[32061] in Perl-Users-Digest
Perl-Users Digest, Issue: 3325 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Fri Mar 18 06:09:29 2011
Date: Fri, 18 Mar 2011 03:09:11 -0700 (PDT)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Fri, 18 Mar 2011 Volume: 11 Number: 3325
Today's topics:
Re: "getting" a website <Uno@example.invalid>
Re: "getting" a website <Uno@example.invalid>
Re: convenient module to take statistics for hashed str <ela@yantai.org>
Re: convenient module to take statistics for hashed str <nospam.gravitalsun@hotmail.com.nospam>
Re: DBD::mysql used to take octets into the utf8 texts <rvtol+usenet@xs4all.nl>
Re: FAQ 2.2 How can I get a binary version of perl? <rvtol+usenet@xs4all.nl>
Is there any point in using a reference to an object? <news@lawshouse.org>
Re: Is there any point in using a reference to an objec <bugbear@trim_papermule.co.uk_trim>
Re: Is there any point in using a reference to an objec <news@lawshouse.org>
Re: Is there any point in using a reference to an objec <tadmc@seesig.invalid>
Re: Is there any point in using a reference to an objec <blgl@stacken.kth.se>
Re: List assignment to array affects scalar results <derykus@gmail.com>
Re: List assignment to array affects scalar results <xhoster@gmail.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
Re: reading .ini file without using a module <alfonso.baldaserra@gmail.com>
Re: recursive Pythagorian triples <nospam.gravitalsun@hotmail.com.nospam>
Re: recursive Pythagorian triples <xhoster@gmail.com>
Re: recursive Pythagorian triples <cartercc@gmail.com>
Re: recursive Pythagorian triples <bugbear@trim_papermule.co.uk_trim>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Fri, 18 Mar 2011 02:45:30 -0600
From: Uno <Uno@example.invalid>
Subject: Re: "getting" a website
Message-Id: <8ugkdbFqdnU1@mid.individual.net>
On 03/10/2011 06:35 AM, Tad McClellan wrote:
[re-ordered, for thematic reasons}
> Uno<Uno@example.invalid> wrote:
> $_ is a variable.
>
> It cannot "return" anything.
>
> It does have a value though:
>
> why is the value of $_ more than I wanted.
>
>
> For us to answer that, we would need to know what you wanted!
>
> What did you want?
What I want is a reasonable discussion of perl. My notion of
"reasonable" might be another's notion of "highly idiomatic and usually OT."
I suspect that a default variable is something that one just has to get
used to, like quantum mechanics.
> Most excellent! You have found the right spot.
>
>
>> q43) How do I match on zip as well?
>
>
> By adding alternation and grouping:
>
> (pdf|zip) # last part
>
> or, since you are already using the m//x modifier:
>
> ( # last part (will be available in $1)
> pdf | zip # either one of these
> )
>
> or, if you don't need to capture:
>
> (?: # last part
> pdf | zip # either one of these
> )
>
>
>
$ perl gurl9.pl
http://www.germanresistance.com/documents/Intro_to_Bonhoeffer.pdf
success is 200
http://www.germanresistance.com/documents/Chronology_of_the_life_of_Dietrich_Bonhoeffer.pdf
success is 200
http://www.germanresistance.com/documents/Bonhoeffer_on_Abortion.pdf
success is 200
http://www.germanresistance.com/documents/Luther_Bonhoeffer_and_Revolution.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_and_the_Russian_Religious_Renaissance.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_the_resistance_and_the_two_kingdoms.pdf
success is 200
http://www.germanresistance.com/documents/Pius_XII_and_the_Jews.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_and_the_German_Resistance_'95.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_and_Liberalism.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_and_Canossa.pdf
