static class LFunctionPlusPrevious extends LearnerImpl {

  static boolean debug;

  Stepper stepper;

  new List<O[]> examples;

  public void processInOut(O in, O out) {

    examples.add(new O[] {in, out});

    if (stepper == null)

      stepper = new Stepper(allFunctions(), solvedCases());

    while (!stepper.ended()) {

      if (check(stepper.current()))

        ret; // ok, keep

      else

        stepper.step();

    }

    fail();

  }

  boolean check(O[] fg) {

    if (debug) debug("Checking " + structure(fg));

    for (O[] e : examples) {

      O o = tryProcess((Function) fg[0], e[0]);

      if (o != null) {

        O x = tryProcess(((Case) fg[1]).winner, o);

        if (e[1].equals(x))

          continue; // example ok

      }

      ret false;

    }

    ret true; // all examples ok

  }

  public O processIn(O in) {

    Object[] fg = stepper.current();

    ret ((Case) fg[1]).processIn(((Function) fg[0]).process(in));

  }

  static class Stepper {

    List<Function> functions;

    List<Case> cases;

    int i1, i2;

    *(List<Function> *functions, List<Case> *cases) {}

    boolean ended() {

      ret i1 >= functions.size();

    }

    O[] current() {

      ret new O[] {functions.get(i1), cases.get(i2)};

    }

    void step() {

      if (i2 < cases.size()-1) ++i2;

      else { ++i1; i2 = 0; }

    }

  }

}