[30218] in Perl-Users-Digest
Perl-Users Digest, Issue: 1461 Volume: 11
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Tue Apr 22 16:43:00 2008
Date: Tue, 22 Apr 2008 13:42:27 -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, 22 Apr 2008 Volume: 11 Number: 1461
Today's topics:
Perl - delayed evaluation of variables? <wardct@gmail.com>
Re: Perl - delayed evaluation of variables? <smallpond@juno.com>
Re: Perl - delayed evaluation of variables? <smallpond@juno.com>
Re: Perl - delayed evaluation of variables? <ben@morrow.me.uk>
Re: Perl - delayed evaluation of variables? <noreply@gunnar.cc>
Re: Perl - delayed evaluation of variables? <syscjm@sumire.gwu.edu>
Re: Perl - delayed evaluation of variables? <wardct@gmail.com>
Re: Perl - delayed evaluation of variables? <wardct@gmail.com>
Re: Perl - delayed evaluation of variables? <skye.shaw@gmail.com>
Perl LWP Issue with JSP's <mark1.thompson45@btinternet.com>
Re: Perl LWP Issue with JSP's <mark1.thompson45@btinternet.com>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Thu, 17 Apr 2008 03:56:27 -0700 (PDT)
From: ditman <wardct@gmail.com>
Subject: Perl - delayed evaluation of variables?
Message-Id: <6dcacaaa-9c5d-4466-84e4-35d8850bc685@m44g2000hsc.googlegroups.com>
Hi,
I have a script where I define a string at the top of the file.
The string includes a variable which is not set until later in the
script. As a result the variable is evaluated as null and does not
appear in the string.
Is there a way to say to the Perl interpreter - do not evaluate the
string defined at the start, but wait until it is used?
Code sample:
my $LANG_LOCALE; # defined, but null value
my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
not found at $_TOP/services/imApp/$LANG_LOCALE";
function show_message(){
$LANG_LOCALE = "de-DE";
print "$ERROR_MSG_BUILDVER_INI_MISSING";
}
------------------------------
Date: Thu, 17 Apr 2008 05:00:15 -0700 (PDT)
From: smallpond <smallpond@juno.com>
Subject: Re: Perl - delayed evaluation of variables?
Message-Id: <3ccbb935-5b0c-4085-a91c-0b198c5dc71f@l64g2000hse.googlegroups.com>
On Apr 17, 6:56 am, ditman <war...@gmail.com> wrote:
> Hi,
>
> I have a script where I define a string at the top of the file.
> The string includes a variable which is not set until later in the
> script. As a result the variable is evaluated as null and does not
> appear in the string.
> Is there a way to say to the Perl interpreter - do not evaluate the
> string defined at the start, but wait until it is used?
>
> Code sample:
>
> my $LANG_LOCALE; # defined, but null value
>
> my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
> not found at $_TOP/services/imApp/$LANG_LOCALE";
>
> function show_message(){
> $LANG_LOCALE = "de-DE";
> print "$ERROR_MSG_BUILDVER_INI_MISSING";
>
> }
To do your function, just remove the quotes
so the variable is evaluated inside the function:
function show_message(){
$LANG_LOCALE = "de-DE";
print $ERROR_MSG_BUILDVER_INI_MISSING;
}
To answer your more general question, there is
no such thing as "defining" a string. You were
making an assignment, which does the evaluation
of the expression. If you really want to evaluate
an expression later, look at the eval function.
--S
------------------------------
Date: Thu, 17 Apr 2008 05:04:26 -0700 (PDT)
From: smallpond <smallpond@juno.com>
Subject: Re: Perl - delayed evaluation of variables?
Message-Id: <495f3659-1691-464f-a3ba-2e1c8b4bdc30@c65g2000hsa.googlegroups.com>
On Apr 17, 8:00 am, smallpond <smallp...@juno.com> wrote:
> On Apr 17, 6:56 am, ditman <war...@gmail.com> wrote:
>
>
>
> > Hi,
>
> > I have a script where I define a string at the top of the file.
> > The string includes a variable which is not set until later in the
> > script. As a result the variable is evaluated as null and does not
> > appear in the string.
> > Is there a way to say to the Perl interpreter - do not evaluate the
> > string defined at the start, but wait until it is used?
