[32018] in Perl-Users-Digest
Perl-Users Digest, Issue: 3282 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Fri Feb 11 06:09:23 2011
Date: Fri, 11 Feb 2011 03:09:09 -0800 (PST)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Fri, 11 Feb 2011 Volume: 11 Number: 3282
Today's topics:
Hashes are good, but not good enough. <nospam.gravitalsun@hotmail.com.nospam>
Re: Hashes are good, but not good enough. <uri@StemSystems.com>
Re: Hashes are good, but not good enough. <nospam.gravitalsun@hotmail.com.nospam>
Re: Hashes are good, but not good enough. <uri@StemSystems.com>
Re: How to exclude action of Find::Find::find in subdir <jimsgibson@gmail.com>
Re: ParseExcel $font->{Color} Question? <justin.1011@purestblue.com>
Posting Guidelines for comp.lang.perl.misc ($Revision: tadmc@seesig.invalid
Re: table --> pre? <rvtol+usenet@xs4all.nl>
Re: table --> pre? <cartercc@gmail.com>
Re: toy list processing problem: collect similar terms <w_a_x_man@yahoo.com>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Fri, 11 Feb 2011 11:13:07 +0200
From: "George Mpouras" <nospam.gravitalsun@hotmail.com.nospam>
Subject: Hashes are good, but not good enough.
Message-Id: <ij2uht$1go1$1@ulysses.noc.ntua.gr>
We all find hashes pretty convenient, and helpful to make things fast; but
the problem with hashes is that they consume too much memory on big trees,
and they are too slow for hundred millions of keys. Try it yourself.
What we need in these situations is something different called DAWG.
Please have a look at this article to understand what I mean.
http://en.wikipedia.org/wiki/DAWG
I tried to implement this DAWG data structure with Perl but I found it VERY
difficult.
What are your thoughts about the necessity of this new data structure.
------------------------------
Date: Fri, 11 Feb 2011 04:18:47 -0500
From: "Uri Guttman" <uri@StemSystems.com>
Subject: Re: Hashes are good, but not good enough.
Message-Id: <87y65n7wug.fsf@quad.sysarch.com>
>>>>> "GM" == George Mpouras <nospam.gravitalsun@hotmail.com.nospam> writes:
GM> We all find hashes pretty convenient, and helpful to make things
GM> fast; but the problem with hashes is that they consume too much
GM> memory on big trees, and they are too slow for hundred millions of
GM> keys. Try it yourself.
no need to try it. that large a hash is foolish in all ways. you are
choosing the wrong tool.
GM> What we need in these situations is something different called DAWG.
GM> Please have a look at this article to understand what I mean.
GM> http://en.wikipedia.org/wiki/DAWG
from that article:
for a query operation that tests whether a given string belongs
to the set in time proportional to its length
do you understand O() theory? hashes are close to O(1) while DAWG is
effectively O(N). not even close.
GM> I tried to implement this DAWG data structure with Perl but I
GM> found it VERY difficult.
then you also have difficulty understanding the speed
differences. undoubtedly you have run into thrashing which is not a hash
problem but a ram problem.
GM> What are your thoughts about the necessity of this new data structure.
not needed in core perl. hashes are far faster. perl has always traded
off ram size for more speed in its design. a DAWG will never be able to
replace a hash for that reason. by far most hashes fit in ram just
fine. if you are scaling that large you likely need a db or something
disk based anyhow.
uri
--
Uri Guttman ------ uri@stemsystems.com -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------
------------------------------
Date: Fri, 11 Feb 2011 12:13:07 +0200
From: "George Mpouras" <nospam.gravitalsun@hotmail.com.nospam>
Subject: Re: Hashes are good, but not good enough.
Message-Id: <ij3228$1s95$1@ulysses.noc.ntua.gr>
"Uri Guttman" <uri@StemSystems.com> wrote in message
news:87y65n7wug.fsf@quad.sysarch.com...
>>>>>> "GM" == George Mpouras <nospam.gravitalsun@hotmail.com.nospam>
>>>>>> writes:
>
> GM> We all find hashes pretty convenient, and helpful to make things
> GM> fast; but the problem with hashes is that they consume too much
> GM> memory on big trees, and they are too slow for hundred millions of
> GM> keys. Try it yourself.
