[30744] in Perl-Users-Digest
Perl-Users Digest, Issue: 1989 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Nov 18 06:09:50 2008
Date: Tue, 18 Nov 2008 03:09:15 -0800 (PST)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Tue, 18 Nov 2008 Volume: 11 Number: 1989
Today's topics:
Re: atoi/atof sln@netherlands.com
Re: File operation and Concatenation <gokul.bits@gmail.com>
Re: How would I do the following? <tadmc@seesig.invalid>
Re: How would I do the following? <jl_post@hotmail.com>
new CPAN modules on Tue Nov 18 2008 (Randal Schwartz)
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
Re: Regular expressions: how to skip characters from a <rvtol+news@isolution.nl>
Re: Regular expressions: how to skip characters from a <bart.lateur@pandora.be>
Re: Regular expressions: how to skip characters from a sln@netherlands.com
Re: Regular expressions: how to skip characters from a <bugbear@trim_papermule.co.uk_trim>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Mon, 17 Nov 2008 23:27:35 GMT
From: sln@netherlands.com
Subject: Re: atoi/atof
Message-Id: <mlq3i4llgv1jb1amqnjg7f8fejn15h8n2i@4ax.com>
On Mon, 17 Nov 2008 17:14:28 +0100, "Peter J. Holzer" <hjp-usenet2@hjp.at> wrote:
>On 2008-11-16 21:06, sln@netherlands.com <sln@netherlands.com> wrote:
>> On Sat, 15 Nov 2008 19:37:00 +0100, "Peter J. Holzer" <hjp-usenet2@hjp.at> wrote:
>>>On 2008-11-14 04:41, Jürgen Exner <jurgenex@hotmail.com> wrote:
>>>> debjyoti@gmail.com wrote:
>>>>>I was messing around with a perl script and realized converting
>>>>>strings to integers/floats is iffy on perl (compared to C).
>>>>
>>>> Really?
>>>
>>>Yes, really. The Perl routines for converting between strings and
>>>numbers are buggy.
>>>
>>>> I haven't noticed.
>>>
>>>I guess most people haven't, or the bugs would be fixed already. These
>>>bugs have been there for a very long time, but they show up only if you
>>>get close to the 15 digits/53 bits of FP precision.
>>>
>>>I'm almost sure the OP's code is even buggier, though. String/number
>>>conversions aren't trivial.
>>>
>>> hp
>>
>> ">>>strings to integers/floats is iffy on perl (compared to C). "
>>
>> Aren't trivial? So ANSI C++ hasn't got it right yet?
>
>"ANSI C++" is a specification. It only defines what needs to be done,
>not how to do it. You would have to look at specific implementations.
>Anyway, C++ is irrelevant here, as perl is written in C, not C++.
>
>> Perl had to bypass.
>
>ANSI C has a strtod function for string -> floating point conversion.
>I'm not sure if perl uses it (it's been some time since I looked at the
>code, sorry), but it probably could and should use it, as I would expect
>it to be correct on all major platforms. If perl doesn't use it, it is
>probably for historical reasons. Easy to fix.
>
>Unfortunately, there is no reverse function in C: sprintf generates a
>fixed number of digits after the decimal point, which is either too
>little or too much. So that's something perl has to do itself.
>
>> Its the other way around, number to string isin't trivial.
>
>Conversion to and from integers is trivial (typical exercise for first
>semester students). Conversion to and from FP numbers isn't trivial in
>either direction. The situation is only asymmetric because C already has
>a nice function for conversion from strings to numbers (which shields
>the C programmer from all the hairy stuff), but not for the
>reverse.
>
> hp
Well, as you said ANSI is just a specification. But its specific enough.
I'm going out on a limb here and listing a specific implementation for
Microsofts C libraries, ie: all Window's platforms:
ANSI Windows
String->Number Number->String
----------------- ----------------
atoi/atol/strol _itoa/_ltoa
atof/strtod _fcvt/_ecvt
I think these are C. Seems unusual Perl is built on
platforms without using thier ANSI and/or OS specific functions.
A large majority of these conversions are done in assembly
(not just compiled into assembly) and fully optimized.
I can see possibly not wanting to deal with the individual
platrom exception processing though.
It just never occurred to me these standard calls are not made,
and home-grown routines are used instead. Its got to be slower.
Apparently there is no ASNI equivalent Number->String. Most
platforms have them though.
String->Number is a one way street to load parameters.
Number->String is a view.
There should be no circular input/output relationship between them.
It's been my experience with C/C++ that precision is the culprit
and cause of calculation "drift" and/or unexpected results.
