prime number calculator golang code example

Example 1: checking for prime numbers using golang

package main

import (
    "fmt"
    "math"
)

func IsPrime(value int) bool {
    for i := 2; i <= int(math.Floor(float64(value)/2)); i++ {
        if value%i == 0 {
            return false
        }
    }
    return value > 1
}

func IsPrimeSqrt(value int) bool {
    for i := 2; i <= int(math.Floor(math.Sqrt(float64(value)))); i++ {
        if value%i == 0 {
            return false
        }
    }
    return value > 1
}

func SieveOfEratosthenes(value int) {
    f := make([]bool, value)
    for i := 2; i <= int(math.Sqrt(float64(value))); i++ {
        if f[i] == false {
            for j := i * i; j < value; j += i {
                f[j] = true
            }
        }
    }
    for i := 2; i < value; i++ {
        if f[i] == false {
            fmt.Printf("%v ", i)
        }
    }
    fmt.Println("")
}

func main() {
    for i := 1; i <= 100; i++ {
        if IsPrime(i) {
            fmt.Printf("%v ", i)
        }
    }
    fmt.Println("")
    for i := 1; i <= 100; i++ {
        if IsPrimeSqrt(i) {
            fmt.Printf("%v ", i)
        }
    }
    fmt.Println("")
    SieveOfEratosthenes(100)
}

Example 2: checking for prime numbers using golang

const n = 1212121
if big.NewInt(n).ProbablyPrime(0) {
    fmt.Println(n, "is prime")
} else {
    fmt.Println(n, "is not prime")
}