success is 200
http://www.germanresistance.com/documents/Invidious_Comparisons.pdf
success is 200
http://www.germanresistance.com/documents/Agent_of_Grace.pdf
success is 200
http://www.germanresistance.com/documents/The_stereotyping_of_Dietrich_Bonhoeffer.pdf
success is 200
http://www.germanresistance.com/documents/From_Dietrich_Bonhoeffer’s_Wedding_Sermon.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_and_the_Theology_of_the_Cross.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_on_Authority.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_and_the_Formula_of_Concord.pdf
success is 200
http://www.germanresistance.com/documents/The_German_Resistance_60_years.pdf
success is 200
http://www.germanresistance.com/documents/Dietrich_Bonhoeffer_and_Karl_Barth.pdf
success is 200
http://www.germanresistance.com/documents/Luther_and_Bonhoeffer_misunderstood.pdf
success is 200
http://www.germanresistance.com/documents/The_German_Resistance_and_Dietrich_Bonhoeffer_'07.pdf
success is 200
http://www.germanresistance.com/documents/GermanResistanceV2.zip
success is 200
$ cat gurl9.pl
#!/usr/bin/perl -w
# gurl - get content from an url
use LWP::Simple;
require HTML::TokeParser;
my $file = "bonhoeffer2";
my $URL = 'http://germanresistance.com/index-of-papers/';
my $p = HTML::TokeParser->new(bonhoeffer2);
while (my $token = $p->get_tag("a")) {
my $url = $token->[1]{href} || "-";
if ($url =~
"http://www.germanresistance.com/documents.*(pdf|zip)" ) {
print "$url\n";
my $success = getstore( $url, "/pdfs/$url" );
print "success is $success\n";
}
}
So why am I told that 200 is my success when I have none?
--
Uno
------------------------------
Date: Fri, 18 Mar 2011 02:57:12 -0600
From: Uno <Uno@example.invalid>
Subject: Re: "getting" a website
Message-Id: <8ugl39Fv7fU1@mid.individual.net>
On 03/10/2011 04:24 AM, Jürgen Exner wrote:
> perldoc perlretut
$ perldoc perlretut
You need to install the perl-doc package to use this program.
$
Apparently, perl documentation doesn't survive a re-install, necessarily.
--
Uno
------------------------------
Date: Thu, 17 Mar 2011 17:22:36 -0700
From: "ela" <ela@yantai.org>
Subject: Re: convenient module to take statistics for hashed structures?
Message-Id: <ilsg9t$iiq$1@ijustice.itsc.cuhk.edu.hk>
"George Mpouras" <nospam.gravitalsun@hotmail.com.nospam> wrote in message
news:ilqvvv$nui$1@news.ntua.gr...
>
> # This one meet your requirements
> # It can handle even more data than the previous versions
I'm sorry to report that when I feed the threshold to be smaller than 50,
e.g. 10, the result will be
H=2,6;
This result, although passes the threshold, in fact I only needs the largest
one, i.e. 3 (50% abundant), which is not reported and then why does
statement
foreach my $RANK (keys %{$data{$_[0]}->[$i]})
{
return [$col[$i], $data{$_[0]}->[$i]->{$RANK}] if $RANK >= $_[1]
}
can return two values? when one of the "$RANK" fulfill the requirement, I
think the subroutine will return....
------------------------------
Date: Thu, 17 Mar 2011 13:14:05 +0200
From: "George Mpouras" <nospam.gravitalsun@hotmail.com.nospam>
Subject: Re: convenient module to take statistics for hashed structures?
Message-Id: <ilsqcs$2s6o$1@news.ntua.gr>
"ela" <ela@yantai.org> wrote in message
news:ilsg9t$iiq$1@ijustice.itsc.cuhk.edu.hk...
>
> "George Mpouras" <nospam.gravitalsun@hotmail.com.nospam> wrote in message
> news:ilqvvv$nui$1@news.ntua.gr...
