kazuyamaa/multi-language-messages-01 huggingface dataset:
Task: Luhn test of credit card numbers
C: #include <string.h>
#include <stdio.h>

int luhn(const char* cc)
{
	const int m[] = {0,2,4,6,8,1,3,5,7,9}; 
	int i, odd = 1, sum = 0;

	for (i = strlen(cc); i--; odd = !odd) {
		int digit = cc[i] - '0';
		sum += odd ? digit : m[digit];
	}

	return sum % 10 == 0;
}

int main()
{
	const char* cc[] = {
		"49927398716",
		"49927398717",
		"1234567812345678",
		"1234567812345670",
		0
	};
	int i;

	for (i = 0; cc[i]; i++)
		printf("%16s\t%s\n", cc[i], luhn(cc[i]) ? "ok" : "not ok");

	return 0;
}

VB: Option Explicit

Sub Main()
  Debug.Print "Number 49927398716 is "; Luhn("49927398716")
  Debug.Print "Number 49927398717 is "; Luhn("49927398717")
  Debug.Print "Number 1234567812345678 is "; Luhn("1234567812345678")
  Debug.Print "Number 1234567812345670 is "; Luhn("1234567812345670")
End Sub
Private Function Luhn(Nb As String) As String
Dim t$, i&, Summ&, s&
    t = StrReverse(Nb)
    For i = 1 To Len(t) Step 2
        Summ = Summ + CInt(Mid(t, i, 1))
    Next i
    For i = 2 To Len(t) Step 2
        s = 2 * (CInt(Mid(t, i, 1)))
        If s >= 10 Then
            Summ = Summ - 9
        End If
        Summ = Summ + s
    Next i
    If Summ Mod 10 = 0 Then
        Luhn = "valid"
    Else
        Luhn = "invalid"
    End If
End Function
Task: Luhn test of credit card numbers
C#:     public static class Luhn
    {
        public static bool LuhnCheck(this string cardNumber)
        {
            return LuhnCheck(cardNumber.Select(c => c - '0').ToArray());
        }

        private static bool LuhnCheck(this int[] digits)
        {
            return GetCheckValue(digits) == 0;
        }

        private static int GetCheckValue(int[] digits)
        {
            return digits.Select((d, i) => i % 2 == digits.Length % 2 ? ((2 * d) % 10) + d / 5 : d).Sum() % 10;
        }
    }

    public static class TestProgram
    {
        public static void Main()
        {
            long[] testNumbers = {49927398716, 49927398717, 1234567812345678, 1234567812345670};
            foreach (var testNumber in testNumbers)
                Console.WriteLine("{0} is {1}valid", testNumber, testNumber.ToString().LuhnCheck() ? "" : "not ");
        }
    }

C++: #include <iostream>
using namespace std;

int toInt(const char c)
{
    return c-'0';
}

int confirm( const char *id)
{
    bool is_odd_dgt = true;
    int s = 0;
    const char *cp;

    for(cp=id; *cp; cp++);
    while(cp > id) {
        --cp;
        int k = toInt(*cp);
        if (is_odd_dgt) {
            s += k;
        }
        else {
            s += (k!=9)? (2*k)%9 : 9;
        }
	is_odd_dgt = !is_odd_dgt;
    }
    return 0 == s%10;
}

int main( )
{
    const char * t_cases[] = {
        "49927398716",
        "49927398717",
        "1234567812345678",
        "1234567812345670",
        NULL,
    };
    for ( const char **cp = t_cases; *cp; cp++) {
        cout << *cp << ": " << confirm(*cp) << endl;
    }
    return 0;
}
Task: Luhn test of credit card numbers
C++: #include <iostream>
using namespace std;

int toInt(const char c)
{
    return c-'0';
}

int confirm( const char *id)
{
    bool is_odd_dgt = true;
    int s = 0;
    const char *cp;

    for(cp=id; *cp; cp++);
    while(cp > id) {
        --cp;
        int k = toInt(*cp);
        if (is_odd_dgt) {
            s += k;
        }
        else {
            s += (k!=9)? (2*k)%9 : 9;
        }
	is_odd_dgt = !is_odd_dgt;
    }
    return 0 == s%10;
}

int main( )
{
    const char * t_cases[] = {
        "49927398716",
        "49927398717",
        "1234567812345678",
        "1234567812345670",
        NULL,
    };
    for ( const char **cp = t_cases; *cp; cp++) {
        cout << *cp << ": " << confirm(*cp) << endl;
    }
    return 0;
}

