From: "David A. Black" <dblack@...>
Date: 2008-03-17T12:17:23+09:00
Subject: Re: returning text between two markers without markers inclu

Hi --

On Mon, 17 Mar 2008, Xavier Noria wrote:

> On Mar 16, 2008, at 21:23 , Adam Akhtar wrote:
>
>> I haven't seen the /mx term before, is that reponsible for not including
>> the markers themselves?
>
> Those are two regexp modifiers stacked together:
>
> * With /m the dot matches newlines. I couldn't assume the text to extract 
> doesn't contain newlines so I added it just in case.
>
> * With /x literal whitespace in the regexp are ignored. Since the regexp uses 
> so many backslashes that gives some air for readability.

I know I'm in the minority, but I'll just mention that I find most
regexes that make use of /x very hard to read. The reason is that I've
trained my brain how to read a pattern, so if I encounter this:

   / string (.*) another ? string /x

it's a considerable effort to "not see" the spaces. I think it's
better to stick to the basic pattern language, which after all is the
only set of rules that we all learn and all share.

I would recommend saving /x for cases where you want to break a regex
out into multiple lines and include comments:

   re = /
          \(              # opening paren
          \d{3}           # area code
          \)              # closing paren

etc. (Not a great example of an obscure pattern that's made more clear
by /x but you get the idea.)


David

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