Nothing too real is measurable/manufacturable below 1/10 of a micron.
Thats not alot of decimal places. As soon as a term above that is introduced
into a calculation, terms below are insignificant.
Therefore IMO, PI = 3.14
sln
------------------------------
Date: Tue, 18 Nov 2008 01:44:40 -0800 (PST)
From: Gokul <gokul.bits@gmail.com>
Subject: Re: File operation and Concatenation
Message-Id: <48e9d3be-8787-40fa-b567-870ed13871e5@s9g2000prg.googlegroups.com>
I just gave FIVE instances to illustrate my purpose only.
FIVE is insignificant.
File A and File B might have a lot of strings in them.10s or 100s.
But the string catenation plays an important role.
However your idea was thought-Provoking.
Thanks
------------------------------
Date: Mon, 17 Nov 2008 18:08:34 -0600
From: Tad J McClellan <tadmc@seesig.invalid>
Subject: Re: How would I do the following?
Message-Id: <slrngi41s2.u44.tadmc@tadmc30.sbcglobal.net>
jl_post@hotmail.com <jl_post@hotmail.com> wrote:
> However, this only works if "expression" returns an array. If,
> instead, it returns a list, "scalar(expression)" would return the last
> element.
No, if it returns a list, then you must know which list
function "expression" represents before you can know what
will be returned in scalar context.
(and also note that it does NOT "return a list". It is not possible
to return a list into scalar context...
)
Here are 3 "expressions" that do not return the last element, for example:
--------------------
#!/usr/bin/perl
use warnings;
use strict;
my $return = scalar grep /o/, qw/one two three/;
print "$return\n";
$return = scalar reverse qw/one two three/;
print "$return\n";
$return = scalar map $_, qw/one two three/;
print "$return\n";
--------------------
Note also that the "scalar" keyword has no effect in the above code.
The assignment operator is already providing scalar context, so
an explicit scalar() is not needed.
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.noitatibaher\100cmdat/"
------------------------------
Date: Mon, 17 Nov 2008 17:15:18 -0800 (PST)
From: "jl_post@hotmail.com" <jl_post@hotmail.com>
Subject: Re: How would I do the following?
Message-Id: <0238c70f-a7b8-4048-a88a-ba2e913c0cbe@o4g2000pra.googlegroups.com>
> jl_p...@hotmail.com <jl_p...@hotmail.com> wrote:
> >
> > However, this only works if "expression" returns an array. If,
> > instead, it returns a list, "scalar(expression)" would return the last
> > element.
On Nov 17, 5:08 pm, Tad J McClellan <ta...@seesig.invalid> replied:
>
> No, if it returns a list, then you must know which list
> function "expression" represents before you can know what
> will be returned in scalar context.
Oh, that's true. Some functions will return the number of elements
when used in scalar context even if they normally return a list in
list context. In that case, nothing special needs to be done other
than assigning "expression" to a scalar (or evaluating it in a scalar
context).
In the past, though, I have been burned by shoddy documentation
that said an array would be returned, when in fact it returned a
list. The code:
my $numElements = function();
should have worked, but instead it put the last element into
$numElements, which isn't what I wanted. As a result, I often use
instead:
my $numElements = () = function();
especially when the documentation makes no mention of context. That
way, if in some future revision of the code, a maintainer changed code
like:
my @array = (1, -1);
return @array;
to:
return (1, -1);
and not updated the documentation to reflect that change, my own code
would be safe.
> (and also note that it does NOT "return a list". It is not possible
> to return a list into scalar context...)
Sure, agreed. I didn't mean to imply that it could. What I meant
to imply is that if you call a function that normally returns a list,
you will get a scalar if you call it in scalar context. And unlike
with arrays, this scalar will not necessarily be the number of
elements. (It can be, but unless the documentation explicitly says
so, I wouldn't depend on it.)
What I DID neglect to mention were functions that behave
differently based on context (such as those that use the wantarray()
function).
-- Jean-Luc
------------------------------
Date: Tue, 18 Nov 2008 05:42:23 GMT
From: merlyn@stonehenge.com (Randal Schwartz)
Subject: new CPAN modules on Tue Nov 18 2008
Message-Id: <KAIL6n.D3@zorch.sf-bay.org>
The following modules have recently been added to or updated in the
Comprehensive Perl Archive Network (CPAN). You can install them using the
instructions in the 'perlmodinstall' page included with your Perl
distribution.
Apache-SWIT-0.4
http://search.cpan.org/~bosu/Apache-SWIT-0.4/
mod_perl based application server with integrated testing.
