// 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));
  }
}