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Re: regexp and strings you don't want


From: Kai Großjohann
Subject: Re: regexp and strings you don't want
Date: Wed, 27 Aug 2003 22:26:23 +0200
User-agent: Gnus/5.1003 (Gnus v5.10.3) Emacs/21.3.50 (gnu/linux)

address@hidden (Chaz) writes:

> For example, how can I search for a paragraph beginning with "The"
> that does NOT include the word "top"?

It is possible to build a regexp that does this (disregarding the
paragraph problem at the moment), but it is not pretty.

Some regexp implementations have the feature you're looking for to
make it convenient, but the Emacs implementation doesn't.

Let me rephrase this in terms of lines instead of paragraphs.

The idea is this: search for a line that begins with The and then
does not have top after it, as follows: after The, we allow any
characters that aren't t.  We also allow a t followed by something
that's not o, and also a to that's followed by something that's not
p.  And so on:

"^The\\([^t]*\\($\\|t$\\|t[^o]\\|to$\\|to[^p]\\)\\)*$"

The above regexp is in Lisp syntax, with doubled backslashes.  Note
that I treat the newline that might follow a t, or to, specially.

Do you see the idea?  I hope I haven't made a mistake, but if you
understand the idea, you'll see what to do.
-- 
Two cafe au lait please, but without milk.


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