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1

Hello Everyone,
My name is Brandon and I am new to the Arduino environment. I was experimenting with the serial monitor by taking a function I had from an old Data Structs assignment and converting it to the Arduino IDE. Please take a look at my code and respond with any comments or suggestions as to how I can improve the code to be more suited for the cause. Thank you

//Brandon Markham
//Prime Integer Algorithm
//05/16/20

int userNum;
int origNum;
int count;
char userChoice;


void setup() {
  Serial.begin(9600);
  Serial.println("Please enter an integer greater than 2 to see if it is prime.");
  Serial.println("If the entered number is not prime, the program will display ");
  Serial.println("the closest prime integer less than the number entered.\n");
}

void loop() {
  while (Serial.available() == 0) {
  }

  userNum = Serial.parseInt();
  Serial.print("Number entered was: ");
  Serial.println(userNum);

  while (userNum <= 2) {
    Serial.println("Please enter a valid input greater than 2.\n");

    while (Serial.available() == 0) {
    }
    userNum = Serial.parseInt();
    Serial.print("The number entered was: ");
    Serial.println(userNum);
  }

  origNum = userNum;
  PrimeInteger(userNum, origNum, count);

  Serial.print("Would you like to test another integer?\n");
  Serial.print("Select Y for yes and N for no.\n\n");

  while (Serial.available() == 0) {
  }
  userChoice = Serial.read();
  Serial.print("User choice was: ");
  Serial.println(userChoice);

  while (userChoice != 'y' && userChoice != 'Y' && userChoice != 'n' && userChoice != 'N') {
    Serial.println("Please enter valid input Y/y or N/n.\n");

    while (Serial.available() == 0) {
    }
    userChoice = Serial.read();
    Serial.print("User choice was: ");
    Serial.println(userChoice);
  }

  while (userChoice == 'Y' || userChoice == 'y') {
    Serial.println("Please enter another integer greater than 2.\n");
    break;
  }

  while (userChoice == 'N' || userChoice == 'n') {
    Serial.println("This program has terminated successuflly.");
    delay(1000);
    exit(0);
  }
}

void PrimeInteger(int uNum, int oNum, int c) {

  bool isPrimeInteger = true;

  if (uNum <= 1) {
    isPrimeInteger = false;
  }

  for (int i = 2; i <= uNum / 2; ++i) {
    if (uNum % i == 0) {
      isPrimeInteger = false;
      break;
    }
  }

  if (isPrimeInteger && c > 0) {
    Serial.print(uNum);
    Serial.print(" is the closest prime integer to ");
    Serial.print(oNum);
    Serial.println(".");
    Serial.println();
    return;
  }

  else if (isPrimeInteger) {
    Serial.print(uNum);
    Serial.print(" is a prime number\n");
    Serial.println();
    return;
  }

  if (!isPrimeInteger) {
    c++;
    uNum = uNum - 1;
    PrimeInteger(uNum, oNum, c);
  }
}
3

There is a special loop for these occasions where you need to do a calculation before you can write the 'while' test: do {} while (condition); The body of the loop is always done once so you don't have to write the same code above the loop as in the loop:

  do {
    while (Serial.available() == 0) {}
    userNum = Serial.parseInt();
    Serial.print("Number entered was: ");
    Serial.println(userNum);
    if (userNum <= 2) {
      Serial.println("Please enter a valid input greater than 2.\n");
  } while (userNum <=2);
4

why not

void loop() {
    if (Serial.available()) {
        userNum = Serial.parseInt();
        if (userNum < 2)
            Serial.println ("  invalid number <2");
        else  {
            Serial.print ("  ");
            Serial.print (userNum);
            Serial.print ("  ");
            PrimeInteger(userNum, origNum, count);
        }
        Serial.println("enter a number");
    }
}

is there any point in terminating the program?

5

The call

Returns a long and not an int.

Depending on the platform you use, an int might be quite limiting (2 bytes on uno for example). I would suggest to use long for the user input and the maths.

6

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