[32118] in Perl-Users-Digest
Perl-Users Digest, Issue: 3383 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Fri May 13 09:09:25 2011
Date: Fri, 13 May 2011 06:09:06 -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, 13 May 2011 Volume: 11 Number: 3383
Today's topics:
help!!! <ralph@happydays.com>
Re: piping a vraiable content through a filter <hhr-m@web.de>
Re: piping a vraiable content through a filter <derykus@gmail.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
Rounding issue with defined outcome <bart@nijlen.com>
Re: Rounding issue with defined outcome <NoSpamPleaseButThisIsValid3@gmx.net>
Re: Rounding issue with defined outcome <tadmc@seesig.invalid>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Fri, 13 May 2011 08:49:47 -0400
From: Ralph Malph <ralph@happydays.com>
Subject: help!!!
Message-Id: <70783$4dcd28e9$ce534406$27576@news.eurofeeds.com>
My script isn't working can someone here help me?
On 5/13/2011 3:14 AM, tadmc@seesig.invalid wrote:
> Outline
> Before posting to comp.lang.perl.misc
> Must
> - Check the Perl Frequently Asked Questions (FAQ)
> - Check the other standard Perl docs (*.pod)
> Really Really Should
> - Lurk for a while before posting
> - Search a Usenet archive
> If You Like
> - Check Other Resources
> Posting to comp.lang.perl.misc
> Is there a better place to ask your question?
> - Question should be about Perl, not about the application area
> How to participate (post) in the clpmisc community
> - Carefully choose the contents of your Subject header
> - Use an effective followup style
> - Speak Perl rather than English, when possible
> - Ask perl to help you
> - Do not re-type Perl code
> - Provide enough information
> - Do not provide too much information
> - Do not post binaries, HTML, or MIME
> Social faux pas to avoid
> - Asking a Frequently Asked Question
> - Asking a question easily answered by a cursory doc search
> - Asking for emailed answers
> - Beware of saying "doesn't work"
> - Sending a "stealth" Cc copy
> Be extra cautious when you get upset
> - Count to ten before composing a followup when you are upset
> - Count to ten after composing and before posting when you are upset
> -----------------------------------------------------------------
>
> Posting Guidelines for comp.lang.perl.misc ($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
> help them learn how to post, rather than assume that they do
> know and are being the "bad kind" of Lazy.
>
> 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_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.
>
------------------------------
Date: Fri, 13 May 2011 11:11:52 +0200
From: Helmut Richter <hhr-m@web.de>
Subject: Re: piping a vraiable content through a filter
Message-Id: <alpine.LNX.2.00.1105131100511.5121@lxhri02.ws.lrz.de>
On Thu, 12 May 2011, Rainer Weikusat wrote:
> Helmut Richter <hhr-m@web.de> writes:
>> I have a filter program "filter" which reads from STDIN and writes to
>> STDOUT. Now I have in a Perl script a variable $filter_in with data
>> that have to be transformed to $filter_out. An obvious ways to do that
>> would be
>>
>> use File::Temp qw/tempfile/;
>> ($fh, $fpath) = tempfile();
>> binmode($fh, ":utf8" );
>> print ($fh $filter_in);
>> close ($fh);
>> open (FILTER, "filter <$fpath |");
>> read (FILTER [...]
>>
>> Can it be done without creating a temporary file?
>
> Have a look at IPC::Open3(3pm).
Thanks, this is a valuable hint. There is also
http://perldoc.perl.org/perlipc.html#Bidirectional-Communication-with-Another-Process
with a little more explanation.
In my intended application, things are much simpler: there is no real
two-way communication. The input data is sent once, and the output data is
received once. Without the buffering problems, things would be as simple as
use IPC::Open2;
$stuff = 'x' x $ARGV[0];
$pid = open2($child_out, $child_in, "cat");
print ($child_in "$stuff");
close $child_in;
$got = <$child_out>;
close $child_out;
print "$ARGV[0]\n";
if ($stuff eq $got) {
print "okay\n";
} else {
print "wrong\n";
};
The simple buffered "cat" was chosen deliberately because I do not make
assumptions on the behaviour of the child process.
