Functions/ConvertFrom-RomanNumeral.ps1
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function ConvertFrom-RomanNumeral { <# .SYNOPSIS Converts a roman numeral to a number. .DESCRIPTION Converts a roman numeral - in the range of I..MMMCMXCIX - to a number. .PARAMETER Numeral A roman numeral in the range I..MMMCMXCIX (1..3,999). .PARAMETER IncludeInput Switch to include input values in the output .INPUTS System.String[] .OUTPUTS System.Int32 .NOTES Requires PowerShell version 3.0 .EXAMPLE ConvertFrom-RomanNumeral -Numeral MMXIV .EXAMPLE "MMXIV" | ConvertFrom-RomanNumeral #> [CmdletBinding()] [OutputType([int])] Param ( [Parameter(Mandatory = $true, HelpMessage = 'Enter a roman numeral in the range I..MMMCMXCIX', ValueFromPipeline = $true, Position = 0)] [ValidatePattern('(?x)^ M{0,3} # Thousands (CM|CD|D?C{0,3}) # Hundreds (XC|XL|L?X{0,3}) # Tens (IX|IV|V?I{0,3}) # Ones $')] [string[]] $Numeral, [switch] $IncludeInput ) begin { Write-Verbose -Message "Starting [$($MyInvocation.Mycommand)]" # This must be an [ordered] hashtable $RomanToDecimal = [ordered]@{ M = 1000 CM = 900 D = 500 CD = 400 C = 100 XC = 90 L = 50 X = 10 IX = 9 V = 5 IV = 4 I = 1 } } process { foreach ($curNum in $Numeral) { $roman = $curNum + '$' $value = 0 do { foreach ($key in $RomanToDecimal.Keys) { if ($key.Length -eq 1) { if ($key -match $roman.Substring(0, 1)) { $value += $RomanToDecimal.$key $roman = $roman.Substring(1) break } } else { if ($key -match $roman.Substring(0, 2)) { $value += $RomanToDecimal.$key $roman = $roman.Substring(2) break } } } } until ($roman -eq '$') if ($IncludeInput) { New-Object -TypeName psobject -Property ([ordered] @{ RomanNumeral = $curNum Number = $value }) # write-output 'blah' } else { $value } } } end { Write-Verbose -Message "Ending [$($MyInvocation.Mycommand)]" } } |