>
> no need to try it. that large a hash is foolish in all ways. you are
> choosing the wrong tool.
>
> GM> What we need in these situations is something different called DAWG.
>
> GM> Please have a look at this article to understand what I mean.
>
> GM> http://en.wikipedia.org/wiki/DAWG
>
> from that article:
>
> for a query operation that tests whether a given string belongs
> to the set in time proportional to its length
>
>
> do you understand O() theory? hashes are close to O(1) while DAWG is
> effectively O(N). not even close.
>
> GM> I tried to implement this DAWG data structure with Perl but I
> GM> found it VERY difficult.
>
> then you also have difficulty understanding the speed
> differences. undoubtedly you have run into thrashing which is not a hash
> problem but a ram problem.
>
> GM> What are your thoughts about the necessity of this new data
> structure.
>
> not needed in core perl. hashes are far faster. perl has always traded
> off ram size for more speed in its design. a DAWG will never be able to
> replace a hash for that reason. by far most hashes fit in ram just
> fine. if you are scaling that large you likely need a db or something
> disk based anyhow.
>
> uri
>
> --
> Uri Guttman ------ uri@stemsystems.com --------
> http://www.sysarch.com --
> ----- Perl Code Review , Architecture, Development, Training,
> Support ------
> --------- Gourmet Hot Cocoa Mix ----
> http://bestfriendscocoa.com ---------
he millions can also be 2 or 1000 keys. There is something very important
here. DAWG structures are much smaller than hashes and searching them is
also faster.
------------------------------
Date: Fri, 11 Feb 2011 05:17:49 -0500
From: "Uri Guttman" <uri@StemSystems.com>
Subject: Re: Hashes are good, but not good enough.
Message-Id: <87lj1m98oi.fsf@quad.sysarch.com>
>>>>> "GM" == George Mpouras <nospam.gravitalsun@hotmail.com.nospam> writes:
GM> he millions can also be 2 or 1000 keys. There is something very important
GM> here. DAWG structures are much smaller than hashes and searching them is
GM> also faster.
not from the descriptions you quoted. you haven't stated you understand
O() theory. if you don't then there is no further discussion here. look
it up and learn it. learn how to properly analyze an algorithm's
performance and how it scales. note that bubble sorts beat out all other
sorts for a handful of elements. yet no sort lib uses the bubble sort.
dawg is linear on the key length. what happens when you have very long
keys? it gets very slow. hashes don't change their speed based on key
length. any tree search is going to be slower in O() than any hash
method. if you don't get that, learn why.
uri
--
Uri Guttman ------ uri@stemsystems.com -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------
------------------------------
Date: Thu, 10 Feb 2011 14:31:27 -0800
From: Jim Gibson <jimsgibson@gmail.com>
Subject: Re: How to exclude action of Find::Find::find in subdirectories with known names?
Message-Id: <100220111431279892%jimsgibson@gmail.com>
In article
<62f2fb2d-25ae-4349-8171-bd397acb8285@s28g2000prb.googlegroups.com>,
vdvorkin <vadim.dvorkin@gmail.com> wrote:
> I must pass through directory tree and to execute some action with
> files, names of which described by regex. I need not do it in
> directories SCCS and VVS, which can be in every subdirectory.
>
> The following code works correctly, does not action ("THE ACTION") in
> unwanted directories, but it pass through every subdirectory. I'd
> would like that it will worked faster, and procedure "wanted" will not
> step inside SCCS and VVS. I have tried for that purpose the
> "untaint_pattern" and "untaint_skip" options but did not success.
> Perhaps I used incorrect values. Or, I do not understand the task of
> the options correctly.
>
> Somebody can suggest to me the decision?
Set the $File::Find::prune variable when you first visit an unwanted
directory, and don't specify the 'bydepth' option (untested):
use File::Find;
sub wanted;
find( {wanted => \&wanted}, '.');
sub wanted
{
if ( m{ / SCCS \z }x || m{ / VVS \z }x )
{
$File::Find::prune = 1;
}else{
# THE ACTION...
}
}
--
Jim Gibson
------------------------------
Date: Fri, 11 Feb 2011 09:50:19 +0000
From: Justin C <justin.1011@purestblue.com>
Subject: Re: ParseExcel $font->{Color} Question?