Just trying out, things went well as long data was shorter than 135168
bytes. This is *much* more than what I need. Now there are two ways to go
on:
- Either enhance the logic of the program that it will work for arbitrary
length of data.
- Or make sure the program will abort instead of hang if input is too
long. That's not really elegant, but entirely fine for the purpose. If it
saves me from programming a lot of things I'll never need ...
Any more hints?
--
Helmut Richter
------------------------------
Date: Fri, 13 May 2011 03:36:06 -0700 (PDT)
From: "C.DeRykus" <derykus@gmail.com>
Subject: Re: piping a vraiable content through a filter
Message-Id: <be971f72-01a4-4078-9fcc-2c30fbb88219@q14g2000prh.googlegroups.com>
On May 13, 2:11=A0am, Helmut Richter <hh...@web.de> wrote:
> On Thu, 12 May 2011, Rainer Weikusat wrote:
> > Helmut Richter <hh...@web.de> writes:
> >> I have a filter program "filter" which reads from STDIN and writes to
> >> STDOUT. Now I have in a Perl script a variable $filter_in with data
> >> that have to be transformed to $filter_out. An obvious ways to do that
> ...
>
> ...
> Just trying out, things went well as long data was shorter than 135168
> bytes. This is *much* more than what I need. Now there are two ways to go
> on:
>
> =A0 - Either enhance the logic of the program that it will work for arbit=
rary
> length of data.
>
> =A0 - Or make sure the program will abort instead of hang if input is too
> long. That's not really elegant, but entirely fine for the purpose. If it
> saves me from programming a lot of things I'll never need ...
>
> Any more hints?
IPC::Run is quite a bit more versatile than
than IPC:OpenX pair and should help with the
buffering issues as I recall.
--
Charles DeRykus
------------------------------
Date: Fri, 13 May 2011 02:14:45 -0500
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
Message-Id: <doudnZ0neuz4R1HQnZ2dnUVZ5jGdnZ2d@giganews.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($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
help them learn how to post, rather than assume that they do
know and are being the "bad kind" of Lazy.
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_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.
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clpmisc is a text only newsgroup. If you have images or binaries
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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: Fri, 13 May 2011 04:19:39 -0700 (PDT)
From: Bart Van der Donck <bart@nijlen.com>
Subject: Rounding issue with defined outcome
Message-Id: <a9187bbc-3054-432e-a620-dfacbf657f4d@g12g2000yqd.googlegroups.com>
Hello,
I have to deal with a rounding issue which basically goes back to high-
precision calculations. The issue is that the outcome is already known
and should match.
----------------------------------------------------------------
Code:
----------------------------------------------------------------
#!/usr/bin/perl
use strict;
use warnings;
my $TOTEXC = 0;
my $TOTINC = 0;
my $TOTTAX = 0;
my @products = ( # product name, price, tax%, quantity
'Screen|506.21|21|4',
'Cables|425.50|21|5',
'Server|585.26|21|1',
'Battery|58.62|21|3',
'Keyb.|44.46|21|2',
'Mouse|15.25|21|6',
'Battery|66.03|21|5'
);
my $percent = 1.2958684232587526; # commission dealer
my $factor = 0.8567; # some fixed factor
print qq{\nPROD\tPRICE\tQUANT\tNET\tTAX\tBRUT\n};
for (@products)
{
my ($prodname, $price, $tax, $quantity) = split /\|/, $_;
$price = ( $price + ($price * $factor / 100) ) * $percent;
my $net = $price * $quantity;
my $brut = $net * ( 1 + ($tax / 100));
$TOTEXC+= $net;
$TOTINC+= $brut;
$TOTTAX+= $brut - $net;
$_ = sprintf("%.2f", $_) for ($price, $net, $brut);
print qq{$prodname\t$price\t$quantity\t$net\t$tax%\t$brut\n};
}
$_ = sprintf("%.2f", $_) for ($TOTEXC, $TOTINC, $TOTTAX);
print qq{\nNet: $TOTEXC\nTax: $TOTTAX\nBrut: $TOTINC\n};
----------------------------------------------------------------
Output:
----------------------------------------------------------------
PROD PRICE QUANT NET TAX BRUT
Screen 661.60 4 2646.41 21% 3202.15
Cables 556.12 5 2780.58 21% 3364.50
Server 764.92 1 764.92 21% 925.55
Battery 76.61 3 229.84 21% 278.11
Keyb. 58.11 2 116.22 21% 140.62
Mouse 19.93 6 119.59 21% 144.70
Battery 86.30 5 431.50 21% 522.11
Net: 7089.05
Tax: 1488.70
Brut: 8577.74
----------------------------------------------------------------
Questions:
----------------------------------------------------------------
- Is there any way to perform the calculations at extreme
high precision, so that all caculated alphanumerics match ?
