[26156] in Perl-Users-Digest
Perl-Users Digest, Issue: 8347 Volume: 10
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Mon Aug 22 18:05:23 2005
Date: Mon, 22 Aug 2005 15:05:05 -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 Mon, 22 Aug 2005 Volume: 10 Number: 8347
Today's topics:
Dereferencing array/hash element with @{ } instead of $ (Hue-Bond)
Re: Use of uninitialized value Error <tadmc@augustmail.com>
Re: Use of uninitialized value Error <nospam@nospam.com>
Re: Use of uninitialized value Error <nospam@nospam.com>
Use of uninitialized value in substitution (s///) <hlawson@triad.rr.com>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Mon, 22 Aug 2005 21:07:47 +0000 (UTC)
From: "David Serrano (Hue-Bond)" <responder_solo_en_el_grupo@yahoo.es>
Subject: Dereferencing array/hash element with @{ } instead of ${ }
Message-Id: <slrndgkfl3.1qi.responder_solo_en_el_grupo@genus.hue-bond.info>
I'm learning to use references and complex data structures. No problem at
all until I discovered a typo in a program that was working perfectly. I've
investigated that (reading perlref, perldsc, perldata and perlobj) but found
nothing similar except pseudo-hashes, but I think this is not the case since
I'm under strict and I'm not setting up a special first field.
This is the (conveniently shortened) code:
use strict;
use warnings;
my $lines = [
{
stations => [
{
name => "baz"
}
]
}
];
# same as $lines->[0]{stations}[0]{name}
print ${ ${ ${ $lines->[0] }{stations} }[0] }{name},"\n";
print ${ ${ $lines->[0] }{stations} }[0] ,"\n";
print @{ ${ $lines->[0] }{stations} }[0] ,"\n";
print ${ $lines->[0] }{stations} ,"\n";
print @{ $lines->[0] }{stations} ,"\n";
And the output:
baz
HASH(0x8071fbc)
HASH(0x8071fbc)
ARRAY(0x8071fec)
ARRAY(0x8071fec)
I expect to see some error instead of the second HASH(0x8071fbc) and the
second ARRAY(0x8071fec). Why not?
[ ... ] Could it be a slice of just one element?
use strict;
use warnings;
my $a=[4,6,8];
print $$a[1], "\n"; ## normal usage, prints 6 without warnings
print @$a[1], "\n"; ## what I'm doing, also prints 6 without warnings
Using an array instead of a reference yields "Scalar value @a[1] better
written as $a[1] at - line 4.", why doesn't that happen with references?
Maybe Perl doesn't know what @$a[1] is?
--
David Serrano
------------------------------
Date: Mon, 22 Aug 2005 15:52:02 -0500
From: Tad McClellan <tadmc@augustmail.com>
Subject: Re: Use of uninitialized value Error
Message-Id: <slrndgkeni.m06.tadmc@magna.augustmail.com>
A. Sinan Unur <1usa@llenroc.ude.invalid> wrote:
> "daniel kaplan" <nospam@nospam.com> wrote in
> news:1124660477.785784@nntp.acecape.com:
>
>> The error is: uninittest.pl: Use of uninitialized value in
>> concatenation (.) or string at uninittest.pl line 45.
> To fix your code, you need to make sure all variables hold valid values
> when you use them in operations.
Your answer is not in keeping with "one of the rudest people i have
ever encountered on a newsgroup".
You're going to blow your reputation! :-)
--
Tad McClellan SGML consulting
tadmc@augustmail.com Perl programming
Fort Worth, Texas
------------------------------
Date: Mon, 22 Aug 2005 17:04:36 -0400
From: "daniel kaplan" <nospam@nospam.com>
Subject: Re: Use of uninitialized value Error
Message-Id: <1124744604.232839@nntp.acecape.com>
"Tad McClellan" <tadmc@augustmail.com> wrote in message
news:slrndgkeni.m06.tadmc@magna.augustmail.com...
> Your answer is not in keeping with "one of the rudest people i have
> ever encountered on a newsgroup".
>
> You're going to blow your reputation! :-)
oy...here we go again ;-)
------------------------------
Date: Mon, 22 Aug 2005 17:07:18 -0400
From: "daniel kaplan" <nospam@nospam.com>
Subject: Re: Use of uninitialized value Error
Message-Id: <1124744766.460026@nntp.acecape.com>
"Tad McClellan" <tadmc@augustmail.com> wrote in message
news:slrndgkeni.m06.tadmc@magna.augustmail.com...
> Your answer is not in keeping with "one of the rudest people i have
> ever encountered on a newsgroup".
>
> You're going to blow your reputation! :-)
ah but don't worry, i fought back a little ...
in reply to:
>> my $came_from = 'I must learn proper CGI programming first';
i responded with:
But even after changing: my $came_from = xxxxxxxxx
to: my $came_from = 'You need to learn to be nicer to others';
so if you want, we can do this dance....but am so tired, we don't have to,
do we? ;-)
daniel
------------------------------
Date: Mon, 22 Aug 2005 21:51:37 GMT
From: Hugh Lawson <hlawson@triad.rr.com>
Subject: Use of uninitialized value in substitution (s///)
Message-Id: <87y86tk5cm.fsf@desktop.xx.yy>
This error occurs in this program. What is uninitialized in the substitution?
I've spent quite a while searching for clues.
#! /usr/bin/perl
use strict;
use warnings;
use diagnostics;
use GDBM_File;
my $db_file;
my %fred;
my $word;
my $defn;
my $db;
$db_file="frenchwords";
$db = tie %fred, 'GDBM_File', $db_file, &GDBM_WRCREAT, 0640;
# Install DBM Filters.
######Error comes on next line******************
$db->filter_fetch_key ( sub { s/\0$// } ) ;
$db->filter_store_key ( sub { $_ .= "\0" } ) ;
$db->filter_fetch_value( sub { s/\0$// } ) ;
$db->filter_store_value( sub { $_ .= "\0" } ) ;
while (($word, $defn) = each (%fred)) { print ("$word: $defn\n"); }
undef $db;
untie %fred;
#end of program.
--
Hugh Lawson
hlawson@triad.rr.com
------------------------------
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 8347
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