
  PersistentLog(S progID, S fileName) {
    this(getProgramFile(progID, fileName));
  }
  
  *(File *file) {
    for (S s : scanLog(file)) pcall {
      l.add((A) unstructure(s));
    }
  }
  
  public synchronized int size() {
    ret l.size();
  }
  
  public synchronized A get(int i) {
    ret l.get(i);
  }
  
  public synchronized bool add(A a) {
    l.add(a);
    logQuoted(file, structure(a));
    ret true;
  }
  
  S fileContents() {
    ret loadTextFile(file);
  }
  
  public synchronized void clear() {
    l.clear();
    file.delete();
  }
}