VB Function to Format Roman Numerals

The function below can be used to convert integers into Roman numerals.

' Formats a number as a roman numeral.
' Author: Christian d'Heureuse (www.source-code.biz)
Public Function FormatRoman(ByVal n As Integer) As String
   If n = 0 Then FormatRoman = "0": Exit Function
      ' There is no roman symbol for 0, but we don't want to return an empty string.
   Const r = "IVXLCDM"              ' roman symbols
   Dim i As Integer: i = Abs(n)
   Dim s As String, p As Integer
   For p = 1 To 5 Step 2
      Dim d As Integer: d = i Mod 10: i = i \ 10
      Select Case d                 ' format a decimal digit
         Case 0 To 3: s = String(d, Mid(r, p, 1)) & s
         Case 4:      s = Mid(r, p, 2) & s
         Case 5 To 8: s = Mid(r, p + 1, 1) & String(d - 5, Mid(r, p, 1)) & s
         Case 9:      s = Mid(r, p, 1) & Mid(r, p + 2, 1) & s
         End Select
      Next
   s = String(i, "M") & s           ' format thousands
   If n < 0 Then s = "-" & s        ' insert sign if negative (non-standard)
   FormatRoman = s
   End Function

Test routine:

' Writes a list of roman numerals into a text file.
' The output can be used as a "decimal to roman" conversion table.
Public Sub PrintToFile(ByVal FileName, Optional ByVal First = 1, Optional ByVal Last = 2100)
   Dim fh: fh = FreeFile
   Open FileName For Output As fh
   Dim i As Integer
   For i = First To Last
      Print #fh, i & " = " & FormatRoman(i)
      Next
   Close #fh
   End Sub

Author: Christian d'Heureuse (www.source-code.biz, www.inventec.ch/chdh)
License: Free / LGPL
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