"Standard" syntax for Roman Numerals seem to always show 45 = XLV.
I wrote a little program to convert roman numerals to integers, so I started wondering what is valid in subtractive notation and what isn't. For example, 495 is much shorter as VD rather than CDXCV
Are only some characters (I,X,C) considered valid in Subtractive notation?
Are our conclusions based on specific historical instructions, or just lack of certain kinds of examples?
Thanks!