[24984] in Perl-Users-Digest
Perl-Users Digest, Issue: 7234 Volume: 10
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Oct 12 14:12:03 2004
Date: Tue, 12 Oct 2004 11:10:14 -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 Tue, 12 Oct 2004 Volume: 10 Number: 7234
Today's topics:
Re: How do I merge two arrays or two strings? (Anno Siegel)
if {} vs eval {} if <nntp@rogers.com>
Re: if {} vs eval {} if <jwillmore@adelphia.net>
Lagrange Interpolating Polynomial <goofy_headed_punk@msn.com>
Re: Lagrange Interpolating Polynomial <matternc@comcast.net>
Re: Lagrange Interpolating Polynomial <postmaster@castleamber.com>
Re: Lagrange Interpolating Polynomial <usenet@morrow.me.uk>
Re: Lagrange Interpolating Polynomial (Anno Siegel)
Re: localizing %SIG handlers (Anno Siegel)
Re: perl-parser? or a perl 2 java converter? <usenet@morrow.me.uk>
Perls system() call fails in a cgi-file running on win2 (Mr. Zeus)
Re: Perls system() call fails in a cgi-file running on <usa1@llenroc.ude.invalid>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@augustmail.com
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: 12 Oct 2004 12:30:37 GMT
From: anno4000@lublin.zrz.tu-berlin.de (Anno Siegel)
Subject: Re: How do I merge two arrays or two strings?
Message-Id: <ckgipd$gi8$2@mamenchi.zrz.TU-Berlin.DE>
Jay Tilton <tiltonj@erols.com> wrote in comp.lang.perl.misc:
> "nntp" <nntp@rogers.com> wrote:
>
> : Let's say I have two arrays, one has N elements and the other has M. Both N
> : and M vary. I want to merge the two like you shuffle two decks of cards.
> : from
> : 1 2 3 4 5 6 7 8
> : a b c d e f g h
> : to
> : 12a34bc5def78gh
> :
>
> #!perl
> use strict;
> use warnings;
> use List::Util 'shuffle';
> my @a = qw(1 2 3 4 5 6 7 8);
> my @b = qw(a b c d e f g h);
> my @c = map shift @{[\(@a, @b)]->[$_]}, shuffle( (0) x @a, (1) x @b );
> __END__
>
Ah... using shuffle(). Nice solution.
Anno
------------------------------
Date: Tue, 12 Oct 2004 08:35:38 -0400
From: "nntp" <nntp@rogers.com>
Subject: if {} vs eval {} if
Message-Id: <O4ydndQJyaQrUvbcRVn-sg@rogers.com>
if (something) { do it;}
vs
eval {do it;} if (something);
Are there any difference? Is eval simply a error catcher?
I don't understand the part in perldoc:
In the second form, the code within the BLOCK is parsed only
once--at the same time the code surrounding the eval itself was
parsed--and executed within the context of the current Perl
program. This form is typically used to trap exceptions more
efficiently than the first (see below), while also providing the
benefit of checking the code within BLOCK at compile time.
eval "\$$x++"; # CASE 5
$$x++; # CASE 6
What do those two cases do? add 1 to x then...? Why do we need eval in case
5?
------------------------------
Date: Tue, 12 Oct 2004 10:04:48 -0400
From: James Willmore <jwillmore@adelphia.net>
Subject: Re: if {} vs eval {} if
Message-Id: <ztOdnYSj-p_zefbcRVn-qA@adelphia.com>
nntp wrote:
> if (something) { do it;}
> vs
> eval {do it;} if (something);
>
> Are there any difference? Is eval simply a error catcher?
More or less :-) Read on ...
> I don't understand the part in perldoc:
>
> In the second form, the code within the BLOCK is parsed only
> once--at the same time the code surrounding the eval itself was
> parsed--and executed within the context of the current Perl
> program. This form is typically used to trap exceptions more
> efficiently than the first (see below), while also providing the
> benefit of checking the code within BLOCK at compile time.
>
> eval "\$$x++"; # CASE 5
"Does this reference exist (\$$x++)?" is what's going on in this case.
If it does and we can increment by 1, then the 'eval' succeeds and we
move on. If it doesn't or we can't increment by 1, then we can see what
happened in the special variable '$@' and deal with this run-time
occurrence.