>>
>> # This one meet your requirements
>> # It can handle even more data than the previous versions
>
> I'm sorry to report that when I feed the threshold to be smaller than 50,
> e.g. 10, the result will be
>
> H=2,6;
>
> This result, although passes the threshold, in fact I only needs the
> largest one, i.e. 3 (50% abundant), which is not reported and then why
> does statement
>
> foreach my $RANK (keys %{$data{$_[0]}->[$i]})
> {
> return [$col[$i], $data{$_[0]}->[$i]->{$RANK}] if $RANK >= $_[1]
> }
>
> can return two values? when one of the "$RANK" fulfill the requirement, I
> think the subroutine will return....
>
# You only have to change one line for this behavior
#
# foreach my $RANK (sort {$b <=> $a} keys %{$data{$_[0]}->[$i]})
#
# All together again is
my @col;
my %data;
ReadData();
$_ = query('01',10);
print "Field=$_->[0],Value=@{$_->[1]}\n";
sub ReadData
{
while (<DATA>) { chomp;
my @a = split /\s*\|\s*/, $_, -1;
if (-1 == $#col){push @col, @a[1..$#a] ;next}
unless (1+$#col==$#a) {warn "Skip line number $. \"$_\" because it have
".(1+$#a)." fields, while it should have ".(1+$#col)."\n";next}
$data{$a[0]}->[0]++;
for(my $i=1;$i<=$#a;$i++){$data{$a[0]}->[1]->[$i-1]->[0]->{$a[$i]}++}}
foreach my $id (keys %data)
{
foreach my $f ( @{$data{$id}->[1]} )
{
foreach my $v ( keys %{$f->[0]} )
{
push @{ $f->[1]->{int 100*( $f->[0]->{$v}/$data{$id}->[0])} }, $v
}
# remove unnecessary structures
$f = $f->[1]
}
# remove unnecessary structures
$data{$id} = $data{$id}->[1]
}
#use Data::Dumper; print Dumper(\%data);exit;
}
sub query
{
for(my $i=$#{$data{$_[0]}}; $i>=0; $i--)
{
foreach my $RANK (sort {$b <=> $a} keys %{$data{$_[0]}->[$i]})
{
return [$col[$i], $data{$_[0]}->[$i]->{$RANK}] if $RANK >= $_[1]
}
}
['',[]]
}
__DATA__
ID|B|C|D|E|F|G|H
01|3|7|9|3|4|2|3
01|3|7|9|3|4|2|2
01|3|7|9|5|8|6|6
01|3|7|9|3|4|2|3
02|4|7|9|3|4|2|1
02|4|7|9|3|4|2|2
02|4|7|9|3|4|2|3
02|4|7|9|3|4|2|3
------------------------------
Date: Thu, 17 Mar 2011 13:28:53 +0100
From: "Dr.Ruud" <rvtol+usenet@xs4all.nl>
Subject: Re: DBD::mysql used to take octets into the utf8 texts but no more in mariadb
Message-Id: <4d81fe85$0$41117$e4fe514c@news.xs4all.nl>
On 2011-03-15 00:54, Peter Vereshagin wrote:
> Output coming 3rd is my solution and the 4th is yours ( and not only yours ).
I didn't give you any solution, just a pointer to 'SET NAMES'.
> whom of software authors should I ask about that strange behavior?
There is nothing strange about that behavior, it all works as documented.
You need to check (and compare) the character set settings on all levels
(connection, database, table, column), to find out where the differences
come from.
Good reads are:
http://dev.mysql.com/doc/refman/5.1/en/charset.html
http://code.openark.org/blog/mysql/mysqls-character-sets-and-collations-demystified
Another confused person:
http://www.bluebox.net/news/2009/07/mysql_encoding
--
Ruud
------------------------------
Date: Thu, 17 Mar 2011 13:40:02 +0100
From: "Dr.Ruud" <rvtol+usenet@xs4all.nl>
Subject: Re: FAQ 2.2 How can I get a binary version of perl?
