From: Paul Lutus <nospam@...>
Date: 2006-12-13T19:50:13+09:00
Subject: Re: Restricted capture in Regexp

benjohn@fysh.org wrote:

/ ...

> thanks for the reply. I know I can do this, but it means that the
> substitution ("\\1\\2\\3") has to be aware of the composition of the
> regular expression.

Yes, that is true for all regular expressions.

> The Regexp is no longer a neat little machine that 
> only grabs things to replace. It's now grabbing the packaging around the
> thing to replace too, so you've got to be aware of this in writing the
> substitution.

Yes, but this cannot be avoided. You have two choices for examined text that
surrounds the area to be modified -- you can capture it while examining it,
and use the captured text in the replacement, or you can use non-capturing
references:

(?=non-captured text)

But the two alternatives work much the same way -- they examine text that is
preserved as part of the overall regular expression. All that changes
is /how/ the text is preserved.

So, to move ahead, please post a specific example of what you need. Post an
example of the original string and the desired replacement.

It is scarcely possible to describe in prose what one wants from a regular
expression. It /is/ possible to take a first step by posting an example of
original text, and replacement text. Maybe we should try that.

-- 
Paul Lutus
http://www.arachnoid.com