Java: public class Luhn {
    public static void main(String[] args) {
        System.out.println(luhnTest("49927398716"));
        System.out.println(luhnTest("49927398717"));
        System.out.println(luhnTest("1234567812345678"));
        System.out.println(luhnTest("1234567812345670"));
    }
    
    public static boolean luhnTest(String number){
        int s1 = 0, s2 = 0;
        String reverse = new StringBuffer(number).reverse().toString();
        for(int i = 0 ;i < reverse.length();i++){
            int digit = Character.digit(reverse.charAt(i), 10);
            if(i % 2 == 0){
                s1 += digit;
            }else{
                s2 += 2 * digit;
                if(digit >= 5){
                    s2 -= 9;
                }
            }
        }
        return (s1 + s2) % 10 == 0;
    }
}
Task: Luhn test of credit card numbers
C++: #include <iostream>
using namespace std;

int toInt(const char c)
{
    return c-'0';
}

int confirm( const char *id)
{
    bool is_odd_dgt = true;
    int s = 0;
    const char *cp;

    for(cp=id; *cp; cp++);
    while(cp > id) {
        --cp;
        int k = toInt(*cp);
        if (is_odd_dgt) {
            s += k;
        }
        else {
            s += (k!=9)? (2*k)%9 : 9;
        }
	is_odd_dgt = !is_odd_dgt;
    }
    return 0 == s%10;
}

int main( )
{
    const char * t_cases[] = {
        "49927398716",
        "49927398717",
        "1234567812345678",
        "1234567812345670",
        NULL,
    };
    for ( const char **cp = t_cases; *cp; cp++) {
        cout << *cp << ": " << confirm(*cp) << endl;
    }
    return 0;
}

Python: >>> def luhn(n):
	r = [int(ch) for ch in str(n)][::-1]
	return (sum(r[0::2]) + sum(sum(divmod(d*2,10)) for d in r[1::2])) % 10 == 0

>>> for n in (49927398716, 49927398717, 1234567812345678, 1234567812345670):
	print(n, luhn(n))
Task: Luhn test of credit card numbers
C++: #include <iostream>
using namespace std;

int toInt(const char c)
{
    return c-'0';
}

int confirm( const char *id)
{
    bool is_odd_dgt = true;
    int s = 0;
    const char *cp;

    for(cp=id; *cp; cp++);
    while(cp > id) {
        --cp;
        int k = toInt(*cp);
        if (is_odd_dgt) {
            s += k;
        }
        else {
            s += (k!=9)? (2*k)%9 : 9;
        }
	is_odd_dgt = !is_odd_dgt;
    }
    return 0 == s%10;
}

int main( )
{
    const char * t_cases[] = {
        "49927398716",
        "49927398717",
        "1234567812345678",
        "1234567812345670",
        NULL,
    };
    for ( const char **cp = t_cases; *cp; cp++) {
        cout << *cp << ": " << confirm(*cp) << endl;
    }
    return 0;
}

