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Regular expression use


For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for. Not the subject
domain, but the construction of the regular expressions.

I know about computer scientists and parsing, and I know about
the use of relatively simple ones for things like extracting
HTML links from Web pages. But I don't have much feel for the
(probably rare but difficult) uses of more complex ones for
other purposes. I have heard of several such uses, but don't
have an overall idea of what is going on.

Any pointers appreciated, to more-or-less anything.
Regards,
Nick Maclaren.
Aug 24 '07 #1
14 1233
Nick Maclaren <nm**@cus.cam.ac.ukwrote in comp.lang.perl.misc:
>
For reasons that I won't explain, as they are too complicated
and not terribly relevant,
Your reasons are relevant as a motivation for your readers to
answer such a broad question.
I am interested in discovering what
people actually use regular expressions for. Not the subject
domain, but the construction of the regular expressions.
How is the construction of a regex related to what it is used
for? That makes no sense.
I know about computer scientists and parsing,
That's a (broad) subject domain.
and I know about
the use of relatively simple ones for things like extracting
HTML links from Web pages.
That's another subject domain (and a regex for that purpose wouldn't
qualify as "relatively simple").
But I don't have much feel for the
(probably rare but difficult) uses of more complex ones for
other purposes. I have heard of several such uses, but don't
have an overall idea of what is going on.
Your question is so badly defined, it would take considerable effort
just to make sense of it. Given your premise of "Never mind what I
need it for, just gimme the info," I won't even try.

Anno
Aug 24 '07 #2
On 24 Aug 2007 10:58:46 GMT, nm**@cus.cam.ac.uk (Nick Maclaren) wrote:
>
For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for. Not the subject
domain, but the construction of the regular expressions.

I know about computer scientists and parsing, and I know about
the use of relatively simple ones for things like extracting
HTML links from Web pages. But I don't have much feel for the
(probably rare but difficult) uses of more complex ones for
other purposes. I have heard of several such uses, but don't
have an overall idea of what is going on.

Any pointers appreciated, to more-or-less anything.
In the linked project, regular expression are used to parse
communication protocol responses, file contents, and interporocess
communcation (at least).

They may not be pretty elegant solutions, but this is the first
project I made in python (and also with regex)!!

NOTE: I am the author, and I swear the application is free of viruses,
it has been fully developed with a python and a WingWare standar
installation, and it will only deposit some files on your
$python$/Lib/site-packages folder.
Any comments welcome.

NOTE2: Software in spanish, but it should not be pretty difficult to
follow (I hope!)

best regards,

Zara

http://www.albalaing.com/Firmware.aspx?id_firmware=2359

Aug 24 '07 #3
Nick,

In "Mastering Regular Expressions" by Jeffrey E. F. Friedl your
question is answered in the first 6 chapters. Seriously, that's what
it takes. It's a really good book.

Cheers

Bert

On Aug 24, 12:58 pm, n...@cus.cam.ac.uk (Nick Maclaren) wrote:
For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for. Not the subject
domain, but the construction of the regular expressions.

I know about computer scientists and parsing, and I know about
the use of relatively simple ones for things like extracting
HTML links from Web pages. But I don't have much feel for the
(probably rare but difficult) uses of more complex ones for
other purposes. I have heard of several such uses, but don't
have an overall idea of what is going on.

Any pointers appreciated, to more-or-less anything.

Regards,
Nick Maclaren.

Aug 24 '07 #4
In article <fa**********@gemini.csx.cam.ac.uk>,
Nick Maclaren <nm**@cus.cam.ac.ukwrote:
>
For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for. Not the subject
domain, but the construction of the regular expressions.
Your question as phrased makes no sense to me. For that matter, it isn't
even a question. ;-)

Side note: please don't cross-post between c.l.py and c.l.perl.* -- the
group cultures are different and it's too easy to start flamewars.
--
Aahz (aa**@pythoncraft.com) <* http://www.pythoncraft.com/

"If you don't know what your program is supposed to do, you'd better not
start writing it." --Dijkstra
Aug 24 '07 #5

In article <fa**********@mlucom4.urz.uni-halle.de>,
Mirco Wahab <wa********@gmx.netwrites:
|>
|Using complex regular expressions is like tank destruction
|with contact charges glued on them. Only a few people
|will even survive the first "usage", but survivors will
|then eventually be able to destroy almost every tank with
|tremendous speed and precision.