- I have a known outcome (let's say eg. 8577.77) which was
done already in javascript by another application; is there
a way to guarantee that both outcomes are identical ?
- I have the feeling that this is maybe a common situation,
are there 'classical' approaches for this kind of things ?
- If I want to manually check the order, the calculations
must match (e.g. 'Net'+'Tax' must equal to 'Brut')
Thank you,
--
Bart
------------------------------
Date: Fri, 13 May 2011 13:39:56 +0200
From: Wolf Behrenhoff <NoSpamPleaseButThisIsValid3@gmx.net>
Subject: Re: Rounding issue with defined outcome
Message-Id: <4dcd1891$0$6972$9b4e6d93@newsspool4.arcor-online.net>
On 13.05.2011 13:19, Bart Van der Donck wrote:
> Hello,
>
> I have to deal with a rounding issue which basically goes back to high-
> precision calculations. The issue is that the outcome is already known
> and should match.
>
> ----------------------------------------------------------------
> Questions:
> ----------------------------------------------------------------
>
> - Is there any way to perform the calculations at extreme
> high precision, so that all caculated alphanumerics match ?
>
> - I have a known outcome (let's say eg. 8577.77) which was
> done already in javascript by another application; is there
> a way to guarantee that both outcomes are identical ?
>
> - I have the feeling that this is maybe a common situation,
> are there 'classical' approaches for this kind of things ?
>
> - If I want to manually check the order, the calculations
> must match (e.g. 'Net'+'Tax' must equal to 'Brut')
Obviously you are doing something with money. In that case you usually
do NOT need extreme high precision because there are defined rules how
and when to round to how many digits.
It might be that you need to round to 2 (or 4) digits behind the decimal
point after each step.
So I can only give the advice to really look into the law how to add the
tax correctly and to find out what the contract with the commission
dealer really says.
Wolf
------------------------------
Date: Fri, 13 May 2011 06:48:25 -0500
From: Tad McClellan <tadmc@seesig.invalid>
Subject: Re: Rounding issue with defined outcome
Message-Id: <slrnisq6bc.8el.tadmc@tadbox.sbcglobal.net>
Bart Van der Donck <bart@nijlen.com> wrote:
> my $percent = 1.2958684232587526; # commission dealer
Add this, and look carefully at the output it makes:
printf "%30.20f\n", $percent;
So things are wrong even before you start making any calculations...
> - I have the feeling that this is maybe a common situation,
Yes it is, and it is not restricted to Perl.
This problem applies to how numbers are stored in computers.
> are there 'classical' approaches for this kind of things ?
perldoc perlnumber
See also: What Every Computer Scientist Should Know About Floating-Point
Arithmetic
http://download.oracle.com/docs/cd/E19957-01/806-3568/ncg_goldberg.html
--
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: 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:
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------------------------------
End of Perl-Users Digest V11 Issue 3383
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