> $$x++; # CASE 6
The same applies here, but if we get a run time error, we 'die'.
> What do those two cases do? add 1 to x then...? Why do we need eval in case
> 5?
I'm going to give, what I hope will be, a practical application of
'eval' for review.
Suppose you have an application that accepts user input. The
application doesn't rely upon the user input, but does need to do
something if it does get user input. The application should not die if
the user has elected to give invalid input. So, how do we do this? We
can use 'eval' to prevent a fatal run-time error.
Example:
=begin
#!/usr/bin/perl
use warnings;
use strict;
my $result = 0;
my $user_input = 0;
eval {
$result = 1 / $user_input;
};
if($@) {
print <<EOP;
User has entered zero (0) for a value.
We would 'die' here, but instead we will let you know and move on.
EOP
}
print "Program has finished with a result of $result\n";
=cut
As you can see, we "evaluate" the user input. If we get a run-time
error as a result of the user input, we print a message and move on.
But what happens if we don't use 'eval'? Well, let's comment out the
lines related to our use of 'eval' and see.
=begin
#!/usr/bin/perl
use warnings;
use strict;
my $result = 0;
my $user_input = 0;
#eval {
$result = 1 / $user_input;
#};
#if($@) {
# print <<EOP;
#User has entered zero (0) for a value.
#We would 'die' here, but instead we will let you know and move on.
#EOP
#}
print "Program has finished with a result of $result\n";
=cut
We get "Illegal division by zero at test_eval.pl line 10." and the
application ends. Remember the requirements of out example application
- we don't *have* to have user input to do what we need to do.
So, for the first part of your post, this is the reason for 'eval'. If
we try to evaluate a variable, expression, etc. that *may* give use a
run-time error, we can use 'eval' to evaluate the results and then do
something more appropriate than just 'die' This is similar to Java's
try-catch-finally exception catching mechanism (if this helps :-) ).
HTH
Jim
------------------------------
Date: Mon, 11 Oct 2004 23:57:37 -0500
From: Brian Troutwine <goofy_headed_punk@msn.com>
Subject: Lagrange Interpolating Polynomial
Message-Id: <pan.2004.10.12.04.57.36.150719@msn.com>
Here's my finished Lagrange polynomial finder. It runs, and unless a
stress test suggests otherwise (to be performed overnight), works
excellently, but merely is really slow. Any suggestions to get it running
faster?
#!/usr/bin/perl
use diagnostics;
use strict;
use Getopt::Std;
use Math::BigRat;
#Variables
#zork is a common array to allow for different input sources
#The starting zero allows us to use this algorithm for as few
#as two input values. Hopefully the next version will allow
#for one term, but that's trivial to do by hand.
my @zork = (0);
our @equation = (0);
our @poly1 = ("");
our @poly2 = ("");
our $opt_f = "";
getopt("f");
#Opens pipe if no -f used
if($opt_f eq ""){
foreach my $foo (<>){
push @zork, Math::BigRat->new($foo);
}}
#Opens file specified by -f
else{
open(FOO, "<$opt_f") || die("File does not exist.");
my @bar=<FOO>;
close(FOO);
foreach my $bar (@bar){
push @zork, Math::BigRat->new($bar);
}}
chomp @zork;
#$i represents the number of the term we're working with.
for( my $i = 0; $i <= $#zork; $i++){
my $thisy = Math::BigRat->new($zork[$i]);
#Creates denominator for each term.
my $denominator = Math::BigRat->new('1/1');
for( my $j = 0; $j <= $#zork; $j++){
if ($j != $i){
$denominator *= ($i - $j);
}}
#Makes array of n's in (x-n) where n is
#all integers from 0 to $#zork except
#$i.
my @numerator;
for( my $k = 0; $k <= $#zork; $k++){
if ($k != $i){
push @numerator,(-$k);
}}
#Computes numerator as polynomial
for(my $l = 0; $l<=$#numerator; $l++){
#The polynomials will be arrays in which any position
#will hold the coefficient of the corresponding power
#of x. For example, the first position (0) will hold
#the constant (the coefficient for x^0).
