Prime Number Program In Dart

In this tutorial, we will learn how to write a program in Dart that identifies prime numbers. Prime numbers are critical in various fields, including cryptography, computer science, and mathematics. Understanding prime numbers can help programmers optimize algorithms and solve complex problems efficiently.

What is a Prime Number?

A prime number is a natural number greater than 1 that has no divisors other than 1 and itself. For example, the numbers 2, 3, 5, 7, and 11 are prime numbers. They are significant because they can only be divided evenly by 1 and themselves, making them the building blocks of whole numbers. Primes are used in algorithms for encryption, hashing, and generating random numbers.

Syntax

// Function to check if a number is prime
bool isPrime(int number) {
  // Check if number is less than 2 (not prime)
  if (number < 2) return false;
  
  // Loop from 2 to the square root of the number
  for (int i = 2; i * i <= number; i++) {
    // If number is divisible by i, it's not prime
    if (number % i == 0) return false;
  }
  
  // If no divisors found, it's prime
  return true;
}

How It Works

1. Check for Validity: The function first checks if the number is less than 2. If it is, the function returns false since numbers less than 2 are not prime.
2. Loop Through Possible Divisors: It then loops from 2 to the square root of the number. This is efficient because if a number is divisible by any number greater than its square root, it must also be divisible by a number smaller than its square root.
3. Check for Divisibility: Inside the loop, it checks if the number is divisible by i. If it finds any divisor, it returns false.
4. Return True: If no divisors are found, the function returns true, indicating the number is prime.

Example 1: Basic Usage

Example
Copy
void main() {
  int number = 7; // Number to check for primality
  
  // Call the function to check if the number is prime
  if (isPrime(number)) {
    print('$number is a prime number.'); // Output if prime
  } else {
    print('$number is not a prime number.'); // Output if not prime
  }
}
Try it Yourself

Output:

7 is a prime number.

Explanation: The program checks if 7 is prime and prints the result.

Example 2: Check Multiple Numbers

void main() {
  List<int> numbers = [10, 13, 17, 20]; // List of numbers to check
  
  // Loop through each number in the list
  for (int number in numbers) {
    // Check if the number is prime and print the result
    if (isPrime(number)) {
      print('$number is a prime number.');
    } else {
      print('$number is not a prime number.');
    }
  }
}

Output:

10 is not a prime number.
13 is a prime number.
17 is a prime number.
20 is not a prime number.

Explanation: This example checks a list of numbers and prints whether each is prime.

Example 3: Real-World Application

void main() {
  // Generate a list of prime numbers up to a certain limit
  int limit = 50; // Limit for generating prime numbers
  List<int> primes = []; // List to hold prime numbers
  
  // Loop through numbers from 2 to limit
  for (int number = 2; number <= limit; number++) {
    // Check if the number is prime
    if (isPrime(number)) {
      primes.add(number); // Add prime to the list
    }
  }
  
  // Print all prime numbers found
  print('Prime numbers up to $limit: $primes');
}

Output:

Prime numbers up to 50: [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47]

Explanation: This example generates and prints all prime numbers up to 50.

When to Use Prime Number Program in Dart

Key Points

This tutorial should give you a solid foundation to understand and implement prime number checks in Dart. Happy coding!