VBScript Scripting Techniques: Convert between decimal and Roman Numerals

In this section I'll introduce two code snippets to convert 2007 to MMVII to 2007 again.
Only "basic" VBScript is used, so this code should work in any Windows version, in stand-alone scripts, HTAs, or even ASP.

Decimal2Roman
VBScript Code:
Function Decimal2Roman( ByVal intDecimal ) ' This Function converts intDecimal to its Roman numeral value. ' Written by: Rob van der Woude, http://www.robvanderwoude.com ' ' intDecimal should be an integer in the range of 1..4999. ' ' For the Roman numeral "modern" notation is used, i.e. 1999 ' will be written as MCMXCIX, not MIM. ' ' More information on Roman numerals can be found on WikiPedia: ' http://en.wikipedia.org/wiki/Roman_numerals ' Some housekeeping Dim strRoman strRoman = "" ' First, add an "M" for every multiple of 1000 Do While intDecimal >= 1000 intDecimal = intDecimal - 1000 strRoman = strRoman & "M" Loop ' Next, add "CM" for 900, or "D" for 500, or "CD" for 400 If intDecimal >= 900 Then intDecimal = intDecimal - 900 strRoman = strRoman & "CM" ElseIf intDecimal >= 500 Then intDecimal = intDecimal - 500 strRoman = strRoman & "D" ElseIf intDecimal >= 400 Then intDecimal = intDecimal - 400 strRoman = strRoman & "CD" End If ' Add a "C" for every remaining multiple of 100 Do While intDecimal >= 100 intDecimal = intDecimal - 100 strRoman = strRoman & "C" Loop ' Add "XC" for 90, or "L" for 50, or "XL" for 40 If intDecimal >= 90 Then intDecimal = intDecimal - 90 strRoman = strRoman & "XC" ElseIf intDecimal >= 50 Then intDecimal = intDecimal - 50 strRoman = strRoman & "L" ElseIf intDecimal >= 40 Then intDecimal = intDecimal - 40 strRoman = strRoman & "XL" End If ' Add an "X" for every remaining multiple of 10 Do While intDecimal >= 10 intDecimal = intDecimal - 10 strRoman = strRoman & "X" Loop ' Add "IX" for 9, or "V" for 5, or "IV" for 4 If intDecimal >= 9 Then intDecimal = intDecimal - 9 strRoman = strRoman & "IX" ElseIf intDecimal >= 5 Then intDecimal = intDecimal - 5 strRoman = strRoman & "V" ElseIf intDecimal >= 4 Then intDecimal = intDecimal - 4 strRoman = strRoman & "IV" End If ' Finally, add an "I" for every remaining multiple of 1 Do While intDecimal >= 1 intDecimal = intDecimal - 1 strRoman = strRoman & "I" Loop ' Return the result Decimal2Roman = strRoman End Function
Requirements:
Windows version:	any
Network:	N/A
Client software:	N/A
Script Engine:	any
Summarized:	Works in any Windows version, with any scripting engine.

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Roman2Decimal
VBScript Code:
Function Roman2Decimal( ByVal strRoman ) ' This Function converts strRoman to its decimal numerical value. ' Written by: Rob van der Woude, http://www.robvanderwoude.com ' ' Roman numerals "old style" will still be converted correctly ' into decimal numbers. However, numerals like "MIIIM" for 1997 ' would be invalid in any notation, and consequently will ' return invalid results. ' ' More information on Roman numerals can be found on WikiPedia: ' http://en.wikipedia.org/wiki/Roman_numerals ' Some housekeeping Dim arrRoman( ), intRoman ReDim arrRoman( Len( strRoman ) -1 ) intRoman = 0 ' Store each "digit" of the Roman numeral in an array For i = 0 To UBound( arrRoman ) arrRoman( i ) = Mid( strRoman, i + 1, 1 ) Next ' Then convert each "digit" to its numeric value For i = 0 To UBound( arrRoman ) Select Case arrRoman( i ) Case "M" arrRoman( i ) = 1000 Case "D" arrRoman( i ) = 500 Case "C" arrRoman( i ) = 100 Case "L" arrRoman( i ) = 50 Case "X" arrRoman( i ) = 10 Case "V" arrRoman( i ) = 5 Case "I" arrRoman( i ) = 1 End Select Next ' Now comes the hard part: for each "digit" decide if it will be ' added or subtracted, based on the value of the following "digit" For i = 0 To UBound( arrRoman ) - 1 If arrRoman( i ) < arrRoman( i + 1 ) Then ' E.g. "I" in "IX" (9): subtract 1 intRoman = intRoman - arrRoman( i ) ElseIf arrRoman( i ) = arrRoman( i + 1 ) Then ' E.g. "I" in "XII" (12), "III" (3) or in "IIX" (ancient notation for 8). ' The latter should actually be "VIII" in "modern" roman numerals, but ' "IIX" was used in ancient times, so let's just be prepared. ' We'll add the value to the next position in the array, so it will be ' reevaluated in the next iteration of the loop. ' Note: this trick will definitely fail on invalid notations like "IIIX". arrRoman( i + 1 ) = arrRoman( i ) + arrRoman( i + 1 ) arrRoman( i ) = 0 Else ' arrRoman( i ) > arrRoman( i + 1 ) ' E.g. "V" in "XV" (15): add 5 intRoman = intRoman + arrRoman( i ) End If Next ' The last "digit" doesn't have a following "digit" so it ' can, be added without having to test a following "digit" intRoman= intRoman + arrRoman( UBound( arrRoman ) ) ' Return the calculated value Roman2Decimal = intRoman End Function Sub Syntax( ByVal strErr ) If strErr <> "" Then strMsg = vbCrLf & strErr & vbCrLf & vbCrLf Else strMsg = vbCrLf End If strMsg = strMsg _ & "Romans.vbs, Version 1.01" & vbCrLf _ & "Convert between Roman and decimal numerals." & vbCrLf & vbCrLf _ & "Usage: ROMANS.VBS numeral" & vbCrLf & vbCrLf _ & "Where: ""numeral"" is either a (decimal) integer in the" & vbCrLf _ & " range of 1..4999, or a Roman numeral." & vbCrLf & vbCrLf _ & "Notes: [1] Returned Roman numerals follow ""modern"" conventions," & vbCrLf _ & " i.e. 1999 will be written as ""MCMXCIX"" instead of ""MIM""." & vbCrLf _ & " However, these Roman numerals ""old style"" will still be" & vbCrLf _ & " converted correctly into decimal numbers." & vbCrLf _ & " Numerals like ""MIIIM"" for 1997 would be invalid in any" & vbCrLf _ & " notation, and consequently will return invalid results." & vbCrLf _ & " [2] More information on Roman numerals can be found on WikiPedia:" & vbCrLf _ & " http://en.wikipedia.org/wiki/Roman_numerals" & vbCrLf & vbCrLf _ & "Written by Rob van der Woude" & vbCrLf _ & "http://www.robvanderwoude.com" WScript.Echo strMsg WScript.Quit( 1 ) End Sub
Requirements:
Windows version:	any
Network:	N/A
Client software:	N/A
Script Engine:	any
Summarized:	Works in any Windows version, with any scripting engine.

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Convert decimal numbers to Roman Numerals vv.