Message-Id: <4d820122$0$41113$e4fe514c@news.xs4all.nl>
On 2011-03-17 04:02, brian d foy wrote:
> In article<4d7e8ce5$0$81474$e4fe514c@news.xs4all.nl>, Dr.Ruud
> <rvtol+usenet@xs4all.nl> wrote:
>> Another nice one:
>>
>> Citrus Perl
>> http://www.cava.co.uk/
>
> Has anyone used this? Is it good enough to be in the FAQ?
I saw that Johan Vromans uses it for Eekboek.
Then it must be good enough for everybody.
:)
http://wiki.eekboek.nl/mediawiki/index.php?title=Platform:MacOSX
http://www.cava.co.uk/citrusperl/osx32.html
Citrus Perl includes the minimum additional modules needed to support:
Wx
DBD::SQLite
DBD::Pg
DBD::mysql
To me it looks like a Strawberry with graphics, and databases.
--
Ruud
------------------------------
Date: Thu, 17 Mar 2011 09:23:17 +0000
From: Henry Law <news@lawshouse.org>
Subject: Is there any point in using a reference to an object?
Message-Id: <uaCdnf23rfqbThzQnZ2dnUVZ8vGdnZ2d@giganews.com>
My application has need to create a hierarchy of objects, all of the
same type: $obj_a "owns" (or contains) $obj_b and $obj_c; $obj_c in turn
owns d, e and f, and so on. It's necessary to be able to go forward
among siblings (b -> c, or d -> e -> f) and also to be able to go "down"
to the first child (a to b, c to d).
My immediate idea was to include in the object's own hash references to
the next object, whether "down" or "forward", thus
$self->{first_child} = \$first_child_object;
$self->{next_sibling} = \$next_sibling_object;
but it occurs to me that the object variable is itself just a reference,
so that
$self->{first_child} = $first_child_object;
would have the same effect. Most importantly I don't want to *copy*
$first_child_object, just provide a way of getting to it, and its
methods, from $self. (You can see that I'm somewhat of a novice at OO
Perl).
Is my thinking correct? Or is there a different and better way of
doing what I want?
--
Henry Law Manchester, England
------------------------------
Date: Thu, 17 Mar 2011 10:28:30 +0000
From: bugbear <bugbear@trim_papermule.co.uk_trim>
Subject: Re: Is there any point in using a reference to an object?
Message-Id: <K82dnQUxBOLSfxzQnZ2dnUVZ8jCdnZ2d@brightview.co.uk>
Henry Law wrote:
> My application has need to create a hierarchy of objects, all of the
> same type: $obj_a "owns" (or contains) $obj_b and $obj_c; $obj_c in turn
> owns d, e and f, and so on. It's necessary to be able to go forward
> among siblings (b -> c, or d -> e -> f) and also to be able to go "down"
> to the first child (a to b, c to d).
>
> My immediate idea was to include in the object's own hash references to
> the next object, whether "down" or "forward", thus
>
>
> $self->{next_sibling} = \$next_sibling_object;
>
> but it occurs to me that the object variable is itself just a reference,
> so that
>
> $self->{first_child} = $first_child_object;
>
> would have the same effect. Most importantly I don't want to *copy*
> $first_child_object, just provide a way of getting to it, and its
> methods, from $self. (You can see that I'm somewhat of a novice at OO
> Perl).
>
> Is my thinking correct? Or is there a different and better way of doing
> what I want?
Assuming that you're "near" to a solution, I will point out
that your scalars (the variable with a preceding $) are already
references to hashes, equivalent to a pointer in C.
I suspect you've come from a Java background, where "objects"
are actually references to objects. Since this is ALWAYS
the case in Java, most Java programmers just call them "objects".
Back to perl - since your scalars are already references (to hashes)
you can treat them as you would in Java, or as you would pointers in 'C'.
In particular, unless you trying to do something Macintosh like
("Handles", allowing memory motion), you don't need to do
$self->{first_child} = \$first_child_object;
As you worked out:
$self->{first_child} = $first_child_object;
is fine.
BugBear
------------------------------
Date: Thu, 17 Mar 2011 10:41:00 +0000
From: Henry Law <news@lawshouse.org>
Subject: Re: Is there any point in using a reference to an object?