VB: Option Explicit

Sub Main()
  Debug.Print "Number 49927398716 is "; Luhn("49927398716")
  Debug.Print "Number 49927398717 is "; Luhn("49927398717")
  Debug.Print "Number 1234567812345678 is "; Luhn("1234567812345678")
  Debug.Print "Number 1234567812345670 is "; Luhn("1234567812345670")
End Sub
Private Function Luhn(Nb As String) As String
Dim t$, i&, Summ&, s&
    t = StrReverse(Nb)
    For i = 1 To Len(t) Step 2
        Summ = Summ + CInt(Mid(t, i, 1))
    Next i
    For i = 2 To Len(t) Step 2
        s = 2 * (CInt(Mid(t, i, 1)))
        If s >= 10 Then
            Summ = Summ - 9
        End If
        Summ = Summ + s
    Next i
    If Summ Mod 10 = 0 Then
        Luhn = "valid"
    Else
        Luhn = "invalid"
    End If
End Function
Task: Luhn test of credit card numbers
C#:     public static class Luhn
    {
        public static bool LuhnCheck(this string cardNumber)
        {
            return LuhnCheck(cardNumber.Select(c => c - '0').ToArray());
        }

        private static bool LuhnCheck(this int[] digits)
        {
            return GetCheckValue(digits) == 0;
        }

        private static int GetCheckValue(int[] digits)
        {
            return digits.Select((d, i) => i % 2 == digits.Length % 2 ? ((2 * d) % 10) + d / 5 : d).Sum() % 10;
        }
    }

    public static class TestProgram
    {
        public static void Main()
        {
            long[] testNumbers = {49927398716, 49927398717, 1234567812345678, 1234567812345670};
            foreach (var testNumber in testNumbers)
                Console.WriteLine("{0} is {1}valid", testNumber, testNumber.ToString().LuhnCheck() ? "" : "not ");
        }
    }

Go: package main

import (
    "fmt"
    "strings"
)

const input = `49927398716
49927398717
1234567812345678
1234567812345670`

var t = [...]int{0, 2, 4, 6, 8, 1, 3, 5, 7, 9}

func luhn(s string) bool {
    odd := len(s) & 1
    var sum int
    for i, c := range s {
        if c < '0' || c > '9' {
            return false
        }
        if i&1 == odd {
            sum += t[c-'0']
        } else {
            sum += int(c - '0')
        }
    }
    return sum%10 == 0
}

func main() {
    for _, s := range strings.Split(input, "\n") {
        fmt.Println(s, luhn(s))
    }
}
Task: Luhn test of credit card numbers
C#:     public static class Luhn
    {
        public static bool LuhnCheck(this string cardNumber)
        {
            return LuhnCheck(cardNumber.Select(c => c - '0').ToArray());
        }

        private static bool LuhnCheck(this int[] digits)
        {
            return GetCheckValue(digits) == 0;
        }

        private static int GetCheckValue(int[] digits)
        {
            return digits.Select((d, i) => i % 2 == digits.Length % 2 ? ((2 * d) % 10) + d / 5 : d).Sum() % 10;
        }
    }

    public static class TestProgram
    {
        public static void Main()
        {
            long[] testNumbers = {49927398716, 49927398717, 1234567812345678, 1234567812345670};
            foreach (var testNumber in testNumbers)
                Console.WriteLine("{0} is {1}valid", testNumber, testNumber.ToString().LuhnCheck() ? "" : "not ");
        }
    }

Python: >>> def luhn(n):
	r = [int(ch) for ch in str(n)][::-1]
	return (sum(r[0::2]) + sum(sum(divmod(d*2,10)) for d in r[1::2])) % 10 == 0

>>> for n in (49927398716, 49927398717, 1234567812345678, 1234567812345670):
	print(n, luhn(n))
Task: Luhn test of credit card numbers
C#:     public static class Luhn
    {
        public static bool LuhnCheck(this string cardNumber)
        {
            return LuhnCheck(cardNumber.Select(c => c - '0').ToArray());
        }

        private static bool LuhnCheck(this int[] digits)
        {
            return GetCheckValue(digits) == 0;
        }

        private static int GetCheckValue(int[] digits)
        {
            return digits.Select((d, i) => i % 2 == digits.Length % 2 ? ((2 * d) % 10) + d / 5 : d).Sum() % 10;
        }
    }

    public static class TestProgram
    {
        public static void Main()
        {
            long[] testNumbers = {49927398716, 49927398717, 1234567812345678, 1234567812345670};
            foreach (var testNumber in testNumbers)
                Console.WriteLine("{0} is {1}valid", testNumber, testNumber.ToString().LuhnCheck() ? "" : "not ");
        }
    }

