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Re: ScreenName validation

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On 2013-01-11 21:22, Eric Bednarz wrote:
> Eric Bednarz <bednarz@fahr-zur-hoelle.org> writes:
> 
>> The only character that *must* to be escaped in a character class is the
>> escape character itself.
> 
> While this is true in most modern regular expression implementations, I
> just realized that it is actually false in ECMAScript, which
> inexplicably features empty character classes, so a closing square
> bracket literal actually has to be escaped.

Could you give an example of when the literal ] character doesn't have
to be escaped in a character class?

The empty character class is supported in many (but not all) PCRE-like
regex implementations. It matches any character that belongs to the set
of no characters - in other words, it will never match. I'm not sure
where that would be useful. The inverse case, [^], matches any
character. It actually has a use, because it also matches newlines
(which are not matched by the "." special character).

In addition to "\", "]", and "-", some languages also require the regex
delimiter to be escaped in regex literals.

  /[/]/.test("/")            // true in ECMAScript
  "/" =~ /[/]/                # syntax error in Perl
  /[/]/.match("/")            # syntax error in Ruby
  preg_match("/[/]/", "/")   // syntax error in PHP

ECMAScript is the odd one out here. For that reason, and because it can
mess up syntax highlighting, I'd also escape a slash in a character class.

> Except for JScript < 10. Them damn implementations of. :-)

JScript behaving differently from the rest? Shocking.


- stefan

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Thread

ScreenName validation "Mel Smith" <med_cutout_syntel@aol.com> - 2013-01-08 10:44 -0700
  Re: ScreenName validation Scott Sauyet <scott.sauyet@gmail.com> - 2013-01-08 11:02 -0800
    Re: ScreenName validation "Mel Smith" <med_cutout_syntel@aol.com> - 2013-01-08 13:05 -0700
    Re: ScreenName validation Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-01-11 01:28 +0100
      Re: ScreenName validation Jeff North <jnorthau@yahoo.com.au> - 2013-01-11 12:23 +1100
        Re: ScreenName validation Stefan Weiss <krewecherl@gmail.com> - 2013-01-11 03:38 +0100
        Re: ScreenName validation Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-01-11 20:35 +0100
          Re: ScreenName validation Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-01-11 21:22 +0100
            Re: ScreenName validation Stefan Weiss <krewecherl@gmail.com> - 2013-01-11 22:09 +0100
              Re: ScreenName validation Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-01-11 23:23 +0100
                Re: ScreenName validation Stefan Weiss <krewecherl@gmail.com> - 2013-01-12 00:26 +0100
                Re: ScreenName validation Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-01-12 00:54 +0100
              Re: ScreenName validation Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-01-12 00:22 +0100
          Re: ScreenName validation Scott Sauyet <scott.sauyet@gmail.com> - 2013-01-11 13:29 -0800
            Re: ScreenName validation Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-01-12 02:31 +0100

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