>
> > Code sample:
>
> > my $LANG_LOCALE; # defined, but null value
>
> > my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
> > not found at $_TOP/services/imApp/$LANG_LOCALE";
>
> > function show_message(){
> > $LANG_LOCALE = "de-DE";
> > print "$ERROR_MSG_BUILDVER_INI_MISSING";
>
> > }
>
> To do your function, just remove the quotes
> so the variable is evaluated inside the function:
>
> function show_message(){
> $LANG_LOCALE = "de-DE";
> print $ERROR_MSG_BUILDVER_INI_MISSING;
>
> }
>
> To answer your more general question, there is
> no such thing as "defining" a string. You were
> making an assignment, which does the evaluation
> of the expression. If you really want to evaluate
> an expression later, look at the eval function.
> --S
Sorry. Meant to move the expression inside the
function, of course, not just the variable.
------------------------------
Date: Thu, 17 Apr 2008 13:26:37 +0100
From: Ben Morrow <ben@morrow.me.uk>
Subject: Re: Perl - delayed evaluation of variables?
Message-Id: <t8sjd5-qki.ln1@osiris.mauzo.dyndns.org>
Quoth ditman <wardct@gmail.com>:
>
> I have a script where I define a string at the top of the file.
> The string includes a variable which is not set until later in the
> script. As a result the variable is evaluated as null and does not
> appear in the string.
> Is there a way to say to the Perl interpreter - do not evaluate the
> string defined at the start, but wait until it is used?
>
> Code sample:
>
> my $LANG_LOCALE; # defined, but null value
>
> my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
> not found at $_TOP/services/imApp/$LANG_LOCALE";
>
> function show_message(){
> $LANG_LOCALE = "de-DE";
> print "$ERROR_MSG_BUILDVER_INI_MISSING";
> }
You can use Scalar::Defer for this. Note that all variables used
(whether lexical or global) will need to be declared first.
#!/usr/bin/perl
use strict;
use warnings;
use Scalar::Defer qw/lazy/;
my $LANG_LOCALE;
our $_TOP;
# This can be as complicated an expression as you like, including
# multiple statements.
my $MSG = lazy { "Not found at $_TOP/services/imApp/$LANG_LOCALE" };
$LANG_LOCALE = 'en_GB';
$_TOP = '/foo/bar';
print $MSG;
This will only evaluate the interpolation once, then cache the result;
if you want it re-evaluated every time, use 'defer' instead of 'lazy'.
Ben
------------------------------
Date: Thu, 17 Apr 2008 16:45:35 +0200
From: Gunnar Hjalmarsson <noreply@gunnar.cc>
Subject: Re: Perl - delayed evaluation of variables?
Message-Id: <66p63oF2l3136U1@mid.individual.net>
ditman wrote:
> I have a script where I define a string at the top of the file.
> The string includes a variable which is not set until later in the
> script. As a result the variable is evaluated as null and does not
> appear in the string.
> Is there a way to say to the Perl interpreter - do not evaluate the
> string defined at the start, but wait until it is used?
>
> Code sample:
>
> my $LANG_LOCALE; # defined, but null value
>
> my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
> not found at $_TOP/services/imApp/$LANG_LOCALE";
>
> function show_message(){
> $LANG_LOCALE = "de-DE";
> print "$ERROR_MSG_BUILDVER_INI_MISSING";
> }
Why don't you simply pass the variables to the function?
sub show_message {
my ($top, $lang) = @_;
print 'BuildVer.ini file for service not' .
" found at $top/services/imApp/$lang";
}
show_message( $_TOP, $LANG_LOCALE );
--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl
------------------------------
Date: Thu, 17 Apr 2008 09:46:22 -0500
From: Chris Mattern <syscjm@sumire.gwu.edu>
Subject: Re: Perl - delayed evaluation of variables?
Message-Id: <slrng0eolu.drd.syscjm@sumire.gwu.edu>
On 2008-04-17, ditman <wardct@gmail.com> wrote:
> Hi,
>
> I have a script where I define a string at the top of the file.
> The string includes a variable which is not set until later in the
> script. As a result the variable is evaluated as null and does not
> appear in the string.