VB: Option Explicit

Sub Main()
  Debug.Print "Number 49927398716 is "; Luhn("49927398716")
  Debug.Print "Number 49927398717 is "; Luhn("49927398717")
  Debug.Print "Number 1234567812345678 is "; Luhn("1234567812345678")
  Debug.Print "Number 1234567812345670 is "; Luhn("1234567812345670")
End Sub
Private Function Luhn(Nb As String) As String
Dim t$, i&, Summ&, s&
    t = StrReverse(Nb)
    For i = 1 To Len(t) Step 2
        Summ = Summ + CInt(Mid(t, i, 1))
    Next i
    For i = 2 To Len(t) Step 2
        s = 2 * (CInt(Mid(t, i, 1)))
        If s >= 10 Then
            Summ = Summ - 9
        End If
        Summ = Summ + s
    Next i
    If Summ Mod 10 = 0 Then
        Luhn = "valid"
    Else
        Luhn = "invalid"
    End If
End Function
Task: Luhn test of credit card numbers
Java: public class Luhn {
    public static void main(String[] args) {
        System.out.println(luhnTest("49927398716"));
        System.out.println(luhnTest("49927398717"));
        System.out.println(luhnTest("1234567812345678"));
        System.out.println(luhnTest("1234567812345670"));
    }
    
    public static boolean luhnTest(String number){
        int s1 = 0, s2 = 0;
        String reverse = new StringBuffer(number).reverse().toString();
        for(int i = 0 ;i < reverse.length();i++){
            int digit = Character.digit(reverse.charAt(i), 10);
            if(i % 2 == 0){
                s1 += digit;
            }else{
                s2 += 2 * digit;
                if(digit >= 5){
                    s2 -= 9;
                }
            }
        }
        return (s1 + s2) % 10 == 0;
    }
}

Python: >>> def luhn(n):
	r = [int(ch) for ch in str(n)][::-1]
	return (sum(r[0::2]) + sum(sum(divmod(d*2,10)) for d in r[1::2])) % 10 == 0

>>> for n in (49927398716, 49927398717, 1234567812345678, 1234567812345670):
	print(n, luhn(n))
Task: Luhn test of credit card numbers
Go: package main

import (
    "fmt"
    "strings"
)

const input = `49927398716
49927398717
1234567812345678
1234567812345670`

var t = [...]int{0, 2, 4, 6, 8, 1, 3, 5, 7, 9}

func luhn(s string) bool {
    odd := len(s) & 1
    var sum int
    for i, c := range s {
        if c < '0' || c > '9' {
            return false
        }
        if i&1 == odd {
            sum += t[c-'0']
        } else {
            sum += int(c - '0')
        }
    }
    return sum%10 == 0
}

func main() {
    for _, s := range strings.Split(input, "\n") {
        fmt.Println(s, luhn(s))
    }
}

Python: >>> def luhn(n):
	r = [int(ch) for ch in str(n)][::-1]
	return (sum(r[0::2]) + sum(sum(divmod(d*2,10)) for d in r[1::2])) % 10 == 0

>>> for n in (49927398716, 49927398717, 1234567812345678, 1234567812345670):
	print(n, luhn(n))
Task: Luhn test of credit card numbers
Go: package main

import (
    "fmt"
    "strings"
)

const input = `49927398716
49927398717
1234567812345678
1234567812345670`

var t = [...]int{0, 2, 4, 6, 8, 1, 3, 5, 7, 9}

func luhn(s string) bool {
    odd := len(s) & 1
    var sum int
    for i, c := range s {
        if c < '0' || c > '9' {
            return false
        }
        if i&1 == odd {
            sum += t[c-'0']
        } else {
            sum += int(c - '0')
        }
    }
    return sum%10 == 0
}

func main() {
    for _, s := range strings.Split(input, "\n") {
        fmt.Println(s, luhn(s))
    }
}