Message-Id: <8d6dnTYRp5OjeBzQnZ2dnUVZ7tCdnZ2d@giganews.com>
On 17/03/11 10:28, bugbear wrote:
> In particular, unless you trying to do something Macintosh like
> ("Handles", allowing memory motion), you don't need to do
>
> $self->{first_child} = \$first_child_object;
>
> As you worked out:
>
> $self->{first_child} = $first_child_object;
Excellent; thank you for confirming what I'd worked out. I'm conscious
that "you can't just make stuff up and hope that it will work" ...
(Is that (c) Tad McClellan?)
--
Henry Law Manchester, England
------------------------------
Date: Thu, 17 Mar 2011 11:30:11 -0500
From: Tad McClellan <tadmc@seesig.invalid>
Subject: Re: Is there any point in using a reference to an object?
Message-Id: <slrnio4df5.3hc.tadmc@tadbox.sbcglobal.net>
Henry Law <news@lawshouse.org> wrote:
[snip]
> Excellent; thank you for confirming what I'd worked out. I'm conscious
> that "you can't just make stuff up and hope that it will work" ...
>
> (Is that (c) Tad McClellan?)
Much as I would like to, I cannot lay claim to that one.
It is due to MJD:
BECAUSE YOU CAN'T JUST MAKE SHIT UP AND EXPECT THE COMPUTER TO
MAGICALLY KNOW WHAT YOU MEAN, RETARDO!
http://groups.google.com/groups/search?as_umsgid=6n69o5%247m6%241%40monet.op.net
--
Tad McClellan
email: perl -le "print scalar reverse qq/moc.liamg\100cm.j.dat/"
The above message is a Usenet post.
I don't recall having given anyone permission to use it on a Web site.
------------------------------
Date: Thu, 17 Mar 2011 19:33:38 +0100
From: Bo Lindbergh <blgl@stacken.kth.se>
Subject: Re: Is there any point in using a reference to an object?
Message-Id: <iltk60$pcf$1@speranza.aioe.org>
In article <slrnio4df5.3hc.tadmc@tadbox.sbcglobal.net>,
Tad McClellan <tadmc@seesig.invalid> wrote:
> It is due to MJD:
>
> BECAUSE YOU CAN'T JUST MAKE SHIT UP AND EXPECT THE COMPUTER TO
> MAGICALLY KNOW WHAT YOU MEAN, RETARDO!
The problem with this is that Perl has so much dwimmery in it
that you often _can_ make shit up successfully.
/Bo Lindbergh
------------------------------
Date: Wed, 16 Mar 2011 22:00:26 -0700 (PDT)
From: "C.DeRykus" <derykus@gmail.com>
Subject: Re: List assignment to array affects scalar results
Message-Id: <be0c1bd2-c1a2-4233-8839-e560f864eef3@11g2000prf.googlegroups.com>
On Mar 16, 3:39=A0pm, Mark <goo...@markginsburg.com> wrote:
> Why does the introduction of the assignment to @b affect the value of
> $cnt?
>
> use strict;
> use warnings;
>
> my $cnt;
> my($x,$y,$z);
> my(@ary) =3D qw(a b c d e);
>
> $cnt =3D ( ($x,$y,$z) =3D @ary );
> print "cnt=3D$cnt\n"; # produces 5
>
> my @b;
> $cnt =3D ( @b =3D ($x,$y,$z) =3D @ary );
> print "cnt=3D$cnt\n"; # produces 3
See: perldoc perldata and its explanations
of lists and list vs. scalar context
Specifically, from that doc:
List assignment in scalar context returns the
number of elements produced by the expression
on the right side of the assignment:
$x =3D($foo,$bar) =3D (3,2,1));# set $x to 3, not 2
...
Similarly, in your first case, that evaluates to 5.
The eventual array assignment to @b in the second
case is also evaluated in scalar contest. The first
three elements in @ary are assigned to ($x,$x,$z)
and the additional elements in @ary are discarded.
