[26399] in Perl-Users-Digest
Perl-Users Digest, Issue: 8570 Volume: 10
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Wed Oct 26 03:05:25 2005
Date: Wed, 26 Oct 2005 00:05:06 -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 Wed, 26 Oct 2005 Volume: 10 Number: 8570
Today's topics:
FAQ 7.15 How do I create a static variable? <comdog@pair.com>
Re: getElementsByTagName, tag does not exist robic0@yahoo.com
How to detect memory usage in hash? <sonet.all@msa.hinet.net>
Re: How to detect memory usage in hash? <nobody@bigpond.com>
Re: Moving data structure around better than globals? <tadmc@augustmail.com>
Timelocal input, post good Date filters (from - to) robic0@yahoo.com
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Wed, 26 Oct 2005 04:03:01 +0000 (UTC)
From: PerlFAQ Server <comdog@pair.com>
Subject: FAQ 7.15 How do I create a static variable?
Message-Id: <djmv5l$p93$1@reader2.panix.com>
This message is one of several periodic postings to comp.lang.perl.misc
intended to make it easier for perl programmers to find answers to
common questions. The core of this message represents an excerpt
from the documentation provided with Perl.
--------------------------------------------------------------------
7.15: How do I create a static variable?
(contributed by brian d foy)
Perl doesn't have "static" variables, which can only be accessed from
the function in which they are declared. You can get the same effect
with lexical variables, though.
You can fake a static variable by using a lexical variable which goes of
scope. In this example, you define the subroutine "counter", and it uses
the lexical variable $count. Since you wrap this in a BEGIN block,
$count is defined at compile-time, but also goes out of scope at the end
of the BEGIN block. The BEGIN block also ensures that the subroutine and
the value it uses is defined at compile-time so the subroutine is ready
to use just like any other subroutine, and you can put this code in the
same place as other subroutines in the program text (i.e. at the end of
the code, typically). The subroutine "counter" still has a reference to
the data, and is the only way you can access the value (and each time
you do, you increment the value). The data in chunk of memory defined by
$count is private to "counter".
BEGIN {
my $count = 1;
sub counter { $count++ }
}
my $start = count();
.... # code that calls count();
my $end = count();
In the previous example, you created a function-private variable because
only one function remembered its reference. You could define multiple
functions while the variable is in scope, and each function can share
the "private" variable. It's not really "static" because you can access
it outside the function while the lexical variable is in scope, and even
create references to it. In this example, "increment_count" and
"return_count" share the variable. One function adds to the value and
the other simply returns the value. They can both access $count, and
since it has gone out of scope, there is no other way to access it.
BEGIN {
my $count = 1;
sub increment_count { $count++ }
sub return_count { $count }
}
To declare a file-private variable, you still use a lexical variable. A
file is also a scope, so a lexical variable defined in the file cannot
be seen from any other file.
See "Persistent Private Variables" in perlsub for more information. The
discussion of closures in perlref may help you even though we did not
use anonymous subroutines in this answer. See "Persistent Private
Variables" in perlsub for details.
--------------------------------------------------------------------
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The perlfaq manual page contains the following copyright notice.
AUTHOR AND COPYRIGHT
Copyright (c) 1997-2002 Tom Christiansen and Nathan
Torkington, and other contributors as noted. All rights
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This posting is provided in the hope that it will be useful but
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------------------------------
Date: Tue, 25 Oct 2005 22:31:17 -0700
From: robic0@yahoo.com
Subject: Re: getElementsByTagName, tag does not exist
Message-Id: <jr4ul15rtli2rsnnfg3k3lgddnm4uu0r4f@4ax.com>
On Sun, 23 Oct 2005 15:04:54 -0700, robic0@yahoo.com wrote:
Actually, DOM is exponentionaly irrelavent in modern xml parsing.
Its use is fadinding like an old 59 Buick in 1965.
>On Sat, 22 Oct 2005 09:57:21 -0400, "Matt Garrish"
><matthew.garrish@sympatico.ca> wrote:
>Your right Matt. I sometimes make those comments on
>Friday nights after the pub. Dissregard those,
>and sorry for them. But I am usually coherent on here
>and am interrested in technical development.
>I mean no harm. - thanks!
>>
>><robic0@yahoo.com> wrote in message
>>news:e5ojl1hdas8utf88tt1mknpsullko6gi29@4ax.com...
>>> On Thu, 20 Oct 2005 08:04:45 -0400, "Matt Garrish"
>>> <matthew.garrish@sympatico.ca> wrote:
>>>>Simplistic statements like sax for everything aren't helpful.