VB: Option Explicit

Sub Main()
  Debug.Print "Number 49927398716 is "; Luhn("49927398716")
  Debug.Print "Number 49927398717 is "; Luhn("49927398717")
  Debug.Print "Number 1234567812345678 is "; Luhn("1234567812345678")
  Debug.Print "Number 1234567812345670 is "; Luhn("1234567812345670")
End Sub
Private Function Luhn(Nb As String) As String
Dim t$, i&, Summ&, s&
    t = StrReverse(Nb)
    For i = 1 To Len(t) Step 2
        Summ = Summ + CInt(Mid(t, i, 1))
    Next i
    For i = 2 To Len(t) Step 2
        s = 2 * (CInt(Mid(t, i, 1)))
        If s >= 10 Then
            Summ = Summ - 9
        End If
        Summ = Summ + s
    Next i
    If Summ Mod 10 = 0 Then
        Luhn = "valid"
    Else
        Luhn = "invalid"
    End If
End Function
Task: Luhn test of credit card numbers
Python: >>> def luhn(n):
	r = [int(ch) for ch in str(n)][::-1]
	return (sum(r[0::2]) + sum(sum(divmod(d*2,10)) for d in r[1::2])) % 10 == 0

>>> for n in (49927398716, 49927398717, 1234567812345678, 1234567812345670):
	print(n, luhn(n))

VB: Option Explicit

Sub Main()
  Debug.Print "Number 49927398716 is "; Luhn("49927398716")
  Debug.Print "Number 49927398717 is "; Luhn("49927398717")
  Debug.Print "Number 1234567812345678 is "; Luhn("1234567812345678")
  Debug.Print "Number 1234567812345670 is "; Luhn("1234567812345670")
End Sub
Private Function Luhn(Nb As String) As String
Dim t$, i&, Summ&, s&
    t = StrReverse(Nb)
    For i = 1 To Len(t) Step 2
        Summ = Summ + CInt(Mid(t, i, 1))
    Next i
    For i = 2 To Len(t) Step 2
        s = 2 * (CInt(Mid(t, i, 1)))
        If s >= 10 Then
            Summ = Summ - 9
        End If
        Summ = Summ + s
    Next i
    If Summ Mod 10 = 0 Then
        Luhn = "valid"
    Else
        Luhn = "invalid"
    End If
End Function
Task: Luhn test of credit card numbers
Java: public class Luhn {
    public static void main(String[] args) {
        System.out.println(luhnTest("49927398716"));
        System.out.println(luhnTest("49927398717"));
        System.out.println(luhnTest("1234567812345678"));
        System.out.println(luhnTest("1234567812345670"));
    }
    
    public static boolean luhnTest(String number){
        int s1 = 0, s2 = 0;
        String reverse = new StringBuffer(number).reverse().toString();
        for(int i = 0 ;i < reverse.length();i++){
            int digit = Character.digit(reverse.charAt(i), 10);
            if(i % 2 == 0){
                s1 += digit;
            }else{
                s2 += 2 * digit;
                if(digit >= 5){
                    s2 -= 9;
                }
            }
        }
        return (s1 + s2) % 10 == 0;
    }
}

VB: Option Explicit

Sub Main()
  Debug.Print "Number 49927398716 is "; Luhn("49927398716")
  Debug.Print "Number 49927398717 is "; Luhn("49927398717")
  Debug.Print "Number 1234567812345678 is "; Luhn("1234567812345678")
  Debug.Print "Number 1234567812345670 is "; Luhn("1234567812345670")
End Sub
Private Function Luhn(Nb As String) As String
Dim t$, i&, Summ&, s&
    t = StrReverse(Nb)
    For i = 1 To Len(t) Step 2
        Summ = Summ + CInt(Mid(t, i, 1))
    Next i
    For i = 2 To Len(t) Step 2
        s = 2 * (CInt(Mid(t, i, 1)))
        If s >= 10 Then
            Summ = Summ - 9
        End If
        Summ = Summ + s
    Next i
    If Summ Mod 10 = 0 Then
        Luhn = "valid"
    Else
        Luhn = "invalid"
    End If
End Function
Task: Luhn test of credit card numbers
C++: #include <iostream>
using namespace std;