----
Apache-SWIT-Security-0.05
http://search.cpan.org/~bosu/Apache-SWIT-Security-0.05/
security subsystem for Apache::SWIT
----
App-Benchmark-Accessors-0.04
http://search.cpan.org/~marcel/App-Benchmark-Accessors-0.04/
benchmark accessor generators
----
App-ZofCMS-0.0109
http://search.cpan.org/~zoffix/App-ZofCMS-0.0109/
web framework and templating system for small-medium sites.
----
App-ZofCMS-0.0110
http://search.cpan.org/~zoffix/App-ZofCMS-0.0110/
web framework and templating system for small-medium sites.
----
App-ZofCMS-0.0111
http://search.cpan.org/~zoffix/App-ZofCMS-0.0111/
web framework and templating system for small-medium sites.
----
App-ZofCMS-Plugin-QuickNote-0.0106
http://search.cpan.org/~zoffix/App-ZofCMS-Plugin-QuickNote-0.0106/
drop-in "quicknote" form to email messages from your site
----
Astro-SIMBAD-Client-0.016
http://search.cpan.org/~wyant/Astro-SIMBAD-Client-0.016/
Fetch astronomical data from SIMBAD 4.
----
Badger-0.03_01
http://search.cpan.org/~abw/Badger-0.03_01/
Perl Application Programming Toolkit
----
CLI-Dispatch-0.02
http://search.cpan.org/~ishigaki/CLI-Dispatch-0.02/
simple CLI dispatcher
----
CPAN-WWW-Testers-0.37
http://search.cpan.org/~barbie/CPAN-WWW-Testers-0.37/
Present CPAN Testers data
----
Catalyst-Action-Serialize-SimpleExcel-0.012
http://search.cpan.org/~rkitover/Catalyst-Action-Serialize-SimpleExcel-0.012/
Serialize tables to Excel files
----
CatalystX-CRUD-Model-RDBO-0.16
http://search.cpan.org/~karman/CatalystX-CRUD-Model-RDBO-0.16/
Rose::DB::Object CRUD
----
CatalystX-CRUD-YUI-0.008
http://search.cpan.org/~karman/CatalystX-CRUD-YUI-0.008/
YUI for your CatalystX::CRUD view
----
Class-Accessor-Grouped-0.08002
http://search.cpan.org/~claco/Class-Accessor-Grouped-0.08002/
Lets you build groups of accessors
----
Class-Wheel-0.01
http://search.cpan.org/~plcgi/Class-Wheel-0.01/
simple class wheel
----
Config-Any-0.16
http://search.cpan.org/~bricas/Config-Any-0.16/
Load configuration from different file formats, transparently
----
Config-Any-Merge-0.05
http://search.cpan.org/~mdom/Config-Any-Merge-0.05/
Overrinding of configuration variables based on file order
----
DBD-ODBC-1.17_2
http://search.cpan.org/~mjevans/DBD-ODBC-1.17_2/
ODBC Driver for DBI
----
DBIx-Admin-CreateTable-2.01
http://search.cpan.org/~rsavage/DBIx-Admin-CreateTable-2.01/
A module for creating and dropping tables and sequences
----
DBIx-Class-OptimisticLocking-0.01
http://search.cpan.org/~bphillips/DBIx-Class-OptimisticLocking-0.01/
Optimistic locking support for DBIx::Class
----
DBIx-Class-RDBOHelpers-0.08
http://search.cpan.org/~karman/DBIx-Class-RDBOHelpers-0.08/
DBIC compat with Rose::DBx::Object::MoreHelpers
----
DBIx-Perlish-0.48
http://search.cpan.org/~gruber/DBIx-Perlish-0.48/
a perlish interface to SQL databases
----
DTS-0.07
http://search.cpan.org/~arfreitas/DTS-0.07/
Perl classes to access Microsoft SQL Server 2000 DTS Packages
----
Data-Util-0.21
http://search.cpan.org/~gfuji/Data-Util-0.21/
A selection of utilities for data and data types
----
Digest-Skein-0.03
http://search.cpan.org/~radek/Digest-Skein-0.03/
Perl interface to the Skein digest algorithm
----
Encode-JavaScript-Cyrillic-0.01
http://search.cpan.org/~plcgi/Encode-JavaScript-Cyrillic-0.01/
Javascript bug fix for cyrillic((bug : %u0410 -%u044f))
----
File-SafeDO-0.12
http://search.cpan.org/~miker/File-SafeDO-0.12/
safer do file for perl
----
GD-Thumbnail-1.30
http://search.cpan.org/~burak/GD-Thumbnail-1.30/
Thumbnail maker for GD
----
GnuPG-Interface-0.40_02
http://search.cpan.org/~jesse/GnuPG-Interface-0.40_02/
Perl interface to GnuPG
----
HTML-Parser-3.58
http://search.cpan.org/~gaas/HTML-Parser-3.58/
HTML parser class
----
HTML-Tested-0.46
http://search.cpan.org/~bosu/HTML-Tested-0.46/
Provides HTML widgets with the built-in means of testing.
