• Yeah, but “elf” are not digits. Digits are a symbol abstracted from the language itself. Does 5 and V convey different meanings in the context of digits? And yeah, I can see why they would argue about the implementation because inclusivity is important. Especially when designing a language implementation. If you are designing it wrong, it will be very hard to extend it in the future. But for application level implementation, go nuts.

    • You are right, “elf” is a stretch, it does not make sense to parse it as a number. But in some languages, the string “15 240,5” is just how a number is written (yes, that’s a U+2009 THIN SPACE, you can’t stop me from using it as a thousand separator in German). Obviously, despite having a , on their numpads, German programmers still expect computers to parse numbers with decimal dots and interpret commas as list values.

      • Alright, maybe you misunderstood the term digits with numbers. When parsing a digit, you do not attach semantic yet to the building blocks. A \d regex parser does not care that the string “555” is not equivalent to “VVV”. All it cares about is that there is the digit “5” or “V”. In the same vein, regex parser should not try to parse IV as a single symbol.