Message-Id: <rbdf28-n1i.ln1@zem.masonsmusic.co.uk>
On 2011-02-10, Tom <zihav@yahoo.com> wrote:
>>I don't see get_rich_text() as an available method in the
>>Spreadsheet::ParseExcel package. Ah, I see, you're using get_rich_text()
>>which is available in Spreadsheet::ParseExcel::Cell, maybe you should
>>specify that module?
>
> Tried that, no luck. I see it in the Cell.pm file:
>
> # get_rich_text()
> #
> # Returns an array ref of font information about each string block in a "rich",
> # i.e. multi-format, string.
> #
> sub get_rich_text {
>
> my $self = shift;
>
> return $self->{Rich};
> }
>
> but I'm not getting any values back...
I've not investigated very thoroughly, maybe the docs are wrong, but I
created a spreadsheet and ran, as you did, the example, I also included
the Data::Dumper module, and then here is the content of my inner-most
loop:
my $cell = $ws->get_cell( $row, $col );
next unless $cell;
print "Row, Col = ($row, $col)\n";
print "Value = ", $cell->value(), "\n";
print "Dumper = ", Dumper($cell->get_format()), "\n";
print "\n";
The output of that Dumper call should give you enough of a clue to get
what you want.
And if it doesn't, then this should.
my $format = $cell->get_format();
my $colour = $format->{Font}{Color};
Of course, the colour is not named, it's in Excel notation so you'll
have to look it up.
Justin.
--
Justin C, by the sea.
------------------------------
Date: Fri, 11 Feb 2011 02:15:27 -0600
From: tadmc@seesig.invalid
Subject: Posting Guidelines for comp.lang.perl.misc ($Revision: 1.9 $)
Message-Id: <aZCdnc9XGMuCbcnQnZ2dnUVZ5qqdnZ2d@giganews.com>
Outline
Before posting to comp.lang.perl.misc
Must
- Check the Perl Frequently Asked Questions (FAQ)
- Check the other standard Perl docs (*.pod)
Really Really Should
- Lurk for a while before posting
- Search a Usenet archive
If You Like
- Check Other Resources
Posting to comp.lang.perl.misc
Is there a better place to ask your question?
- Question should be about Perl, not about the application area
How to participate (post) in the clpmisc community
- Carefully choose the contents of your Subject header
- Use an effective followup style
- Speak Perl rather than English, when possible
- Ask perl to help you
- Do not re-type Perl code
- Provide enough information
- Do not provide too much information
- Do not post binaries, HTML, or MIME
Social faux pas to avoid
- Asking a Frequently Asked Question
- Asking a question easily answered by a cursory doc search
- Asking for emailed answers
- Beware of saying "doesn't work"
- Sending a "stealth" Cc copy
Be extra cautious when you get upset
- Count to ten before composing a followup when you are upset
- Count to ten after composing and before posting when you are upset
-----------------------------------------------------------------
Posting Guidelines for comp.lang.perl.misc ($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.
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: Thu, 10 Feb 2011 20:11:09 +0100
From: "Dr.Ruud" <rvtol+usenet@xs4all.nl>
Subject: Re: table --> pre?
Message-Id: <4d54384e$0$81485$e4fe514c@news.xs4all.nl>
On 2011-02-10 15:42, hymie! wrote:
> Can somebody recommend to me a perl script or a perl module that
> takes an HTML-formatted<table> and produces a space-formatted
> output that would be suitable for use within a<pre> tag?
>
> I currently have a black-box java script that does this, but doesn't
> do it well, and I don't have the ability to adjust it. At least with a
> perl script, I can probably tweak it to meet my needs.
Or use links/lynx?
--
Ruud
------------------------------
Date: Thu, 10 Feb 2011 13:07:38 -0800 (PST)
From: ccc31807 <cartercc@gmail.com>
Subject: Re: table --> pre?
Message-Id: <1c245cb5-9684-4a3f-a50d-2fa72348188a@y31g2000prd.googlegroups.com>
On Feb 10, 9:42=A0am, hy...@lactose.homelinux.net (hymie!) wrote:
> Greetings.
>
> Can somebody recommend to me a perl script or a perl module that
> takes an HTML-formatted <table> and produces a space-formatted
> output that would be suitable for use within a <pre> tag?