----
IO-Lambda-0.41
http://search.cpan.org/~karasik/IO-Lambda-0.41/
non-blocking I/O in lambda style
----
IO-MultiPipe-0.0.0
http://search.cpan.org/~vvelox/IO-MultiPipe-0.0.0/
Allows for error checking on a command involving multiple pipes.
----
IO-Socket-SSL-1.18
http://search.cpan.org/~sullr/IO-Socket-SSL-1.18/
Nearly transparent SSL encapsulation for IO::Socket::INET.
----
LWP-Simple-WithCache-0.01
http://search.cpan.org/~leeym/LWP-Simple-WithCache-0.01/
LWP::Simple with cache
----
Log-Syslog-UDP-0.11
http://search.cpan.org/~athomason/Log-Syslog-UDP-0.11/
Perl extension for very quickly sending syslog messages over UDP.
----
MIME-Lite-3.023
http://search.cpan.org/~rjbs/MIME-Lite-3.023/
low-calorie MIME generator
----
Mail-SPF-Iterator-0.02
http://search.cpan.org/~sullr/Mail-SPF-Iterator-0.02/
iterative SPF lookup
----
Net-DNSBL-Monitor-0.10
http://search.cpan.org/~miker/Net-DNSBL-Monitor-0.10/
Monitor DNSBL response
----
Net-DNSBL-MultiDaemon-0.26
http://search.cpan.org/~miker/Net-DNSBL-MultiDaemon-0.26/
multi DNSBL prioritization
----
Net-DNSBL-Statistics-0.12
http://search.cpan.org/~miker/Net-DNSBL-Statistics-0.12/
gather DNSBL Statistics
----
Net-IMAP-Server-1.06
http://search.cpan.org/~alexmv/Net-IMAP-Server-1.06/
A single-threaded multiplexing IMAP server implementation, using Net::Server::Coro.
----
Net-Jifty-0.08
http://search.cpan.org/~sartak/Net-Jifty-0.08/
interface to online Jifty applications
----
Net-OpenSSH-0.01
http://search.cpan.org/~salva/Net-OpenSSH-0.01/
Perl SSH client package implemented on top of OpenSSH
----
Net-OpenSSH-0.02
http://search.cpan.org/~salva/Net-OpenSSH-0.02/
Perl SSH client package implemented on top of OpenSSH
----
Padre-0.17
http://search.cpan.org/~szabgab/Padre-0.17/
Perl Application Development and Refactoring Environment
----
Parse-MediaWikiDump-0.55
http://search.cpan.org/~triddle/Parse-MediaWikiDump-0.55/
Tools to process MediaWiki dump files
----
PostScript-MailLabels-2.30
http://search.cpan.org/~ajackson/PostScript-MailLabels-2.30/
Modules for creating PostScript(tm) files of mailing address labels.
----
Rose-DBx-Object-I18N-0.04
http://search.cpan.org/~vti/Rose-DBx-Object-I18N-0.04/
set of modules to deal with multilingual database
----
Rose-HTMLx-Form-Related-0.12
http://search.cpan.org/~karman/Rose-HTMLx-Form-Related-0.12/
RHTMLO forms, living together
----
Rubyish-Attribute-0.05
http://search.cpan.org/~shelling/Rubyish-Attribute-0.05/
ruby-like accessor builder: attr_accessor, attr_writer and attr_reader.
----
Sledge-Cache-Memcached-Fast-0.02
http://search.cpan.org/~tokuhirom/Sledge-Cache-Memcached-Fast-0.02/
Cache::Memcached::Fast bindings for Sledge::Cache
----
Sledge-Cache-Memcached-Fast-0.03
http://search.cpan.org/~tokuhirom/Sledge-Cache-Memcached-Fast-0.03/
Cache::Memcached::Fast bindings for Sledge::Cache
----
Sledge-Cache-Memcached-Fast-0.04
http://search.cpan.org/~tokuhirom/Sledge-Cache-Memcached-Fast-0.04/
Cache::Memcached::Fast bindings for Sledge::Cache
----
Storable-AMF-0.17
http://search.cpan.org/~grian/Storable-AMF-0.17/
Perl extension for serialize/deserialize AMF0/AMF3 data
----
WWW-Netflix-API-0.07
http://search.cpan.org/~davidrw/WWW-Netflix-API-0.07/
Interface for Netflix's API
----
WWW-Scraper-ISBN-Amazon_Driver-0.14
http://search.cpan.org/~barbie/WWW-Scraper-ISBN-Amazon_Driver-0.14/
----
WWW-Scraper-ISBN-Yahoo_Driver-0.08
http://search.cpan.org/~barbie/WWW-Scraper-ISBN-Yahoo_Driver-0.08/
Search driver for Yahoo Books online catalog.