int toInt(const char c)
{
    return c-'0';
}

int confirm( const char *id)
{
    bool is_odd_dgt = true;
    int s = 0;
    const char *cp;

    for(cp=id; *cp; cp++);
    while(cp > id) {
        --cp;
        int k = toInt(*cp);
        if (is_odd_dgt) {
            s += k;
        }
        else {
            s += (k!=9)? (2*k)%9 : 9;
        }
	is_odd_dgt = !is_odd_dgt;
    }
    return 0 == s%10;
}

int main( )
{
    const char * t_cases[] = {
        "49927398716",
        "49927398717",
        "1234567812345678",
        "1234567812345670",
        NULL,
    };
    for ( const char **cp = t_cases; *cp; cp++) {
        cout << *cp << ": " << confirm(*cp) << endl;
    }
    return 0;
}

Go: package main

import (
    "fmt"
    "strings"
)

const input = `49927398716
49927398717
1234567812345678
1234567812345670`

var t = [...]int{0, 2, 4, 6, 8, 1, 3, 5, 7, 9}

func luhn(s string) bool {
    odd := len(s) & 1
    var sum int
    for i, c := range s {
        if c < '0' || c > '9' {
            return false
        }
        if i&1 == odd {
            sum += t[c-'0']
        } else {
            sum += int(c - '0')
        }
    }
    return sum%10 == 0
}

func main() {
    for _, s := range strings.Split(input, "\n") {
        fmt.Println(s, luhn(s))
    }
}
Task: Luhn test of credit card numbers
C#:     public static class Luhn
    {
        public static bool LuhnCheck(this string cardNumber)
        {
            return LuhnCheck(cardNumber.Select(c => c - '0').ToArray());
        }

        private static bool LuhnCheck(this int[] digits)
        {
            return GetCheckValue(digits) == 0;
        }

        private static int GetCheckValue(int[] digits)
        {
            return digits.Select((d, i) => i % 2 == digits.Length % 2 ? ((2 * d) % 10) + d / 5 : d).Sum() % 10;
        }
    }

    public static class TestProgram
    {
        public static void Main()
        {
            long[] testNumbers = {49927398716, 49927398717, 1234567812345678, 1234567812345670};
            foreach (var testNumber in testNumbers)
                Console.WriteLine("{0} is {1}valid", testNumber, testNumber.ToString().LuhnCheck() ? "" : "not ");
        }
    }

Java: public class Luhn {
    public static void main(String[] args) {
        System.out.println(luhnTest("49927398716"));
        System.out.println(luhnTest("49927398717"));
        System.out.println(luhnTest("1234567812345678"));
        System.out.println(luhnTest("1234567812345670"));
    }
    
    public static boolean luhnTest(String number){
        int s1 = 0, s2 = 0;
        String reverse = new StringBuffer(number).reverse().toString();
        for(int i = 0 ;i < reverse.length();i++){
            int digit = Character.digit(reverse.charAt(i), 10);
            if(i % 2 == 0){
                s1 += digit;
            }else{
                s2 += 2 * digit;
                if(digit >= 5){
                    s2 -= 9;
                }
            }
        }
        return (s1 + s2) % 10 == 0;
    }
}
Task: Luhn test of credit card numbers
Go: package main

import (
    "fmt"
    "strings"
)

const input = `49927398716
49927398717
1234567812345678
1234567812345670`

var t = [...]int{0, 2, 4, 6, 8, 1, 3, 5, 7, 9}

func luhn(s string) bool {
    odd := len(s) & 1
    var sum int
    for i, c := range s {
        if c < '0' || c > '9' {
            return false
        }
        if i&1 == odd {
            sum += t[c-'0']
        } else {
            sum += int(c - '0')
        }
    }
    return sum%10 == 0
}

func main() {
    for _, s := range strings.Split(input, "\n") {
        fmt.Println(s, luhn(s))
    }
}

