static <A, B> F1<F1<A, B>, Double> f1_scorePreciseRecognizer(final LPair<A, B> trainingList) {
  ret func(F1<A, B> recognizer) -> Double {
    new Scorer scorer;
    for (Pair<A, B> p : trainingList)
      scorer.add(recognizer.get(p.a) == p.b);
    ret scorer!;
  };
}