----
WWW-Search-PharmGKB-1.02
http://search.cpan.org/~arun/WWW-Search-PharmGKB-1.02/
Search and retrieve information from the PharmGKB database
----
WWW-Search-PharmGKB-1.03
http://search.cpan.org/~arun/WWW-Search-PharmGKB-1.03/
Search and retrieve information from the PharmGKB database
----
WWW-Wikipedia-TemplateFiller-0.06
http://search.cpan.org/~diberri/WWW-Wikipedia-TemplateFiller-0.06/
Fill Wikipedia templates with your eyes closed
----
Win32-FTDI-FTD2XX-1.04
http://search.cpan.org/~skmacphe/Win32-FTDI-FTD2XX-1.04/
PERL5 interface to FTDI's D2XX Direct USB Drivers
----
Win32API-File-0.1101
http://search.cpan.org/~chorny/Win32API-File-0.1101/
Low-level access to Win32 system API calls for files/dirs.
----
Xacobeo-0.03_01
http://search.cpan.org/~potyl/Xacobeo-0.03_01/
XPath (XML Path Language) visualizer.
----
perlindex-1.605
http://search.cpan.org/~ulpfr/perlindex-1.605/
index and query perl manual pages
If you're an author of one of these modules, please submit a detailed
announcement to comp.lang.perl.announce, and we'll pass it along.
This message was generated by a Perl program described in my Linux
Magazine column, which can be found on-line (along with more than
200 other freely available past column articles) at
http://www.stonehenge.com/merlyn/LinuxMag/col82.html
print "Just another Perl hacker," # the original
--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<merlyn@stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
Smalltalk/Perl/Unix consulting, Technical writing, Comedy, etc. etc.
See http://methodsandmessages.vox.com/ for Smalltalk and Seaside discussion
------------------------------
Date: Tue, 18 Nov 2008 08:10:56 GMT
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.8 $)
Message-Id: <kMuUk.6768$x%.5539@nlpi070.nbdc.sbc.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.8 $)
This newsgroup, commonly called clpmisc, is a technical newsgroup
intended to be used for discussion of Perl related issues (except job
postings), whether it be comments or questions.
As you would expect, clpmisc discussions are usually very technical in
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The article at:
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describes how to get answers from technical people in general.
This article describes things that you should, and should not, do to
increase your chances of getting an answer to your Perl question. It is
available in POD, HTML and plain text formats at:
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For more information about netiquette in general, see the "Netiquette
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http://andrew2.andrew.cmu.edu/rfc/rfc1855.html
A note to newsgroup "regulars":
Do not use these guidelines as a "license to flame" or other
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A note about technical terms used here:
In this document, we use words like "must" and "should" as
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Do *NOT* send email to the maintainer of these guidelines. It will be
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writes down the consensus of the group.
Before posting to comp.lang.perl.misc
Must
This section describes things that you *must* do before posting to
clpmisc, in order to maximize your chances of getting meaningful replies
to your inquiry and to avoid getting flamed for being lazy and trying to
have others do your work.
The perl distribution includes documentation that is copied to your hard
drive when you install perl. Also installed is a program for looking
things up in that (and other) documentation named 'perldoc'.
You should either find out where the docs got installed on your system,
or use perldoc to find them for you. Type "perldoc perldoc" to learn how
to use perldoc itself. Type "perldoc perl" to start reading Perl's
standard documentation.
Check the Perl Frequently Asked Questions (FAQ)
Checking the FAQ before posting is required in Big 8 newsgroups in
general, there is nothing clpmisc-specific about this requirement.
You are expected to do this in nearly all newsgroups.
You can use the "-q" switch with perldoc to do a word search of the
questions in the Perl FAQs.
Check the other standard Perl docs (*.pod)
The perl distribution comes with much more documentation than is
available for most other newsgroups, so in clpmisc you should also
see if you can find an answer in the other (non-FAQ) standard docs
before posting.