On Feb 10, 9:42 am, hy...@lactose.homelinux.net (hymie!) wrote:
> Greetings.
>
> Can somebody recommend to me a perl script or a perl module that
> takes an HTML-formatted <table> and produces a space-formatted
> output that would be suitable for use within a <pre> tag?
This obviously depends on what you content looks like, but the
following is a start.
SCRIPT
#! perl
use strict;
use warnings;
my $content =3D '';
while (<DATA>)
{
next unless /\w/;
chomp;
if ($_ =3D~ m!<(\/?)table!)
{
$content .=3D "<$1pre>
";
next;
}
elsif ($_ =3D~ m!<\/?tr!)
{
$content .=3D "
\n";
next;
}
elsif ($_ =3D~ m!<t[dh]>([^<]*)<\/t[dh]>!)
{
$content .=3D sprintf("%-20s", $1);
next;
}
else
{
warn "ERROR: $_\n";
}
}
print $content;
exit(0);
__DATA__
<table>
<tr>
<td>George</td>
<td>Washington</td>
<td>Virginia</td>
<td>1788</td>
</tr>
<tr>
<td>George</td>
<td>Washington</td>
<td>Virginia</td>
<td>1792</td>
</tr>
<tr>
<td>John</td>
<td>Adams</td>
<td>Massachesetts</td>
<td>1796</td>
</tr>
<tr>
<td>Thomas</td>
<td>Jefferson</td>
<td>Virginia</td>
<td>1800</td>
</tr>
<tr>
<td>Thomas</td>
<td>Jefferson</td>
<td>Virginia</td>
<td>1804</td>
</tr>
</table>
OUTPUT'
<pre>
George Washington Virginia 1788
George Washington Virginia 1792
John Adams Massachesetts 1796
Thomas Jefferson Virginia 1800
Thomas Jefferson Virginia 1804
</pre>
------------------------------
Date: 10 Feb 2011 21:03:01 GMT
From: "WJ" <w_a_x_man@yahoo.com>
Subject: Re: toy list processing problem: collect similar terms
Message-Id: <ij1jq5024t1@enews1.newsguy.com>
Pascal J. Bourguignon wrote:
> Xah Lee <xahlee@gmail.com> writes:
>
>
> > here's a interesting toy list processing problem.
> >
> > I have a list of lists, where each sublist is labelled by
> > a number. I need to collect together the contents of all sublists
> > sharing
> > the same label. So if I have the list
> >
> > ((0 a b) (1 c d) (2 e f) (3 g h) (1 i j) (2 k l) (4 m n) (2 o p) (4
> > q r) (5 s t))
> >
> > where the first element of each sublist is the label, I need to
> > produce:
> >
> > output:
> > ((a b) (c d i j) (e f k l o p) (g h) (m n q r) (s t))
> >
> > a Mathematica solution is here:
> > http://xahlee.org/UnixResource_dir/writ/notations_mma.html
> >
> > R5RS Scheme lisp solution:
> > http://xahlee.org/UnixResource_dir/writ/Sourav_Mukherjee_sourav.work
> > _gmail.scm by Sourav Mukherjee
> >
> > also, a Common Lisp solution can be found here:
> > http://groups.google.com/group/comp.lang.lisp/browse_frm/thread/5d1d
> > ed8824bc750b?
>
> It's too complex. Just write:
>
> (let ((list '((0 a b) (1 c d) (2 e f) (3 g h) (1 i j) (2 k l) (4 m n)
> (2 o p) (4 q r) (5 s t))))
>
> (mapcar (lambda (class) (reduce (function append) class :key
> (function rest)))
> (com.informatimago.common-lisp.list:equivalence-classes list :key
> (function first)))
>
> )
>
> --> ((S T) (Q R M N) (G H) (O P K L E F) (I J C D) (A B))
Clojure:
(def groups '((0 a b)(1 c d)(2 e f)(3 g h)(1 i j)(2 k l)(4 m n)
(2 o p)(4 q r) (5 s t)))
Using group-by:
(map (fn[[k v]](flatten (map rest v))) (group-by first groups))
Using reduce:
(map #(flatten(rest %)) (reduce (fn[h [k & v]]
(merge-with concat h {k v})) {} groups))
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
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Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
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------------------------------
End of Perl-Users Digest V11 Issue 3282
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