Roman numerals? I have never encountered a regex implementation where '\d' matches 'X'. It's certainly not the case for Javascript: http://regexpal.com/?flags=g&regex=\d%2B&input=10%0Ax%0AX%0A...

There's a whole lot of these numeral characters in unicode, for example:

http://www.charbase.com/2169-unicode-roman-numeral-ten

(even more in http://www.charbase.com/block/number-forms)

I'm not sure if Javascript matches these in its \d pattern, however, but I think that most regexp engines default to the ascii [0-9] unless you are using \p{Number}.

There's also the character classes in Unicode:

http://www.fileformat.info/info/unicode/category/index.htm

> /\d/.test("\u2169")

false

Ruby also does not match roman numerals with \d

http://rubular.com/r/bOCmLIfKdZ

\d finds arabic numerals? As in 0-9? Scandalous :)

http://en.wikipedia.org/wiki/Arabic_numerals

Perhaps they mean Eastern Arabic numerals. http://en.wikipedia.org/wiki/Eastern_Arabic_numerals

Indeed - those are in use by millions of people. I wonder if any regexp implementation has started matching all of the other number symbols in Unicode:

http://en.wikipedia.org/wiki/Numerals_in_Unicode

Perl does, by default.

There's a modifier if you want to only match ASCII digits.