It is *not* required, or even expected, that you actually *read* all of
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before posting.
Try doing a word-search in the standard docs for some words/phrases
taken from your problem statement or from your very carefully worded
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Really Really Should
This section describes things that you *really should* do before posting
to clpmisc.
Lurk for a while before posting
This is very important and expected in all newsgroups. Lurking means
to monitor a newsgroup for a period to become familiar with local
customs. Each newsgroup has specific customs and rituals. Knowing
these before you participate will help avoid embarrassing social
situations. Consider yourself to be a foreigner at first!
Search a Usenet archive
There are tens of thousands of Perl programmers. It is very likely
that your question has already been asked (and answered). See if you
can find where it has already been answered.
One such searchable archive is:
http://groups.google.com/advanced_group_search
If You Like
This section describes things that you *can* do before posting to
clpmisc.
Check Other Resources
You may want to check in books or on web sites to see if you can
find the answer to your question.
But you need to consider the source of such information: there are a
lot of very poor Perl books and web sites, and several good ones
too, of course.
Posting to comp.lang.perl.misc
There can be 200 messages in clpmisc in a single day. Nobody is going to
read every article. They must decide somehow which articles they are
going to read, and which they will skip.
Your post is in competition with 199 other posts. You need to "win"
before a person who can help you will even read your question.
These sections describe how you can help keep your article from being
one of the "skipped" ones.
Is there a better place to ask your question?
Question should be about Perl, not about the application area
It can be difficult to separate out where your problem really is,
but you should make a conscious effort to post to the most
applicable newsgroup. That is, after all, where you are the most
likely to find the people who know how to answer your question.
Being able to "partition" a problem is an essential skill for
effectively troubleshooting programming problems. If you don't get
that right, you end up looking for answers in the wrong places.
It should be understood that you may not know that the root of your
problem is not Perl-related (the two most frequent ones are CGI and
Operating System related), so off-topic postings will happen from
time to time. Be gracious when someone helps you find a better place
to ask your question by pointing you to a more applicable newsgroup.
How to participate (post) in the clpmisc community
Carefully choose the contents of your Subject header
You have 40 precious characters of Subject to win out and be one of
the posts that gets read. Don't waste them. Take care while
composing them, they are the key that opens the door to getting an
answer.
Spend them indicating what aspect of Perl others will find if they
should decide to read your article.
Do not spend them indicating "experience level" (guru, newbie...).
Do not spend them pleading (please read, urgent, help!...).
Do not spend them on non-Subjects (Perl question, one-word
Subject...)
For more information on choosing a Subject see "Choosing Good
Subject Lines":
http://www.cpan.org/authors/id/D/DM/DMR/subjects.post
Part of the beauty of newsgroup dynamics, is that you can contribute
to the community with your very first post! If your choice of
Subject leads a fellow Perler to find the thread you are starting,
then even asking a question helps us all.
Use an effective followup style
When composing a followup, quote only enough text to establish the
context for the comments that you will add. Always indicate who
wrote the quoted material. Never quote an entire article. Never
quote a .signature (unless that is what you are commenting on).
Intersperse your comments *following* each section of quoted text to
which they relate. Unappreciated followup styles are referred to as
"top-posting", "Jeopardy" (because the answer comes before the
question), or "TOFU" (Text Over, Fullquote Under).
Reversing the chronology of the dialog makes it much harder to
understand (some folks won't even read it if written in that style).
For more information on quoting style, see:
http://web.presby.edu/~nnqadmin/nnq/nquote.html
Speak Perl rather than English, when possible
Perl is much more precise than natural language. Saying it in Perl
instead will avoid misunderstanding your question or problem.
Do not say: I have variable with "foo\tbar" in it.
Instead say: I have $var = "foo\tbar", or I have $var = 'foo\tbar',
or I have $var = <DATA> (and show the data line).
Ask perl to help you
You can ask perl itself to help you find common programming mistakes
by doing two things: enable warnings (perldoc warnings) and enable
"strict"ures (perldoc strict).
You should not bother the hundreds/thousands of readers of the
newsgroup without first seeing if a machine can help you find your
problem. It is demeaning to be asked to do the work of a machine. It
will annoy the readers of your article.
You can look up any of the messages that perl might issue to find
out what the message means and how to resolve the potential mistake
(perldoc perldiag). If you would like perl to look them up for you,
you can put "use diagnostics;" near the top of your program.
Do not re-type Perl code
Use copy/paste or your editor's "import" function rather than
attempting to type in your code. If you make a typo you will get
followups about your typos instead of about the question you are
trying to get answered.
