Golang golang-isbn (snippet)

Go programming example 'golang-isbn'

golang-isbn

Golang beginners example: golang-isbn

package main

import (
    "fmt"
    "os"
    "strings"
)

func main() {
    isbnInput := os.Args[1]
    isbnClean := strings.Replace(isbnInput, "-", "", -1)
    fmt.Printf("ISBN verification of %v: %v\n", isbnInput, VerifyISBN(isbnClean))
}

func isNotNumber(n rune) bool {
    return n < '0' || '9' < n
}

func VerifyISBN(code string) bool {
    if len(code) == 10 {
        return VerifyISBN10(code)
    } else if len(code) == 13 {
        return VerifyISBN13(code)
    } else {
        return false
    }
}

func VerifyISBN10(code string) bool {

    if len(code) != 10 {
        return false
    }

    sum, multiply := 0, 10
    for _, n := range code {

        var d int
        switch {
        case n == 'X':
            d = 10
        case isNotNumber(n):
            return false
        default:
            d = int(n - '0')
        }

        sum += multiply * d
        multiply--
    }

    return sum%11 == 0
}

func VerifyISBN13(code string) bool {

    if len(code) != 13 {
        return false
    }

    sum, weight := 0, 1
    for _, n := range code[:len(code)-1] {
        if isNotNumber(n) {
            return false
        }
        sum += int(n-'0') * weight
        if weight == 1 {
            weight = 3
        } else {
            weight = 1
        }
    }

    d := 10 - sum%10
    if d == 10 {
        d = 0
    }

    return d == int(code[len(code)-1]-'0')
}

Useful links

• Learn Go: https://golangr.com
• Download Go: https://golang.org