if($l == 0){
@poly1 = (0,1);
$l++;
}
@poly2 = ($numerator[$l],1);
my @neweq = (0);
#To multiply our polynomials, we take each of the
#terms of the first polynomial, and multiply them
#by each of the terms of the second, and add the
#resulting coefficient to the sum of their positions
for(my $m=0; $m<=$#poly1; $m++){
for(my $n=0; $n<=$#poly2; $n++){
$neweq[$m+$n] += Math::BigRat->new($poly1[$m] * $poly2[$n]);
}}
#Set poly1 to the new equation for the next loop through
@poly1 = @neweq;
}
#To avoid decimals, we've used fractions to multiply
#each of our terms by.
for(my $o=0; $o<=$#poly1; $o++){
$poly1[$o] *= $thisy / $denominator;
}
#Adding up our polynomials, because we want to simplify
for(my $p=0; $p<=$#poly1; $p++){
$equation[$p] += $poly1[$p];
}
}
my $flag = 0;
#Output
for(my $q = $#equation; $q >= 0; $q--){
#Doesn't output zero terms
unless($equation[$q] == 0){
#No plus if it's first or negative, it just makes sense
if (($flag != 0) && ($equation[$q] > 0)){
print "+";
}
print $equation[$q];
#Prints x except for on constant, and power except for
#first power
unless($q == 0){
print "x";
}
if($q > 1){
print "^$q";
}
print "\n\n";
$flag++;
}}
#In case somebody happens to only input zeroes, we don't want
#to leave that poor bastard with no output.
if ($flag == 0){
print "0\n";
}
Thanks.
------------------------------
Date: Tue, 12 Oct 2004 11:20:34 -0400
From: Chris Mattern <matternc@comcast.net>
Subject: Re: Lagrange Interpolating Polynomial
Message-Id: <1s6dnW-B3JXfa_bcRVn-tQ@comcast.com>
Anno Siegel wrote:
> Brian Troutwine <goofy_headed_punk@msn.com> wrote in comp.lang.perl.misc:
>> Here's my finished Lagrange polynomial finder. It runs, and unless a
>> stress test suggests otherwise (to be performed overnight), works
>> excellently, but merely is really slow. Any suggestions to get it running
>> faster?
>
> Not significantly. You have a few unnecessary calls to
> Math::BigRat->new, but otherwise you seem to do what must be done.
>
>> #!/usr/bin/perl
>> use diagnostics;
>> use strict;
>> use Getopt::Std;
>> use Math::BigRat;
>
> No warnings?
>
He's got use diagnostics. Use warnings would be redundant.
--
Christopher Mattern
"Which one you figure tracked us?"
"The ugly one, sir."
"...Could you be more specific?"
------------------------------
Date: 12 Oct 2004 05:59:43 GMT
From: John Bokma <postmaster@castleamber.com>
Subject: Re: Lagrange Interpolating Polynomial
Message-Id: <Xns9580A1FB9A62castleamber@130.133.1.4>
Brian Troutwine wrote:
> Here's my finished Lagrange polynomial finder. It runs, and unless a
> stress test suggests otherwise (to be performed overnight), works
> excellently, but merely is really slow. Any suggestions to get it running
> faster?
[ snip ]
> for(my $o=0; $o<=$#poly1; $o++){
> $poly1[$o] *= $thisy / $denominator;
> }
$_ *= $thisy / $denominator for @poly1;
?
I see a lot of indexed looping, probably can be rewritten as the one above.
--
John MexIT: http://johnbokma.com/mexit/
personal page: http://johnbokma.com/
Experienced programmer available: http://castleamber.com/
Happy Customers: http://castleamber.com/testimonials.html
------------------------------
Date: Tue, 12 Oct 2004 12:48:52 +0100
From: Ben Morrow <usenet@morrow.me.uk>
Subject: Re: Lagrange Interpolating Polynomial
Message-Id: <4uss32-cl5.ln1@osiris.mauzo.dyndns.org>
Quoth Brian Troutwine <goofy_headed_punk@msn.com>:
> Here's my finished Lagrange polynomial finder. It runs, and unless a
> stress test suggests otherwise (to be performed overnight), works
> excellently, but merely is really slow. Any suggestions to get it running
> faster?