Provide enough information
If you do the things in this item, you will have an Extremely Good
chance of getting people to try and help you with your problem!
These features are a really big bonus toward your question winning
out over all of the other posts that you are competing with.
First make a short (less than 20-30 lines) and *complete* program
that illustrates the problem you are having. People should be able
to run your program by copy/pasting the code from your article. (You
will find that doing this step very often reveals your problem
directly. Leading to an answer much more quickly and reliably than
posting to Usenet.)
Describe *precisely* the input to your program. Also provide example
input data for your program. If you need to show file input, use the
__DATA__ token (perldata.pod) to provide the file contents inside of
your Perl program.
Show the output (including the verbatim text of any messages) of
your program.
Describe how you want the output to be different from what you are
getting.
If you have no idea at all of how to code up your situation, be sure
to at least describe the 2 things that you *do* know: input and
desired output.
Do not provide too much information
Do not just post your entire program for debugging. Most especially
do not post someone *else's* entire program.
Do not post binaries, HTML, or MIME
clpmisc is a text only newsgroup. If you have images or binaries
that explain your question, put them in a publically accessible
place (like a Web server) and provide a pointer to that location. If
you include code, cut and paste it directly in the message body.
Don't attach anything to the message. Don't post vcards or HTML.
Many people (and even some Usenet servers) will automatically filter
out such messages. Many people will not be able to easily read your
post. Plain text is something everyone can read.
Social faux pas to avoid
The first two below are symptoms of lots of FAQ asking here in clpmisc.
It happens so often that folks will assume that it is happening yet
again. If you have looked but not found, or found but didn't understand
the docs, say so in your article.
Asking a Frequently Asked Question
It should be understood that you may have missed the applicable FAQ
when you checked, which is not a big deal. But if the Frequently
Asked Question is worded similar to your question, folks will assume
that you did not look at all. Don't become indignant at pointers to
the FAQ, particularly if it solves your problem.
Asking a question easily answered by a cursory doc search
If folks think you have not even tried the obvious step of reading
the docs applicable to your problem, they are likely to become
annoyed.
If you are flamed for not checking when you *did* check, then just
shrug it off (and take the answer that you got).
Asking for emailed answers
Emailed answers benefit one person. Posted answers benefit the
entire community. If folks can take the time to answer your
question, then you can take the time to go get the answer in the
same place where you asked the question.
It is OK to ask for a *copy* of the answer to be emailed, but many
will ignore such requests anyway. If you munge your address, you
should never expect (or ask) to get email in response to a Usenet
post.
Ask the question here, get the answer here (maybe).
Beware of saying "doesn't work"
This is a "red flag" phrase. If you find yourself writing that,
pause and see if you can't describe what is not working without
saying "doesn't work". That is, describe how it is not what you
want.
Sending a "stealth" Cc copy
A "stealth Cc" is when you both email and post a reply without
indicating *in the body* that you are doing so.
Be extra cautious when you get upset
Count to ten before composing a followup when you are upset
This is recommended in all Usenet newsgroups. Here in clpmisc, most
flaming sub-threads are not about any feature of Perl at all! They
are most often for what was seen as a breach of netiquette. If you
have lurked for a bit, then you will know what is expected and won't
make such posts in the first place.
But if you get upset, wait a while before writing your followup. I
recommend waiting at least 30 minutes.
Count to ten after composing and before posting when you are upset
After you have written your followup, wait *another* 30 minutes
before committing yourself by posting it. You cannot take it back
once it has been said.
AUTHOR
Tad McClellan and many others on the comp.lang.perl.misc newsgroup.
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.noitatibaher\100cmdat/"
------------------------------
Date: Tue, 18 Nov 2008 00:08:09 +0100
From: "Dr.Ruud" <rvtol+news@isolution.nl>
Subject: Re: Regular expressions: how to skip characters from a capture
Message-Id: <gft12u.1tc.1@news.isolution.nl>
Ikke schreef:
> I'd like to have a
> regular expression which always returns filename, whether the original
> line states filename or "filename", but not "filename or filename" .
/("?)([^" ]*)\1/
--
Affijn, Ruud
"Gewoon is een tijger."
------------------------------
Date: Tue, 18 Nov 2008 05:44:16 +0100
From: Bart Lateur <bart.lateur@pandora.be>
Subject: Re: Regular expressions: how to skip characters from a capture
Message-Id: <jlh4i4l2our529ijvnmp0mn7s3n208uq27@4ax.com>
Ikke wrote:
>I've created something like: ((filename)|quote(filename)quote) which
>matches the text as I would like, but it doesn't capture the text as
>expected.