> Is there a way to say to the Perl interpreter - do not evaluate the
> string defined at the start, but wait until it is used?
Sure. Define the string when it is used.
>
> Code sample:
>
> my $LANG_LOCALE; # defined, but null value
>
> my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
> not found at $_TOP/services/imApp/$LANG_LOCALE";
>
> function show_message(){
> $LANG_LOCALE = "de-DE";
> print "$ERROR_MSG_BUILDVER_INI_MISSING";
> }
Is there a reason you are not defining $LANG_LOCALE until show_message?
How are you attempting to find BuildVer.ini when you don't know where
$LANG_LOCALE is until you call the function that tells you you can't
find BuildVer.ini in a directory defined by $LANG_LOCALE?
--
Christopher Mattern
NOTICE
Thank you for noticing this new notice
Your noticing it has been noted
And will be reported to the authorities
------------------------------
Date: Thu, 17 Apr 2008 08:23:36 -0700 (PDT)
From: technut666 <wardct@gmail.com>
Subject: Re: Perl - delayed evaluation of variables?
Message-Id: <ae761e48-8a39-46ba-a884-800334dbe3df@l42g2000hsc.googlegroups.com>
On Apr 17, 1:04 pm, smallpond <smallp...@juno.com> wrote:
> On Apr 17, 8:00 am, smallpond <smallp...@juno.com> wrote:
>
>
>
> > On Apr 17, 6:56 am, ditman <war...@gmail.com> wrote:
>
> > > Hi,
>
> > > I have a script where I define a string at the top of the file.
> > > The string includes a variable which is not set until later in the
> > > script. As a result the variable is evaluated as null and does not
> > > appear in the string.
> > > Is there a way to say to the Perl interpreter - do not evaluate the
> > > string defined at the start, but wait until it is used?
>
> > > Code sample:
>
> > > my $LANG_LOCALE; # defined, but null value
>
> > > my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
> > > not found at $_TOP/services/imApp/$LANG_LOCALE";
>
> > > function show_message(){
> > > $LANG_LOCALE = "de-DE";
> > > print "$ERROR_MSG_BUILDVER_INI_MISSING";
>
> > > }
>
> > To do your function, just remove the quotes
> > so the variable is evaluated inside the function:
>
> > function show_message(){
> > $LANG_LOCALE = "de-DE";
> > print $ERROR_MSG_BUILDVER_INI_MISSING;
>
> > }
>
> > To answer your more general question, there is
> > no such thing as "defining" a string. You were
> > making an assignment, which does the evaluation
> > of the expression. If you really want to evaluate
> > an expression later, look at the eval function.
> > --S
>
> Sorry. Meant to move the expression inside the
> function, of course, not just the variable.
Hi,
Thanks for you response! :D
The code sample was to just illustrate the issue - there is more going
on here.
Basically I have to declare a bunch of error messages at the start of
the script.
I then read in a file with a bunch of environment settings - one of
which is $lang_locale. So I can't know $lang_locale until after I
have declared the error messages. (Again a simplified description of
what is going on in the script :D )
------------------------------
Date: Thu, 17 Apr 2008 08:40:52 -0700 (PDT)
From: technut666 <wardct@gmail.com>
Subject: Re: Perl - delayed evaluation of variables?
Message-Id: <88b6d9b0-ff87-48c6-8cbd-65cccfefc929@b64g2000hsa.googlegroups.com>
On Apr 17, 3:46 pm, Chris Mattern <sys...@sumire.gwu.edu> wrote:
> On 2008-04-17, ditman <war...@gmail.com> wrote:
>
> > Hi,
>
> > I have a script where I define a string at the top of the file.
> > The string includes a variable which is not set until later in the
> > script. As a result the variable is evaluated as null and does not
> > appear in the string.
> > Is there a way to say to the Perl interpreter - do not evaluate the
> > string defined at the start, but wait until it is used?
>
> Sure. Define the string when it is used.
>
>
>
> > Code sample:
>
> > my $LANG_LOCALE; # defined, but null value
>
> > my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
> > not found at $_TOP/services/imApp/$LANG_LOCALE";
>
> > function show_message(){
> > $LANG_LOCALE = "de-DE";
> > print "$ERROR_MSG_BUILDVER_INI_MISSING";
> > }
>
> Is there a reason you are not defining $LANG_LOCALE until show_message?
