sclass Lowest<A> is IBest<A> {

  A best;

  double score;

  transient O onChange;

  synchronized bool isNewBest(double score) {

    ret best == null || score < this.score;

  }

  synchronized double bestScore() {

    ret best == null ? Double.NaN : score;

  }

  double score() { ret bestScore(); }

  synchronized float floatScore() {

    ret best == null ? Float.NaN : (float) score;

  }

  synchronized float floatScoreOr(float defaultValue) {

    ret best == null ? defaultValue : (float) score;

  }

  public bool put(A a, double score) {

    bool change = false;

    synchronized(this) {

      if (a != null && isNewBest(score)) {

        best = a;

        this.score = score;

        change = true;

      }

    }

    if (change)

      pcallF(onChange);

    ret change;

  }

  synchronized void clear() { best = null; score = 0; }

  synchronized A get() { ret best; }

  synchronized bool has() { ret best != null; }

  synchronized Pair<A, Double> pair() { ret best == null ? null : Pair(best, bestScore()); }

  toString {

    ret "Score " + formatDouble_significant2(score, 4) + ": " + best;

  }

}