>
> #!/usr/bin/perl
> use diagnostics;
> use strict;
> use Getopt::Std;
> use Math::BigRat;
I'm not competent to comment on the algorithm (and anyway Anno already
has) but I would suspect the default BigRat implementation is the
slowest. You could try changing to ::GMP or something to see if it makes
a difference.
Ben
--
If you put all the prophets, | You'd have so much more reason
Mystics and saints | Than ever was born
In one room together, | Out of all of the conflicts of time.
ben@morrow.me.uk The Levellers, 'Believers'
------------------------------
Date: 12 Oct 2004 10:37:13 GMT
From: anno4000@lublin.zrz.tu-berlin.de (Anno Siegel)
Subject: Re: Lagrange Interpolating Polynomial
Message-Id: <ckgc4p$d72$1@mamenchi.zrz.TU-Berlin.DE>
Brian Troutwine <goofy_headed_punk@msn.com> wrote in comp.lang.perl.misc:
> Here's my finished Lagrange polynomial finder. It runs, and unless a
> stress test suggests otherwise (to be performed overnight), works
> excellently, but merely is really slow. Any suggestions to get it running
> faster?
Not significantly. You have a few unnecessary calls to
Math::BigRat->new, but otherwise you seem to do what must be done.
> #!/usr/bin/perl
> use diagnostics;
> use strict;
> use Getopt::Std;
> use Math::BigRat;
No warnings?
> #Variables
> #zork is a common array to allow for different input sources
> #The starting zero allows us to use this algorithm for as few
> #as two input values. Hopefully the next version will allow
> #for one term, but that's trivial to do by hand.
> my @zork = (0);
> our @equation = (0);
> our @poly1 = ("");
> our @poly2 = ("");
> our $opt_f = "";
> getopt("f");
It is preferable to declare variables immediately before their first
use.
> #Opens pipe if no -f used
> if($opt_f eq ""){
> foreach my $foo (<>){
> push @zork, Math::BigRat->new($foo);
> }}
>
> #Opens file specified by -f
> else{
> open(FOO, "<$opt_f") || die("File does not exist.");
> my @bar=<FOO>;
> close(FOO);
> foreach my $bar (@bar){
> push @zork, Math::BigRat->new($bar);
> }}
>
> chomp @zork;
@zork is an array of BigRat's. Chomping makes no sense.
> #$i represents the number of the term we're working with.
> for( my $i = 0; $i <= $#zork; $i++){
> my $thisy = Math::BigRat->new($zork[$i]);
$zork[ $i] is already a BigRat object. No need for ->new.
> #Creates denominator for each term.
> my $denominator = Math::BigRat->new('1/1');
> for( my $j = 0; $j <= $#zork; $j++){
> if ($j != $i){
> $denominator *= ($i - $j);
> }}
The for-loop can be written:
$denominator *= ( $i - $_) for grep $_ != $i, 0 .. $#zork;
>
> #Makes array of n's in (x-n) where n is
> #all integers from 0 to $#zork except
> #$i.
> my @numerator;
> for( my $k = 0; $k <= $#zork; $k++){
> if ($k != $i){
> push @numerator,(-$k);
> }}
Similarly:
my @numerator = map -$_, grep $_ != $i, 0 .. $#zork;
> #Computes numerator as polynomial
> for(my $l = 0; $l<=$#numerator; $l++){
>
> #The polynomials will be arrays in which any position
> #will hold the coefficient of the corresponding power
> #of x. For example, the first position (0) will hold
> #the constant (the coefficient for x^0).
> if($l == 0){
> @poly1 = (0,1);
> $l++;
> }
Doing this inside the loop is awkward. Initialize $poly1 before
the loop, and start at $l = 1.
> @poly2 = ($numerator[$l],1);
>
> my @neweq = (0);
>
> #To multiply our polynomials, we take each of the
> #terms of the first polynomial, and multiply them
> #by each of the terms of the second, and add the
> #resulting coefficient to the sum of their positions
> for(my $m=0; $m<=$#poly1; $m++){
> for(my $n=0; $n<=$#poly2; $n++){
> $neweq[$m+$n] += Math::BigRat->new($poly1[$m] * $poly2[$n]);
> }}
You are using a full-fledged multiplication routine (which, in a
greater scheme of things, would deserve to be a subroutine). But
all you do is multiply a polynomial with a linear expression (x - a).
