Re: Stack-based behaviour of Regexes

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From: Kevin Burton (KevinBurton_at_discussions.microsoft.com)
Date: 08/31/04 

Date: Mon, 30 Aug 2004 21:07:15 -0700

I had thought of that and that will be one possible work-around. I would like
to avoid bringing in the DOM for two reasons:

1) I am concerned about the overhead. These are relatively short strings
(most less than 1K) and the DOM seems overkill and costly in terms of cycles
and memory for just these strings. Regex can be compiled and it just seems
faster although I have not done benchmarks on it. I know there are some
constructs in the DOM that are VERY costly. Simple things like counting
elements were killing a web application that we had.
2) I want to understand how to handle nested constructs using regular
expressions. It seems to work OK for single character open and close entities
like parenthesis but it should be extendable to entities greater than one
character.

I just need the start and end of a possibly nested structure. So for example

<A> This is some text
<OPTIONAL>This is some <OPTIONAL>optional text</OPTIONAL></OPTIONAL>
<B>This is some B text
<OPTIONAL>This is some more optional text </OPTIONAL>
</A>

For the first <OPTIONAL> tag I would like the index into the string where
this begins and where the corresponding </OPTIONAL> tag ends (so the index
would essentially point to the beginning of <B>). For the next <OPTIONAL> tag
I would want the beginning and ending of that tag and content, and so forth.
If regular expressions can be used to do nested parenthesis then can't a
regular expression be put together to handle nested tags?

Kevin

"Mike D Sutton" wrote:

> > Have you been able to expand this to more than one characters? I have nexted
> > XML tags that I would like to do the same thing with. Here is my best guess
> > (it does not work). Basically the tag is <OPTIONAL> and the end tag is
> > </OPTIONAL>. These can be nested with other tags in between. The regex I have
> > shown below allows for attributes.
>
> Why not just use the MSXML DOM and XPath queries to find your data within the XML file? Are you just looking for <OPTIONAL> tags or
> something specific within them?
> Hope this helps,
>
> Mike
>
>
> - Microsoft Visual Basic MVP -
> E-Mail: EDais@mvps.org
> WWW: http://www.mvps.org/EDais/
>
>
>

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