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From: Eric Bednarz <bednarz@fahr-zur-hoelle.org>
Newsgroups: comp.lang.javascript
Subject: Re: ScreenName validation
Organization: Eric Conspiracy Secret Labs
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Date: Sat, 12 Jan 2013 00:54:21 +0100
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Stefan Weiss <krewecherl@gmail.com> writes:

> On 2013-01-11 23:23, Eric Bednarz wrote:
>> Stefan Weiss <krewecherl@gmail.com> writes:
>> 
>>> Could you give an example of when the literal ] character doesn't have
>>> to be escaped in a character class?
>> 
>> I'm not sure what you are asking.
>
> I may have misunderstood what you wrote. I interpreted it as: "the
> literal ] has to be escaped because empty character classes are legal in
> ECMAScript".

Don't you agree with that in your final statement:

|> Actually, now I can't think of a language other than ECMAScript that
|> supports empty classes, so "many implementations" was probably wrong.

?

> So, I think it would be better to say that ] always has to be escaped,
> except in this one specific edge case (which cannot occur in ECMAScript).

As far as I'm concerned, it's no more of an edge case than not escaping
`^' if it's not at the start of a character class, and not escaping `-'
if it's at the beginning or end of a character class, or right after the
negator. It just looks more obscure, but if you're not in the two
problems camp and think about REs in general, I would consider the
`pattern' itself common knowledge.