From: Florian Gilcher <flo@...>
Date: 2008-11-19T21:01:10+09:00
Subject: Re: RegExp problem

>
>
> Hi Florian,
>
> I don't get what you mean by "too heavily rely", I mean, you are
> always relying on the behaviour of the regexp library when it comes to
> everything, so if you know how the dot, the * and the ? work in Ruby
> why is your regexp better than the proposed one?
>
> Anyway I have realized I had a mistake in my regexp (I had the ?
> outside of the group, and not next to the *). So fixing that:
>
> irb(main):034:0> string="rzerze@foo@rezrzgrtez"
> => "rzerze@foo@rezrzgrtez"
> irb(main):035:0> re = Regexp.new("([#{delimiter}])(.*?)\\1")
> => /([abcde])(.*?)\1/
> irb(main):036:0> string.match(re)[2]
> => "rz"
>
> Now works as I intended. With your version:
>
> irb(main):037:0> re = /([#{delimiter}])([^#{delimiter}]*)\1/
> => /([abcde])([^abcde]*)\1/
> irb(main):038:0> string.match(re)[2]
> => "rz"
>
> works too. So I would like to know why would be one preferred over  
> the other.
>
> Jesus.
>

Hi Jesus,

Because you could get problems when you have things like this:

"foo@fooo@bar@batz@foo"

you rely on the the behaviour of the dot. Meaning: yours matches

fooo@bar@batz

Thus, it ignores all inner delimiters.
In any case, mine matches:

[["fooo"],["batz"]] #String#scan output

Depending on how the dot is treated (greediness etc.), yours
could also have other interpretations (like mine) while mine is  
clearer in
that respect.

In a simple case with only 2 delimiters, it doesn't matter.

Actually, mine wasn't correct either, i also forgot the brackets...

/#{delimiter}([^#{delimiter}])*#{delimiter}/

For more readibility, here is the version with delimiter = @:

/@([^@]*)@/

Regards,
Florian Gilcher