>>>
>>> I didn't getcha on this statement..
>>>
>>
>>You only talk about DOM and SAX in your original post (and being the two
>>most common and supported parsers, that's not surprising). By following up
>>and saying you'll never use nodes again you're implying that SAX is the only
>>way to go. That's all that was meant.
>>
>>Matt
>>
------------------------------
Date: Wed, 26 Oct 2005 11:23:19 +0800
From: "sonet" <sonet.all@msa.hinet.net>
Subject: How to detect memory usage in hash?
Message-Id: <djmssr$muv$1@netnews.hinet.net>
How to know how many memory usage in a hash??
I just can use top to see the memory usage?
-----How to rough estimate ?---
my %hash;
for (my $i=0;$i<=10000;$i++){
$hash{abc}{$i}='testing';
}
------------------------------
Date: Wed, 26 Oct 2005 04:01:55 GMT
From: Gregory Toomey <nobody@bigpond.com>
Subject: Re: How to detect memory usage in hash?
Message-Id: <435effb2@news.comindico.com.au>
sonet wrote:
> How to know how many memory usage in a hash??
> I just can use top to see the memory usage?
>
> -----How to rough estimate ?---
>
> my %hash;
> for (my $i=0;$i<=10000;$i++){
> $hash{abc}{$i}='testing';
> }
For a non-portable linux solution, read /proc/$$/status, and look for a line
with 'VmSize'.
gtoomey
------------------------------
Date: Tue, 25 Oct 2005 21:01:00 -0500
From: Tad McClellan <tadmc@augustmail.com>
Subject: Re: Moving data structure around better than globals?
Message-Id: <slrndltoqs.hcj.tadmc@magna.augustmail.com>
Gunnar Hjalmarsson <noreply@gunnar.cc> wrote:
> I have accepted that package globals as well as file scoped lexicals
> should be avoided if possible,
I'd say "if practicable" rather than "if possible".
It is the _abuse_ of global variables that is often warned against,
they do have their place.
My personal red flag is when there are "many" (over 10?) globals.
When I see that developing, I recast them to a single global hash.
> $d->{param} - hash ref to CGI parameters
> $d->{user} - hash ref to certain data about the current user,
> grabbed at authentication
> $d->{error} - array ref to alerts to be displayed on screen
>
> I'm passing $d around to just about all the functions,
So then, it would hit my "impracticable" limit. :-)
> and it struck me
> that this approach actually is very similar to using global variables.
I very often have a single global hash with "configuration"
type values in it.
> So my question is: Why would this be better (if you think it is)?
I wouldn't say that passing the same arg in every function call
is better.
Judicious use of globals is good practice (it's just that the most
common uses are not judicious, so a knee-jerk "don't use globals"
is more often right than it is wrong).
--
Tad McClellan SGML consulting
tadmc@augustmail.com Perl programming
Fort Worth, Texas
------------------------------
Date: Tue, 25 Oct 2005 21:46:32 -0700
From: robic0@yahoo.com
Subject: Timelocal input, post good Date filters (from - to)
Message-Id: <t72ul1htar3krqf6aiflt9mr96ive71kbn@4ax.com>
I get some weird concat warnings on print if enabled so its commented.
Post any you have (or make some up).
Here's mine ..
use strict;
#use warnings;
my @dates = ('2/30/5-7/2005', '2/5', '-3/29.2000', '4-12/05',
'-12/01-1/03', '10/2002,8/31/2005', '1/2-asdvf');
for (@dates) {
my $date = $_;
print '-'x40,"\n$date\n";
$date =~ /.*/;
$date =~
/^(?:\/*)([0-9]+)?(?:\/*)([0-9]+)?(?:\/*)([0-9]+)?(?:\/*)([,-]*)(?:\/*)([0-9]+)?(?:\/*)([0-9]+)?(?:\/*)([0-9]+)?(?:\/*)$/;
print "date = ($1)($2)($3)($4)($5)($6)($7)\n";
}
__DATA__
----------------------------------------
2/30/5-7/2005
date = (2)(30)(5)(-)(7)(2005)()
----------------------------------------
2/5
date = (2)(5)()()()()()
----------------------------------------
-3/29.2000
date = ()()()()()()()
----------------------------------------
4-12/05
date = (4)()()(-)(12)(05)()
----------------------------------------
-12/01-1/03
date = ()()()()()()()
----------------------------------------
10/2002,8/31/2005
date = (10)(2002)()(,)(8)(31)(2005)
----------------------------------------
1/2-asdvf
date = ()()()()()()()
------------------------------
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)
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------------------------------
End of Perl-Users Digest V10 Issue 8570
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