That could be done in an ad-hoc manner thusly:
my @neweq = map $_ * $numerator[ $l], @poly1;
$neweq[ $_ + 1] += $poly1[ $_] for 0 .. $#poly1;
> #Set poly1 to the new equation for the next loop through
> @poly1 = @neweq;
> }
>
> #To avoid decimals, we've used fractions to multiply
> #each of our terms by.
> for(my $o=0; $o<=$#poly1; $o++){
> $poly1[$o] *= $thisy / $denominator;
> }
$_ *= $thisy / $denominator for @poly1;
> #Adding up our polynomials, because we want to simplify
> for(my $p=0; $p<=$#poly1; $p++){
> $equation[$p] += $poly1[$p];
> }
$equation[ $_] += $poly1[ $_] for 0 .. $#poly1;
> }
>
> my $flag = 0;
That belongs to the output routine and should be below the
comment.
> #Output
I'd use an auxiliary routine to format one term for the output.
Quite generally, your code could gain a lot if you used more
subroutines to factor out common operations.
> for(my $q = $#equation; $q >= 0; $q--){
>
> #Doesn't output zero terms
> unless($equation[$q] == 0){
>
> #No plus if it's first or negative, it just makes sense
> if (($flag != 0) && ($equation[$q] > 0)){
> print "+";
> }
> print $equation[$q];
>
> #Prints x except for on constant, and power except for
> #first power
> unless($q == 0){
> print "x";
> }
> if($q > 1){
> print "^$q";
> }
> print "\n\n";
> $flag++;
> }}
>
> #In case somebody happens to only input zeroes, we don't want
> #to leave that poor bastard with no output.
> if ($flag == 0){
> print "0\n";
> }
# collect non-zero terms
my @terms = grep $_->[ 0], map [ $equation[ $_], $_], 0 .. $#equation;
my $str = '';
$str .= term_to_str( @$_) for reverse @terms;
$str =~ s/^\+//;
print $str || '0';
sub term_to_str {
my ( $fac, $exp) = @_;
my $power = '';
$power .= 'x' if $exp;
$power .= "^$exp" if $exp != 1;
$fac = "+$fac" unless $fac < 0;
"$fac$power\n\n";
}
Anno
------------------------------
Date: 12 Oct 2004 07:22:31 GMT
From: anno4000@lublin.zrz.tu-berlin.de (Anno Siegel)
Subject: Re: localizing %SIG handlers
Message-Id: <ckg0nn$4vm$1@mamenchi.zrz.TU-Berlin.DE>
William Ahern <william@wilbur.25thandClement.com> wrote in comp.lang.perl.misc:
> Anno Siegel <anno4000@lublin.zrz.tu-berlin.de> wrote:
> <snip>
> > The assumption is that $SIG{ HUP} is either the global or the local
> > handler at all times, so the (HUP) signal will always be caught, but
> > apparently that assumption isn't true. "local" sets the handler
> > to undef, and then "=" sets it to \ &local_handler. It is quite
> > possible for a signal to arrive when the hander is undefined, which
> > ends the program through an uncaught signal. The following code
> > shows this:
>
> Are you using Perl >= 5.7.3? I'm a little surprised (not much, though) that
> Perl--with it's delayed signal handling--would actually uninstall a
> signal handler rather than mimic an uninstalled handler.
I've seen the behavior with 5.8.1 and 5.8.4.
Anno
------------------------------
Date: Tue, 12 Oct 2004 12:41:04 +0100
From: Ben Morrow <usenet@morrow.me.uk>
Subject: Re: perl-parser? or a perl 2 java converter?
Message-Id: <gfss32-cl5.ln1@osiris.mauzo.dyndns.org>
Quoth bboett@adlp.org:
>
> i have prototyped some applications in perl, and now want to rewrite
> them in java...
>
> rewriting from scratch would be quite some work, thus i am looking if
> there are some ready means to convert the perl code (as far as possible)
> into java code...
AFAIK there aren't any. Perl->* convertors are provided by the O and
B::* modules, but the ones such as B::C and B::CC that actually produce
working programs in other languages have pretty much all been put on
hold, and it's not recommended you use them any more as they were never
properly finished.
You could always write one, of course :)
> alternatively, is there a way to instruct the perl parser to issue the
> parsed perl-tree before execution?
