Posted by Andy Jeffries on 05/22/06 22:13

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.

Cheers,



Andy

--
Andy Jeffries MBCS CITP ZCE | gPHPEdit Lead Developer
http://www.gphpedit.org | PHP editor for Gnome 2
http://www.andyjeffries.co.uk | Personal site and photos

[Back to original message]