@b is then assigned ($x,$y,$z) and then is evaluated
in scalar context to yield 3.
--
Charles DeRykus
------------------------------
Date: Thu, 17 Mar 2011 17:21:37 -0700
From: Xho Jingleheimerschmidt <xhoster@gmail.com>
Subject: Re: List assignment to array affects scalar results
Message-Id: <4d82a427$0$32202$ed362ca5@nr5-q3a.newsreader.com>
Mark wrote:
> Why does the introduction of the assignment to @b affect the value of
> $cnt?
It is not the array that does it, it is the extra assignment.
> use strict;
> use warnings;
>
> my $cnt;
> my($x,$y,$z);
> my(@ary) = qw(a b c d e);
>
>
> $cnt = ( ($x,$y,$z) = @ary );
The list assignment is evaluated in a scalar context.
> print "cnt=$cnt\n"; # produces 5
>
> my @b;
> $cnt = ( @b = ($x,$y,$z) = @ary );
The initial list assignment is evaluated in a *list* context, not a
scalar context. The magic only applies to list assignment in a scalar
context.
You get the same thing using a non-array:
$cnt = ( ($x1,$x2,$x3) = ($x,$y,$z) = @ary );
------------------------------
Date: Fri, 18 Mar 2011 02:15:04 -0500
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
Message-Id: <F82dnXNuj8vlmx7QnZ2dnUVZ5uOdnZ2d@giganews.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
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
nature and there are conventions for conduct in technical newsgroups
going somewhat beyond those in non-technical newsgroups.
The article at:
http://www.catb.org/~esr/faqs/smart-questions.html
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:
http://www.rehabitation.com/clpmisc.shtml
For more information about netiquette in general, see the "Netiquette
Guidelines" at:
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
meanness. It is possible that a poster is unaware of things
discussed here. Give them the benefit of the doubt, and just
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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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We're not bossing you around; we're making the point without
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Do *NOT* send email to the maintainer of these guidelines. It will be
discarded unread. The guidelines belong to the newsgroup so all
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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
Perl's standard docs, only that you spend a few minutes searching them
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
"Subject:" header.
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_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.liamg\100cm.j.dat/"
The above message is a Usenet post.
I don't recall having given anyone permission to use it on a Web site.
------------------------------
Date: Wed, 16 Mar 2011 23:46:06 -0700 (PDT)
From: alfonsobaldaserra <alfonso.baldaserra@gmail.com>
Subject: Re: reading .ini file without using a module
Message-Id: <2e416462-aa61-4a33-9018-4d58061b3ba8@u8g2000yqh.googlegroups.com>
> try to create the my.ini with the same data and give a shot !
it was a very serious mistake. i am very sorry and thank you very
much for correcting me.
------------------------------
Date: Thu, 17 Mar 2011 09:11:02 +0200
From: "George Mpouras" <nospam.gravitalsun@hotmail.com.nospam>
Subject: Re: recursive Pythagorian triples
Message-Id: <ilsc4r$1i41$1@news.ntua.gr>
unfortunately ... and can not be saved
------------------------------
Date: Wed, 16 Mar 2011 18:02:25 -0700
From: Xho Jingleheimerschmidt <xhoster@gmail.com>
Subject: Re: recursive Pythagorian triples
Message-Id: <4d829e72$0$32196$ed362ca5@nr5-q3a.newsreader.com>
ccc31807 wrote:
> On Mar 15, 8:12 pm, sreservoir <sreserv...@gmail.com> wrote:
>>> pythag(N) ->
>>> [{A,B,C} ||
>>> A<- seq(1,N),
>>> B<- seq(1,N),
>>> C<- seq(1,N),
>>> A + B + C =< N,
>>> (A * A) + (B * B) =:= C * C].
>> that's not recursive. that's a list comprehension.
>
> Yes, it's a list comprehension. My question was, can you write a
> Pythagorean triple function in Perl using recursion?
