Because Bob is awesome - Even my wife says so

luhn.ipynb

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                "I used the functions that I found here (Because I know Oyvind ;-) )\r\n",
                "\r\n",
                "https://communary.net/2016/02/19/the-luhn-algorithm/"
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                "# first we need to run this block to load the functions for the rest of the notebook. There will be no output \r\n",
                "function Get-LuhnChecksum {\r\n",
                "    <#\r\n",
                "        .SYNOPSIS\r\n",
                "            Calculate the Luhn checksum of a number.\r\n",
                "        .DESCRIPTION\r\n",
                "            The Luhn algorithm or Luhn formula, also known as the \"modulus 10\" or \"mod 10\" algorithm, \r\n",
                "            is a simple checksum formula used to validate a variety of identification numbers, such as \r\n",
                "            credit card numbers, IMEI numbers, National Provider Identifier numbers in the US, and \r\n",
                "            Canadian Social Insurance Numbers. It was created by IBM scientist Hans Peter Luhn.\r\n",
                "        .EXAMPLE\r\n",
                "            Get-LuhnChecksum -Number 1234567890123452\r\n",
                "            Calculate the Luch checksum of the number. The result should be 60.\r\n",
                "        .INPUTS\r\n",
                "            System.UInt64\r\n",
                "        .NOTES\r\n",
                "            Author: Øyvind Kallstad\r\n",
                "            Date: 19.02.2016\r\n",
                "            Version: 1.0\r\n",
                "            Dependencies: ConvertTo-Digits\r\n",
                "        .LINKS\r\n",
                "            https://en.wikipedia.org/wiki/Luhn_algorithm\r\n",
                "            https://communary.wordpress.com/\r\n",
                "            https://github.com/gravejester/Communary.ToolBox\r\n",
                "    #>\r\n",
                "    [CmdletBinding()]\r\n",
                "    param (\r\n",
                "        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true)]\r\n",
                "        [ValidateNotNullOrEmpty()]\r\n",
                "        [uint64] $Number\r\n",
                "    )\r\n",
                "\r\n",
                "    $digitsArray = ConvertTo-Digits -Number $Number\r\n",
                "    [array]::Reverse($digitsArray)\r\n",
                "\r\n",
                "    $sum = 0\r\n",
                "    $index = 0\r\n",
                "\r\n",
                "    foreach ($digit in $digitsArray) {\r\n",
                "        if (($index % 2) -eq 0) {\r\n",
                "            $doubledDigit = $digit * 2\r\n",
                "            if (-not($doubledDigit -eq 0)) {\r\n",
                "                $doubleDigitArray = ConvertTo-Digits -Number $doubledDigit\r\n",
                "                $sum += ($doubleDigitArray | Measure-Object -Sum | Select-Object -ExpandProperty Sum)\r\n",
                "            }\r\n",
                "        }\r\n",
                "        else {\r\n",
                "            $sum += $digit\r\n",
                "        }\r\n",
                "        $index++\r\n",
                "    }\r\n",
                "    Write-Output $sum\r\n",
                "}\r\n",
                "\r\n",
                "function New-LuhnChecksumDigit {\r\n",
                "    <#\r\n",
                "        .SYNOPSIS\r\n",
                "            Calculate the Luhn checksum digit for a number.\r\n",
                "        .DESCRIPTION\r\n",
                "            This function uses the Luhn algorithm to calculate the\r\n",
                "            Luhn checksum digit for a (partial) number.\r\n",
                "        .EXAMPLE\r\n",
                "            New-LuhnChecksumDigit -PartialNumber 123456789012345\r\n",
                "            This will get the checksum digit for the number. The result should be 2.\r\n",
                "        .INPUTS\r\n",
                "            System.UInt64\r\n",
                "        .NOTES\r\n",
                "            Author: Øyvind Kallstad\r\n",
                "            Date: 19.02.2016\r\n",
                "            Version: 1.0\r\n",
                "            Dependencies: Get-LuhnCheckSum\r\n",
                "        .LINKS\r\n",
                "            https://en.wikipedia.org/wiki/Luhn_algorithm\r\n",
                "            https://communary.wordpress.com/\r\n",
                "            https://github.com/gravejester/Communary.ToolBox\r\n",
                "    #>\r\n",
                "    [CmdletBinding()]\r\n",
                "    param (\r\n",
                "        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true)]\r\n",
