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Posted by Alan Little on 05/23/06 03:52
Carved in mystic runes upon the very living rock, the last words of Andy
Jeffries of comp.lang.php make plain:
> On Mon, 22 May 2006 13:47:39 -0500, Alan Little wrote:
>>> However, you do make the good point that you don't *need* to escape
>>> the -, I just do it for readability so there's no mistaking that I
>>> meant a literal dash and not part of a range that I forgot to
>>> complete.
>>
>> OK. I don't believe it's standard, however.
>
> On p79 of Mastering Regular Expressions by Jeffrey E F Friedl (ISBN
> 1-56592-257-3) it says:
>
> "In limited-metacharacter-class implementations, other metacharacter
> (including in most tools, even backslashes) are not recognized. So,
> for example, you can't use \- or \] to insert a hyphen or a closing
> bracket in to the class." This precedes a list of characters that are
> available in these limited implementations which are specifically: a
> leading caret, the closing bracket and a dash as a range operator.
>
> I'm sure that book details the "standard" for regular expressions in
> most people's eyes and that book (as quoted above) uses \- as the
> syntax to insert a literal hyphen with a metacharacter class ([...]).
>
> So it would seem that while [^0-9-] works in PHP/Perl, it's actually
> not standard and I am correct to use [^0-9\-] in order to ensure
> maximum compatibility with future version which may implement the
> standard more strictly.
That's a good reference, but I don't follow you. The part you quoted from
the book says you *can't* use \- to insert a hyphen in the class.
--
Alan Little
Phorm PHP Form Processor
http://www.phorm.com/
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