Java: public class Luhn {
    public static void main(String[] args) {
        System.out.println(luhnTest("49927398716"));
        System.out.println(luhnTest("49927398717"));
        System.out.println(luhnTest("1234567812345678"));
        System.out.println(luhnTest("1234567812345670"));
    }
    
    public static boolean luhnTest(String number){
        int s1 = 0, s2 = 0;
        String reverse = new StringBuffer(number).reverse().toString();
        for(int i = 0 ;i < reverse.length();i++){
            int digit = Character.digit(reverse.charAt(i), 10);
            if(i % 2 == 0){
                s1 += digit;
            }else{
                s2 += 2 * digit;
                if(digit >= 5){
                    s2 -= 9;
                }
            }
        }
        return (s1 + s2) % 10 == 0;
    }
}
Task: Luhn test of credit card numbers
C: #include <string.h>
#include <stdio.h>

int luhn(const char* cc)
{
	const int m[] = {0,2,4,6,8,1,3,5,7,9}; 
	int i, odd = 1, sum = 0;

	for (i = strlen(cc); i--; odd = !odd) {
		int digit = cc[i] - '0';
		sum += odd ? digit : m[digit];
	}

	return sum % 10 == 0;
}

int main()
{
	const char* cc[] = {
		"49927398716",
		"49927398717",
		"1234567812345678",
		"1234567812345670",
		0
	};
	int i;

	for (i = 0; cc[i]; i++)
		printf("%16s\t%s\n", cc[i], luhn(cc[i]) ? "ok" : "not ok");

	return 0;
}

PHP: $numbers = "49927398716 49927398717 1234567812345678 1234567812345670";
foreach (split(' ', $numbers) as $n)
    echo "$n is ", luhnTest($n) ? 'valid' : 'not valid', '</br>';

function luhnTest($num) {
    $len = strlen($num);
    for ($i = $len-1; $i >= 0; $i--) {
        $ord = ord($num[$i]);
        if (($len - 1) & $i) {
            $sum += $ord;
        } else {
            $sum += $ord / 5 + (2 * $ord) % 10;
        }
    }       
    return $sum % 10 == 0;
}
Task: Luhn test of credit card numbers
C#:     public static class Luhn
    {
        public static bool LuhnCheck(this string cardNumber)
        {
            return LuhnCheck(cardNumber.Select(c => c - '0').ToArray());
        }

        private static bool LuhnCheck(this int[] digits)
        {
            return GetCheckValue(digits) == 0;
        }

        private static int GetCheckValue(int[] digits)
        {
            return digits.Select((d, i) => i % 2 == digits.Length % 2 ? ((2 * d) % 10) + d / 5 : d).Sum() % 10;
        }
    }

    public static class TestProgram
    {
        public static void Main()
        {
            long[] testNumbers = {49927398716, 49927398717, 1234567812345678, 1234567812345670};
            foreach (var testNumber in testNumbers)
                Console.WriteLine("{0} is {1}valid", testNumber, testNumber.ToString().LuhnCheck() ? "" : "not ");
        }
    }

PHP: $numbers = "49927398716 49927398717 1234567812345678 1234567812345670";
foreach (split(' ', $numbers) as $n)
    echo "$n is ", luhnTest($n) ? 'valid' : 'not valid', '</br>';

function luhnTest($num) {
    $len = strlen($num);
    for ($i = $len-1; $i >= 0; $i--) {
        $ord = ord($num[$i]);
        if (($len - 1) & $i) {
            $sum += $ord;
        } else {
            $sum += $ord / 5 + (2 * $ord) % 10;
        }
    }       
    return $sum % 10 == 0;
}