>
>If there are no quotes, the text is returned as group 1. If there are
>quotes, group 2 returns the filename with the quotes. I'd like the quotes
>to be removed from this group.
Much simpler is to just use the whole capture and strip the quotes from
this afterwards.
Either that, or you have to loop through the captures till you find one
that isn't undefined (or empty?), except for the outer one (maybe make
it noncapturing).
BTW Perl has the $+ special variable for this purpose. See perlvar:
$+ The text matched by the last bracket of the last successful
search pattern. This is useful if you don't know which one
of a set of alternative patterns matched. For example:
/Version: (.*)|Revision: (.*)/ && ($rev = $+);
(Mnemonic: be positive and forward looking.) This variable
is read-only and dynamically scoped to the current BLOCK.
It might not be so trivial in Delphi.
--
Bart.
------------------------------
Date: Tue, 18 Nov 2008 04:50:02 GMT
From: sln@netherlands.com
Subject: Re: Regular expressions: how to skip characters from a capture
Message-Id: <5sh4i4pn3h9h6hhofd52i05ps10bti7idc@4ax.com>
On Mon, 17 Nov 2008 14:45:39 -0800, Jürgen Exner <jurgenex@hotmail.com> wrote:
>Ikke <ikke@hier.be> wrote:
>>I am trying to build a regex, which needs to capture data from a .csv
>>file in a very specific format.
>>
>>The first part should be a filename - either enclosed in quotes, or not.
>>This is the part that is giving me problems.
>
>Why aren't you using a parser for parsing CSV? There are several module
>on CPAN.
>
>>I've created something like: ((filename)|quote(filename)quote) which
>>matches the text as I would like, but it doesn't capture the text as
>>expected.
>
>So, let me paraphrase: sometime the data elements in your CSV are
>enclosed in quotes. And you want them without quotes, no matter if they
>are stored with or without quotes. Right?
>
>>Does anybody know a solution for this problem?
>
>REs are not powerful enough to match balanced items, please see "perldoc
>-q balanced" for more details.
>Just use a CSV parser module, it will take care of the de-quoting
>automatically.
>
>jue
I can only see this post in my reader (Agent), my usenet provider (easynews)
is acting flakey lately. Not too sure what the issue is with the OP.
I didn't see any Perl regexp there so it might be some other flavor.
This regexp will match alot, thus it needs help with a conditional.
Good Luck!
use strict;
use warnings;
while (<DATA>)
{
chomp;
next if (!length());
print "\nline = $_\n";
# Try this if you can't do the while/global search below
# ------------------------------------------------------
# if (/(,?)("?)(filename)("?)/ && $2 eq $4)
while (/(,?)("?)(filename)("?)/g)
{
next if ( $2 ne $4);
print "------------------\n";
print "\tFound: <$1>\n";
print "\tFound: <$2>\n";
print "\tFound: <$3>\n"; # <- where it is
print "\tFound: <$4>\n";
}
}
__DATA__
asdfasdfasd asdasdf
"filename"
filename
filename,filename
,"filename",
"filename,filename"
filename,filename"
"filename,filename
"filename
filename"
filename",filename,"filename"
------------------------------
Date: Tue, 18 Nov 2008 09:26:30 +0000
From: bugbear <bugbear@trim_papermule.co.uk_trim>
Subject: Re: Regular expressions: how to skip characters from a capture
Message-Id: <0aKdncsNsoLaF7_UnZ2dnUVZ8h6dnZ2d@posted.plusnet>
Ikke wrote:
> Hi everybody,
>
> First of all, if this is not the right group to ask, I apologize. I could
> not find a specific regex group, so I decided to turn to those who know
> Perl.
>
> I am trying to build a regex, which needs to capture data from a .csv
> file in a very specific format.
>
> The first part should be a filename - either enclosed in quotes, or not.
> This is the part that is giving me problems.
>
> I've created something like: ((filename)|quote(filename)quote) which
> matches the text as I would like, but it doesn't capture the text as
> expected.
>
> If there are no quotes, the text is returned as group 1. If there are
> quotes, group 2 returns the filename with the quotes. I'd like the quotes
> to be removed from this group. I assumed that, if the first part of the
> expression matches, the double braces would indicate that group 2 would
> return the name as well, but this is not the case. Apparently ((regex))
> equals (regex).
>
> Does anybody know a solution for this problem?
I would use one of the many CSV parsers to remove part of the problem,
leaving a hopefully simpler problem.
BugBear
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
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Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
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End of Perl-Users Digest V11 Issue 1989
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