From: Daniel DeLorme <dan-ml@...42.com>
Date: 2006-09-21T09:01:12+09:00
Subject: Re: Unicode and Character Classes -- a bug?

Richard Wiseman wrote:
> puts "Pattern includes \"[x\xa3]\":"
> text.scan(/^[x\xa3]?[A-Z]$/).each {|s| puts s }

That is very weird indeed. It's normal that your example doesn't work, because 
\xa3 is NOT valid utf8. But I would've expected it to work if you used the 
correct utf8 sequence for "炭" ("\xc3\xba"), except it doesn't!

$KCODE='u'
=> "u"
text = "\xc3\xbaA\nB\n\xc3\xbaC\nxD\nE"
=> "炭A\nB\n炭C\nxD\nE"
text.scan(/^[x炭]?[A-Z]$/)
=> ["炭A", "B", "炭C", "xD", "E"]
text.scan(/^[x\xc3\xba]?[A-Z]$/)
=> ["B", "xD", "E"]

WTF? Can anyone explain this?