Convert Roman Numerals to a Number

HCL Domino Domino Forum
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1

Anyone aware of a function or formula to convert Roman Numerals to a number?

2

There are plenty of calculators out there like this one
Roman Numeral Converter (calculatorsoup.com)

but I know of no way in Notes to convert Roman Numerals over 3999 because of the line that goes over the entire numeral that signifies that it needs to be multiplied by 1000. Otherwise, if you only need number less than 4000, it should be pretty straight forward to write.
How to Build a Roman Numeral Converter and an Interactive Roman Numerals Chart (freecodecamp.org)

3

From ChatGPT:

Function RomanToDecimal(roman As String) As Integer
Dim romanValues List As Integer
romanValues("I") = 1
romanValues("V") = 5
romanValues("X") = 10
romanValues("L") = 50
romanValues("C") = 100
romanValues("D") = 500
romanValues("M") = 1000

Dim decimalValue As Integer
Dim i As Integer

For i = 1 To Len(roman)
Dim currentSymbol As String
Dim nextSymbol As String

currentSymbol = Mid(roman, i, 1)
nextSymbol = ""

If i < Len(roman) Then
nextSymbol = Mid(roman, i + 1, 1)
End If

If romanValues(currentSymbol) < romanValues(nextSymbol) Then
decimalValue = decimalValue - romanValues(currentSymbol)
Else
decimalValue = decimalValue + romanValues(currentSymbol)
End If
Next

RomanToDecimal = decimalValue
End Function

4

Nice solution... unfortunately it will not work (like very much of the LotusScript code generated by ChatGPT) ... It will throw an error on the last character as then nextSymbol = "" and romanValues("") is not defined...

There has to be one more if around the calculation:

      If nextSymbol <> "" Then
        If romanValues(currentSymbol) < romanValues(nextSymbol) Then
            decimalValue = decimalValue - romanValues(currentSymbol)
        Else
            decimalValue = decimalValue + romanValues(currentSymbol)
        End If
    Else
        decimalValue = decimalValue + romanValues(currentSymbol)
    End If

And of course one would need to "filter out" characters that are not roman by surrounding all of this with another if:

    If IsElement( romanValues(currentSymbol) ) Then
      If nextSymbol <> "" and IsElement( romanValues(currentSymbol) ) Then
        If romanValues(currentSymbol) < romanValues(nextSymbol) Then
            decimalValue = decimalValue - romanValues(currentSymbol)
        Else
            decimalValue = decimalValue + romanValues(currentSymbol)
        End If
    Else
        decimalValue = decimalValue + romanValues(currentSymbol)
    End If
  End If

And this still fails if you have a string like IWX as it would result in 11 instead of 9.

So there is some more room for improvement....

5

This worked along with the changes @Torsten Link mentioned.

6

Hi Michael,

Is it like that your requirement is -->

1. To pass let's say some roman numerals and then Notes should fine its corresponding Integer on its own? 2. You do not wish to make Notes understand what does roman numerals really corresponds to which number by manual inputs in code etc. You want Notes to interpret it.

If yes, then there is no inbuilt API (Formula Language/LotusScript) method for same.

Regards,

Amit

7

Made a couple of adjustments to the code.

I set it up to skip the Next Roman Numeral if it is greater than the Current.

Example:
LXXXIX - the 4th X is skipped when processing the I

Dim bSkipCurrentLenCount As Boolean
Dim iListRomanValues List As Integer
Dim iLenCount As Integer, iLenCountRomNum As Integer, iDecimalValue As Integer
Dim sRomanNumeral As String, sSymbolCurrent As String, sSymbolNext As String

On Error GoTo ErrorHandler


iListRomanValues(“I”) = 1

iListRomanValues(“V”) = 5

iListRomanValues(“X”) = 10

iListRomanValues(“L”) = 50

iListRomanValues(“C”) = 100

iListRomanValues(“D”) = 500

iListRomanValues(“M”) = 1000


bSkipCurrentLenCount = False


iDecimalValue = 0


sRomanNumeral = “LXXXIX”

iLenCountRomNum = Len(sRomanNumeral)


For iLenCount = 1 To iLenCountRomNum

If bSkipCurrentLenCount = True Then

bSkipCurrentLenCount = False


            GoTo NextLenCount
    End If
   
    sSymbolCurrent = Mid(sRomanNumeral, iLenCount, 1)
    sSymbolNext = Mid(sRomanNumeral, iLenCount + 1, 1)
   
    If sSymbolNext = "" Then
            iDecimalValue = iDecimalValue + iListRomanValues(sSymbolCurrent)
    Else
            If iListRomanValues(sSymbolCurrent) &lt; iListRomanValues(sSymbolNext) Then
                    iDecimalValue = iDecimalValue + (iListRomanValues(sSymbolNext) - iListRomanValues(sSymbolCurrent))
                   
                    bSkipCurrentLenCount = True                
            Else
                    iDecimalValue = iDecimalValue + iListRomanValues(sSymbolCurrent)
            End If
    End If



NextLenCount:

Next


If iDecimalValue < 0 Then

iDecimalValue = 0

End If


GoTo ExitSub


ErrorHandler:

iDecimalValue = 0


Resume ExitSub


ExitSub:

'Exit Sub