prime.go

package main

import (
	"fmt"
	"time"
)

func main() {
	start := time.Now()
	_ = p0(200_000)
	fmt.Printf("The original: %v ms\n", time.Since(start).Milliseconds())

	start = time.Now()
	_ = p1(200_000)
	fmt.Printf("Without slice (int): %v ms\n", time.Since(start).Milliseconds())

	start = time.Now()
	_ = p2(int32(200_000))
	fmt.Printf("Without slice (int32) %v ms\n", time.Since(start).Milliseconds())
}

func p0(limit int) int {
	var lastPrime int
	primes := []int{}
	for x := 2; x < limit; x++ {
		is_prime := true
		for y := 2; y < x; y++ {
			if x%y == 0 {
				is_prime = false
				break
			}
		}
		if is_prime {
			primes = append(primes, x)
			lastPrime = x
		}
	}
	return lastPrime
}

func p1(limit int) int {
	var lastPrime int
	for x := 2; x < limit; x++ {
		isPrime := true
		for y := 2; y < x; y++ {
			if x%y == 0 {
				isPrime = false
				break
			}
		}
		if isPrime {
			lastPrime = x
		}
	}
	return lastPrime
}

func p2(limit int32) int32 {
	var lastPrime int32
	var x, y int32
	for x = 2; x < limit; x++ {
		isPrime := true
		for y = 2; y < x; y++ {
			if x%y == 0 {
				isPrime = false
				break
			}
		}
		if isPrime {
			lastPrime = x
		}
	}
	return lastPrime
}