You could try B::Concise, but I really don't know what you think you
might do with the information.
> or if even this isn't possible, the reflection possibilities in perl
> seem a bit limited,
<standard answer for any advanced OO in perl5>
Yes, they are; this will be fixed (with a vengeance) in perl6, but don't
hold your breath.
> is there a way to ask a an instance of an object the
> list of implemented methods, and possibly only the methods overwritten
> in the current class?
Not in general. You could walk the namespace and get all the defined
subs with something like
no strict 'refs';
$\ = "\n";
my $class = 'My::Class';
for my $i (keys %{"$class\::"}) {
print $i if exists &{"$class\::$i"};
}
but this
1. won't distingish methods from functions
2. won't distinguish public/private methods (the concept doesn't exist
in Perl)
3. won't find inherited methods (though you could check @ISA and
recursively walk those classes as well)
4. most importantly, won't find AUTOLOADed methods unless they've been
stubbed, which is usual for AUTOLOADed functions but not for methods as
you don't need to.
Ben
--
For the last month, a large number of PSNs in the Arpa[Inter-]net have been
reporting symptoms of congestion ... These reports have been accompanied by an
increasing number of user complaints ... As of June,... the Arpanet contained
47 nodes and 63 links. [ftp://rtfm.mit.edu/pub/arpaprob.txt] * ben@morrow.me.uk
------------------------------
Date: 12 Oct 2004 06:06:59 -0700
From: mister_x_sun@hotmail.com (Mr. Zeus)
Subject: Perls system() call fails in a cgi-file running on win2k and apache
Message-Id: <e5b9e7c7.0410120506.6c7f0093@posting.google.com>
I am running a UseMod wiki and tried to implement some system calls
using the perl command system(@args). In my case it was a call of an
executable file.
Path to the file was fully given as well as the proper settings of
@args.
Independant of the function (dos-command or exe) I am calling it
doesn't work.
The system I am using is:
W2K SR2
apache 2.0.50 (win32)
Perl 5.8.4
Are there additional mods necessary in the apache config?
What to do exactly?
Thanks for your help
Zeus
------------------------------
Date: 12 Oct 2004 13:43:16 GMT
From: "A. Sinan Unur" <usa1@llenroc.ude.invalid>
Subject: Re: Perls system() call fails in a cgi-file running on win2k and apache
Message-Id: <Xns9580632ADF63Dasu1cornelledu@132.236.56.8>
mister_x_sun@hotmail.com (Mr. Zeus) wrote in
news:e5b9e7c7.0410120506.6c7f0093@posting.google.com:
> I am running a UseMod wiki and tried to implement some system calls
> using the perl command system(@args). In my case it was a call of an
> executable file.
> Path to the file was fully given as well as the proper settings of
> @args.
> Independant of the function (dos-command or exe) I am calling it
> doesn't work.
Please read the posting guidelines posted here frequently. You have given
no useful information and you did not describe your problem (does not work
does not count).
> The system I am using is:
> W2K SR2
> apache 2.0.50 (win32)
> Perl 5.8.4
Good for you.
> Are there additional mods necessary in the apache config?
> What to do exactly?
>
> Thanks for your help
> Zeus
Find a telepath.
Sinan.
------------------------------
Date: Tue, 12 Oct 2004 02:23:12 -0500
From: tadmc@augustmail.com
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.5 $)
Message-Id: <w-idnQgaSv79G_bcRVn-rw@august.net>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($Revision: 1.5 $)
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://mail.augustmail.com/~tadmc/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
help them learn how to post, rather than assume
A note about technical terms used here:
In this document, we use words like "must" and "should" as
they're used in technical conversation (such as you will
encounter in this newsgroup). When we say that you *must* do
something, we mean that if you don't do that something, then
it's unlikely that you will benefit much from this group.
We're not bossing you around; we're making the point without
lots of words.
Do *NOT* send email to the maintainer of these guidelines. It will be
discarded unread. The guidelines belong to the newsgroup so all
discussion should appear in the newsgroup. I am just the secretary that
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
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_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 <tadmc@augustmail.com> and many others on the
comp.lang.perl.misc newsgroup.
------------------------------
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>
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------------------------------
End of Perl-Users Digest V10 Issue 7234
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