void setup() {
  // put your setup code here, to run once:
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
}

/* Digit table for the 7-segment display */
const uint8_t digitTable[] = {
  0b11000000,
  0b11111001,
  0b10100100,
  0b10110000,
  0b10011001,
  0b10010010,
  0b10000010,
  0b11111000,
  0b10000000,
  0b10010000,
  0b11111111,
};

bool isPrime(int num) {
  if (num < 2) return false;

  for (int j = 2; j < num/2 + 1; j++) {
    if (num%j == 0) {
      return false;
    }
  }

  return true;
}

int i = 0;
void loop() {
  // put your main code here, to run repeatedly:
  // for (int i = 0; i < 10; i++) {
  //   displayNumber(i);
  //   delay(1000);
  // }

  if (isPrime(i)) {
    displayNumber(i);
    delay(1000);
  }
  
  i++;

  if (i > 9) {
    i = 0;
  }
}

void displayNumber(int num) {
  // Ensure the number is within the valid range (0-9)
    uint8_t segments = digitTable[num];

    // Display the number on the 7-segment display
    digitalWrite(2, bitRead(segments, 0));
    digitalWrite(3, bitRead(segments, 1));
    digitalWrite(4, bitRead(segments, 2));
    digitalWrite(5, bitRead(segments, 3));
    digitalWrite(6, bitRead(segments, 4));
    digitalWrite(7, bitRead(segments, 5));
    digitalWrite(8, bitRead(segments, 6));
}