void myFunc(unsigned int i = 0) { Serial.println(i); }
void test(int del = 1000) {
  for (byte x=0; x<2; x++)
    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN)), 
    delay(del);
}

void callFn(void(*f)()){ (*f)(); }
void callFn_args(void(*fn)(void *), void *p){ fn(p); }

void printMe(char txt[]) {
  Serial.println(txt);
}


void lambda() {
  byte num = 666;
  callFn([]() -> void { myFunc(); });
}

void setup() {
	Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);
  const char* msg = "OK";

  callFn([]() -> void { myFunc(66); });
  callFn_args(myFunc, 99);
  callFn_args(printMe, "hello");
  callFn_args(printMe, msg);
}


void loop() { }