// function type is A (e.g. String)
sclass FunctionTimings<A> {
  Map<A, Average> data = syncMap();
  
  meta-for Runnable also as RunnableWithExceptions {
    void do aka time(A function, Runnable r) ctex {
      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
  S render() {
    ret lines(ciSorted(map(get(), (f, avg) ->
      functionToString(f) + ": " + n2(iround(nsToMicroseconds(avg!)))
        + " " + microSymbol() + "s (" + n2(iround(avg.n())) + ")")));
  }
  
  S functionToString(A f) {
    ret firstToUpper(str(f));
  }
}