                "        [uint64] $PartialNumber\r\n",
                "    )\r\n",
                "\r\n",
                "    $checksum = Get-LuhnCheckSum -Number $PartialNumber\r\n",
                "    Write-Output (($checksum * 9) % 10)\r\n",
                "}\r\n",
                "\r\n",
                "function Test-IsLuhnValid {\r\n",
                "    <#\r\n",
                "        .SYNOPSIS\r\n",
                "            Valdidate a number based on the Luhn Algorithm.\r\n",
                "        .DESCRIPTION\r\n",
                "            This function uses the Luhn algorithm to validate a number that includes\r\n",
                "            the Luhn checksum digit.\r\n",
                "        .EXAMPLE\r\n",
                "            Test-IsLuhnValid -Number 1234567890123452\r\n",
                "            This will validate whether the number is valid according to the Luhn Algorithm.\r\n",
                "        .INPUTS\r\n",
                "            System.UInt64\r\n",
                "        .OUTPUTS\r\n",
                "            System.Boolean\r\n",
                "        .NOTES\r\n",
                "            Author: Øyvind Kallstad\r\n",
                "            Date: 19.02.2016\r\n",
                "            Version: 1.0\r\n",
                "            Dependencies: Get-LuhnCheckSum, ConvertTo-Digits\r\n",
                "        .LINKS\r\n",
                "            https://en.wikipedia.org/wiki/Luhn_algorithm\r\n",
                "            https://communary.wordpress.com/\r\n",
                "            https://github.com/gravejester/Communary.ToolBox\r\n",
                "    #>\r\n",
                "    [CmdletBinding()]\r\n",
                "    param (\r\n",
                "        [Parameter(Mandatory = $true, Position = 0, ValueFromPipeline = $true)]\r\n",
                "        [uint64] $Number\r\n",
                "    )\r\n",
                "\r\n",
                "    $numberDigits = ConvertTo-Digits -Number $Number\r\n",
                "    $checksumDigit = $numberDigits[-1]\r\n",
                "    $numberWithoutChecksumDigit = $numberDigits[0..($numberDigits.Count - 2)] -join ''\r\n",
                "    $checksum = Get-LuhnCheckSum -Number $numberWithoutChecksumDigit\r\n",
                "\r\n",
                "    if ((($checksum + $checksumDigit) % 10) -eq 0) {\r\n",
                "        Write-Output $true\r\n",
                "    }\r\n",
                "    else {\r\n",
                "        Write-Output $false\r\n",
                "    }\r\n",
                "}\r\n",
                "function ConvertTo-Digits {\r\n",
                "    <#\r\n",
                "        .SYNOPSIS\r\n",
                "            Convert an integer into an array of bytes of its individual digits.\r\n",
                "        .DESCRIPTION\r\n",
                "            Convert an integer into an array of bytes of its individual digits.\r\n",
                "        .EXAMPLE\r\n",
                "            ConvertTo-Digits 145\r\n",
                "        .INPUTS\r\n",
                "            System.UInt64\r\n",
                "        .LINK\r\n",
                "            https://communary.wordpress.com/\r\n",
                "            https://github.com/gravejester/Communary.ToolBox\r\n",
                "        .NOTES\r\n",
                "            Author: Øyvind Kallstad\r\n",
                "            Date: 09.05.2015\r\n",
                "            Version: 1.0\r\n",
                "    #>\r\n",
                "    [OutputType([System.Byte[]])]\r\n",
                "    [CmdletBinding()]\r\n",
                "    param(\r\n",
                "        [Parameter(Position = 0, Mandatory = $true, ValueFromPipeline = $true)]\r\n",
                "        [uint64]$Number\r\n",
                "    )\r\n",
                "    $n = $Number\r\n",
                "    $numberOfDigits = 1 + [convert]::ToUInt64([math]::Floor(([math]::Log10($n))))\r\n",
                "    $digits = New-Object Byte[] $numberOfDigits\r\n",
                "    for ($i = ($numberOfDigits - 1); $i -ge 0; $i--) {\r\n",
                "        $digit = $n % 10\r\n",
                "        $digits[$i] = $digit\r\n",
                "        $n = [math]::Floor($n / 10)\r\n",
                "    }\r\n",
                "    Write-Output $digits\r\n",
                "}"
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            "source": [
                "With those loaded we can now run our code"
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            "source": [
                "Test-IsLuhnValid -NUmber 1114"
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    "name": "stdout",
    "text": "False\n",
    "output_type": "stream"
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            "execution_count": 8
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