The above non-recursive example is what you gave to explain why you
wanted a recursive version in Perl. If we are not to assume that you
are just babbling incoherently, then the most reasonable assumption is
that you for some reason thought the above was recursive. Otherwise
using it as an example is just bizarre.
Xho
------------------------------
Date: Thu, 17 Mar 2011 19:44:50 -0700 (PDT)
From: ccc31807 <cartercc@gmail.com>
Subject: Re: recursive Pythagorian triples
Message-Id: <227d0147-7672-48ed-a367-bc539ff954f7@f30g2000yqa.googlegroups.com>
On Mar 16, 8:02=A0pm, Xho Jingleheimerschmidt <xhos...@gmail.com> wrote:
> The above non-recursive example is what you gave to explain why you
> wanted a recursive version in Perl. =A0If we are not to assume that you
> are just babbling incoherently, then the most reasonable assumption is
> that you for some reason thought the above was recursive. =A0Otherwise
> using it as an example is just bizarre.
You missed the point. I didn't mention the Erlang script to begin with
because it wasn't relevant to the question. I only mentioned it in the
context of providing an explanation of the original post. Perl doesn't
have list comprehensions, as far as I know, so you are correct in that
asking for a Perl script for finding Pythagoriean triples would indeed
be bizarre. But that wasn't the point.
The point was -- Can you find Pythagorean triples in Perl using
recursion? If you want a generalization, how do you solve a problem
that calls for triple recursion. PJH provided one solution that I
didn't like, but the next day I spend almost the entire day trying to
better it, and I failed. I'm not convinced that it can't be done in a
simpler way, but I don't think I can do it.
To make a larger point, Paul Graham has pointed out that different
languages are different, plugging Lisp. MJD showed how to write Perl
using Lisp-like constructs. Someone, I don't remember who, commented
that Perl can do everything Lisp can do except for Lisp macros.
Several years ago, Time Bray authored a famous blog attempted to use
Erlang to construct a database application, and concluded that Erlang
wasn't suited for the job, yet CouchDB uses Erlang.
And please don't point out that Erlang is derived from Prolog, not
Lisp. I know that. I also know that Lisp has iterative constructs, but
Erlang doesn't. The tie to Erlang was that the particular example used
list comprehensions, and I wondered how you could use Perl to do the
same kind of job, and recursion was as close as i could come to
Erlang's list comprehensions.
In one sense, this thread is simply an idle conversation, something
that you kick around in the break room. In another sense, discussing
how a particular algorithm can be implemented in Perl (or any other
language) is the kind of thing that 'sharpens the axe.'
If you think it's 'incoherent babble' you are free to ignore the
thread. If you think you can code a recursive Pythagorean triple
finder in Perl, you are welcome to try.
CC.
------------------------------
Date: Fri, 18 Mar 2011 09:16:16 +0000
From: bugbear <bugbear@trim_papermule.co.uk_trim>
Subject: Re: recursive Pythagorian triples
Message-Id: <ZtednZg1KtV9vx7QnZ2dnUVZ8mOdnZ2d@brightview.co.uk>
ccc31807 wrote:
>
> If you think it's 'incoherent babble' you are free to ignore the
> thread. If you think you can code a recursive Pythagorean triple
> finder in Perl, you are welcome to try.
Well it would be trivial (and opintless) to express
the nested loops in a recursive form. Would that satisfy
your request>
BugBear
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
Administrivia:
To submit articles to comp.lang.perl.announce, send your article to
clpa@perl.com.
Back issues are available via anonymous ftp from
ftp://cil-www.oce.orst.edu/pub/perl/old-digests.
#For other requests pertaining to the digest, send mail to
#perl-users-request@ruby.oce.orst.edu. Do not waste your time or mine
#sending perl questions to the -request address, I don't have time to
#answer them even if I did know the answer.
------------------------------
End of Perl-Users Digest V11 Issue 3325
***************************************
