Go Program to Print All Prime Numbers Within a Range

1. Introduction

A prime number is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. In other words, if a number is prime, it has only two distinct positive divisors: 1 and itself. For example, 5 is prime because the only ways to create the number 5 by multiplying integers are 1 × 5 or 5 × 1. In contrast, numbers greater than 1 that have more than two positive divisors are called composite. Notably, 1 is neither prime nor composite.

In this tutorial, we'll construct a Go program to list all prime numbers within a designated range.

2. Program Overview

Our Go program is constructed to:

1. Request the user to stipulate a range (start and end points).

2. Determine all prime numbers within the given range.

3. Exhibit the identified prime numbers to the user.

3. Code Program

// We initiate our Go program by declaring the main package.
package main

// The fmt package is incorporated to oversee input and output proceedings.
import "fmt"

// Function to check if a number is prime.
func isPrime(num int) bool {
    if num <= 1 {
        return false
    }
    for i := 2; i*i <= num; i++ {
        if num % i == 0 {
            return false
        }
    }
    return true
}

// Function to display all prime numbers within a specified range.
func primesInRange(start, end int) []int {
    var primes []int
    for i := start; i <= end; i++ {
        if isPrime(i) {
            primes = append(primes, i)
        }
    }
    return primes
}

// Our program's execution originates from the main function.
func main() {
    var start, end int

    // Users are prompted to provide the range's start and end points.
    fmt.Print("Enter the start of the range: ")
    fmt.Scan(&start)
    fmt.Print("Enter the end of the range: ")
    fmt.Scan(&end)

    // Display the prime numbers located within the provided range.
    fmt.Printf("Prime numbers between %d and %d are: %v\n", start, end, primesInRange(start, end))
}

Output:

Assuming the user defines the range as 10 to 50, the program's output would be:
Prime numbers between 10 and 50 are: [11 13 17 19 23 29 31 37 41 43 47]

4. Step By Step Explanation

1. Package and Import Statements: The expedition begins with the package main assertion, indicating our program's commencement. The fmt package is utilized for I/O operations.

2. Prime Check Function: The isPrime function ascertains if a provided integer is prime. A number less than or equal to 1 is immediately dismissed. The function then verifies if the number has divisors other than 1 and itself.

3. Function to Identify Primes in Range: The primesInRange function traverses each number within the designated range and appends prime numbers to the primes slice.

4. Variable Initialization: Two integer variables, start and end, are initialized to store the range's boundaries.

5. User Input and Display: After gathering the range limits, the program calculates and presents the prime numbers within the said range.

Continue Learning with Java Guides

Want to take your programming skills to the next level? Explore my practical Udemy courses on Java, Spring Boot, Microservices, Full-Stack Development, Docker, and Generative AI. You can also follow my structured learning roadmaps to become a professional developer.

Explore My Udemy Courses View Developer Roadmaps

By Ramesh Fadatare - Udemy Instructor Partner