struct Rocker {
  const byte pin;
  void (*callback)(const byte activePin);
  byte state;
};

// forward declaration of the callbacks, some could be shared and use the pin to differentiate action
void r2(const byte);
void r3(const byte);
void r4(const byte);
void r5(const byte);

Rocker rockers[] = {{2, r2}, {3, r3}, {4, r4}, {5, r5}};

void r2(const byte pin) {Serial.println(pin);}
void r3(const byte pin) {Serial.println(pin);}
void r4(const byte pin) {Serial.println(pin);}
void r5(const byte pin) {Serial.println(pin);}

void check() {
  bool antiBounceNeeded = false;
  for (auto && r : rockers) {
    byte s = digitalRead(r.pin);
    if (s != r.state) {
      antiBounceNeeded = true;
      r.state = s;
      r.callback(r.pin);
    }
  }
  if (antiBounceNeeded) delay(15); // anti bounce of the poor
}

void setup() {
  for (auto && r : rockers) {
    pinMode(r.pin, INPUT_PULLUP);
    r.state = digitalRead(r.pin);;
  }

  Serial.begin(115200);
}

void loop() {
  check();
}