I must remember that! It is nicely put.

|On business software projects, maintainability is a key
|prerequisite - after using complex regular expressions
|on business critical parts you are bound to involve
|very very expensive maintenance programmers ... :)

Yes :-) Even regular expression experts have major problems
ensuring that complicated ones match everything that they need
to and nothing that they don't. The same thing applies to
uses of the C preprocessor and many uses of Perl ....

|What exactly did you "hear" of several "uses"? Which
|application? Academia, Business, ...?

Mainly academic research, but that still covers many fields.
However, I am not and never have been a 'pure' academic, and
am as interested in other uses as in academic research.
Regards,
Nick Maclaren.
Aug 24 '07 #6
On 2007-08-24, Nick Maclaren <nm**@cus.cam.ac.ukwrote:
people actually use regular expressions for. Not the subject
domain, but the construction of the regular expressions.
This is easy.
I use RE for checking whether some input matches a certain pattern, and
optionally, to extract some special part from the text.

Albert
Aug 24 '07 #7
On Aug 24, 6:58 am, n...@cus.cam.ac.uk (Nick Maclaren) wrote:
I am interested in discovering what
people actually use regular expressions for.
Hmm - let's see. I tend to use regular expressions when I am writing
code that needs to search through output to find certain patterns. I
also use them to convert text in one format into another format. I
also frequently use them to validate input - if I need input to be all
alphabetics, or a properly formatted floating point number, etc.

Aug 24 '07 #8
Nick Maclaren wrote:
For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for.
Finding credit card numbers in files...among other things:

http://filebox.vt.edu/users/rtilley/public/find_ccns/
Aug 24 '07 #9
On 24 Aug 2007 10:58:46 GMT, Nick Maclaren <nm**@cus.cam.ac.ukwrote:
>
For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for.
http://xkcd.com/208/

--
Cheers,
Simon B.
si***@brunningonline.net
http://www.brunningonline.net/simon/blog/
GTalk: simon.brunning | MSN: small_values | Yahoo: smallvalues
Aug 24 '07 #10
Simon Brunning wrote:
On 24 Aug 2007 10:58:46 GMT, Nick Maclaren <nm**@cus.cam.ac.ukwrote:
>For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for.

http://xkcd.com/208/

That was the one that got me hooked on xkcd. I remember laughing so hard
at that. A friend and I still quote that one (and others).

/W
Aug 24 '07 #11
I work in print (book) production and i regularly use regular
expressions to parse .eps (encapsulated postscript) files for
incorrect specifications (8-bit vs. ASCII, etc), bad fonts and the
like. Just to ensure that what's been submitted to me will actually
end up on the page.

Aug 24 '07 #12
Nick Maclaren a écrit :
For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for.
Usually, to obfuscate code. Sometimes for good reasons....

Hu ? Ok, me get out ---->[]
Aug 25 '07 #13
Nick Maclaren wrote:
For reasons that I won't explain, as they are too complicated
and not terribly relevant, I am interested in discovering what
people actually use regular expressions for. Not the subject
domain, but the construction of the regular expressions.

I know about computer scientists and parsing, and I know about
the use of relatively simple ones for things like extracting
HTML links from Web pages. But I don't have much feel for the
(probably rare but difficult) uses of more complex ones for
other purposes. I have heard of several such uses, but don't
have an overall idea of what is going on.

Any pointers appreciated, to more-or-less anything.
I just don't get what you're after!
Lots of data is available in text form, so sifting though it requires
regular expressions.
A better question would be: what do you use Perl for, as I'd say most
Perl programs utilize REs at some point or the other.
But IIRC we've had that thread already.

--
Mails please to josef dot moellers
and I'm on gmx dot de.
Aug 25 '07 #14
John W. Krahn <kr****@telus.netwrote in comp.lang.perl.misc:
Nick Maclaren wrote:
In article <fa**********@mlucom4.urz.uni-halle.de>,
Mirco Wahab <wa********@gmx.netwrites:
|>
|Using complex regular expressions is like tank destruction
|with contact charges glued on them. Only a few people
|will even survive the first "usage", but survivors will
|then eventually be able to destroy almost every tank with
|tremendous speed and precision.

I must remember that! It is nicely put.

I couldn't understand it. (An old Centurion trooper.)
Me neither. The word "nicely" isn't the first thing it brings to
mind.

Anno
Aug 25 '07 #15

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