sclass Best_comparable<A> {

  A best;

  Comparable score;

  bool verboseNewBest, replaceIfSameScore;

  transient O onChange;

  transient O stringifier; // func(A) -> S

  synchronized bool isNewBest(Comparable score) {

    ret this.score == null

      || (replaceIfSameScore

        ? cmp(score, this.score) >= 0

        : cmp(score, this.score) > 0);

  }

  synchronized Comparable bestScore() {

    ret score;

  }

  Comparable score() { ret bestScore(); }

  Comparable getScore() { ret bestScore(); }

  synchronized float floatScoreOr(float defaultValue) {

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

  }

  bool put(Pair<? extends A, Comparable> p) {

    ret p != null && put(p.a, p.b);

  }

  bool put(Best<? extends A> b) {

    ret b != null && put(b!, b.score);

  }

  bool put(A a, Comparable score) {

    ping();

    bool change;

    if (a != null) synchronized(this) {

      if (isNewBest(score)) {

        best = a;

        this.score = score;

        set change;

      }

    }

    if (change) {

      if (verboseNewBest) print("New best! " + this);

      pcallF(onChange);

    }

    ret change;

  }

  synchronized A get() { ret best; }

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

  synchronized Pair<A, Comparable> pair() { ret main pair(best, bestScore()); }

  synchronized A getIfScoreAbove(Comparable x) { ret cmp(x, score()) >= 0 ? best : null; }

  toString {

    ret !has() ? "-" : "Score " + score + ": " + callStringifier(stringifier, best);

  }

  bool putAndPrintIfNewBest(A a, Comparable score) {

    if (!put(a, score)) false;

    ret true with print(this);

  }

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

}