// function type is A (e.g. String)

sclass FunctionTimings<A> {

  Map<A, Average> data = syncMap();

  void doCtex aka timeCtex(A function, RunnableWithExceptions r) ctex {

    if (r == null) ret;

    long time = nanoTime();

    try {

      r.run();

    } finally {

      time = nanoTime()-time;

      saveTiming(function, time);

    }

  }

  <B> B get(A function, IF0<B> f) {

    if (f == null) null;

    new Var<B> var;

    time(function, -> var.set(f!));

    ret var!;

  }

  void do aka time(A function, Runnable r) {

    if (r == null) ret;

    long time = nanoTime();

    try {

      r.run();

    } finally {

      time = nanoTime()-time;

      saveTiming(function, time);

    }

  }

  void saveTiming(A function, long time) {

    Average avg = syncMapGetOrCreate(data, function, -> new Average);

    avg.add(time);

  }

  Map<A, Average> get() { ret cloneMap(data); }

  void reset aka clear() { data.clear(); }

  // as multi-line string, sorted alphabetically

  public S render aka toString() {

    ret lines(renderedEntries());

  }

  LS renderedEntries() {

    ret ciSorted(map(get(), (f, avg) ->

      functionToString(f) + ": " + n2(iround(nsToMicroseconds(avg!)))

        + " " + microSymbol() + "s (" + n2(iround(avg.n())) + ")"));

  }

  S toStringSingleLine() {

    ret joinWithComma(renderedEntries());

  }

  S functionToString(A f) {

    ret firstToUpper(str(f));

  }

}