// a persistent list using a clever combination of persisting and logging
// (well, only logging as of now)
// Note: don't put in static initializer (programID not set yet)

static class PersistentList<A> extends AbstractList<A> {
  new List<A> m;
  File file;
  
  PersistentList(S fileName) {
    this(getProgramFile(fileName));
  }
  
  PersistentList(S progID, S fileName) {
    this(getProgramFile(progID, fileName));
  }
  
  *(File *file) {
    for (S s : scanLog(file)) pcall {
      L l = cast unstructure(s);
      if (eq(l.get(0), "add"))
        m.put((A) l.get(1), (B) l.get(2));
      else if (eq(l.get(0), "remove"))
        m.remove((A) l.get(1));
      else
        print("Unknown command in log: " + l.get(0));
    }
  }
  
  // just delegates
  
  public int size() {
    ret m.size();
  }
  
  public B get(int i) {
    ret m.get(i);
  }
  
  // TODO: calling remove() in the iterator will have unpersisted
  // effects.
  public Set<Map.Entry<A,B>> entrySet() {
    ret m.entrySet();
  }
  
  // delegates with logging

  public B put(A a, B b) {
    B result = m.put(a, b);
    logQuoted(file, structure(litlist("add", a, b)));
    ret result;
  }
  
  public B remove(O a) {
    B result = m.remove(a);
    logQuoted(file, structure(litlist("remove", a)));
    ret result;
  }
}

Began life as a copy of #1002063