> How are you attempting to find BuildVer.ini when you don't know where
> $LANG_LOCALE is until you call the function that tells you you can't
> find BuildVer.ini in a directory defined by $LANG_LOCALE?
>
> --
> Christopher Mattern
>
> NOTICE
> Thank you for noticing this new notice
> Your noticing it has been noted
> And will be reported to the authorities
Hi,
Thanks to everyone for your responses.
I am defining a bunch of error messages at the start of the script.
Then I read in a bunch of environment settings from an external file,
one of which is $LANG_LOCALE. So I can't know $LANG_LOCALE before I
declare the error message.
Fortunately I have found a solution in the Perl Cookbook of all
places! :D
It's not a delayed expansion, but it does what I need.
Goes something like this:
my $LANG_LOCALE; # defined, but null value
my $ERROR_MSG_BUILDVER_INI_MISSING = "BuildVer.ini file for service
not found at $_TOP/services/imApp/\$LANG_LOCALE";
function show_message(){
$LANG_LOCALE = "de-DE";
$ERROR_MSG_BUILDVER_INI_MISSING =~ s/(\$\w+)/$1/eeg;
print "$ERROR_MSG_BUILDVER_INI_MISSING";
}
Description:
Using the backslash before $LANG_LOCALE in the
$ERROR_MSG_BUILDVER_INI_MISSING string means it is not evaluated.
Then in the function, the regexp looks for anything which looks like a
variable (a dollar sign plus text).
This is captured as $1.
The 'ee' means "Evaluate the right side as a string then eval the
result". So if $1 is the string $LANG_LOCALE and $LANG_LOCALE="de-
DE", this is evaluated as "de-DE".
And the 'g' means operate globally obviously - so this will work for
all variables.
Hope this is clearly explained.
Regards,
C.
------------------------------
Date: Fri, 18 Apr 2008 00:38:25 -0700 (PDT)
From: "Skye Shaw!@#$" <skye.shaw@gmail.com>
Subject: Re: Perl - delayed evaluation of variables?
Message-Id: <8f4f190b-a616-483e-8ed4-cb66b0b22324@c58g2000hsc.googlegroups.com>
On Apr 17, 3:56=A0am, ditman <war...@gmail.com> wrote:
> Hi,
>
> I have a script where I define a string at the top of the file.
> The string includes a variable which is not set until later in the
> script. =A0As a result the variable is evaluated as null and does not
> appear in the string.
> Is there a way to say to the Perl interpreter - do not evaluate the
> string defined at the start, but wait until it is used?
Yikes
> Code sample:
>
> my $LANG_LOCALE; # defined, but null value
>
> my $ERROR_MSG_BUILDVER_INI_MISSING =3D "BuildVer.ini file for service
> not found at $_TOP/services/imApp/$LANG_LOCALE";
>
> function show_message(){
> =A0 $LANG_LOCALE =3D "de-DE";
> =A0 print "$ERROR_MSG_BUILDVER_INI_MISSING";
>
> }
If you must:
my $LANG_LOCALE; # defined, but null value
my $ERROR_MSG_BUILDVER_INI_MISSING =3D 'print "BuildVer.ini file for
service
not found at $_TOP/services/imApp/$LANG_LOCALE"';
sub show_message {
$LANG_LOCALE =3D "de-DE";
eval $ERROR_MSG_BUILDVER_INI_MISSING";
}
If you really want to go the template route my not use printf?
my $ERROR_XYZ =3D 'Damn it Jim, I'm a %s not a %s';
printf $ERROR_XYZ, 'Aussie', 'Kiwi';
-Skye
------------------------------
Date: Wed, 16 Apr 2008 11:29:04 -0700 (PDT)
From: tommo_blade <mark1.thompson45@btinternet.com>
Subject: Perl LWP Issue with JSP's
Message-Id: <f5b1a411-095d-45d0-94be-d26cf3f10cbe@m73g2000hsh.googlegroups.com>
Hi, I am tring to retrieve some data from a source page and following
that a link within that source page, I am able to get the data from
the source page OK and also extract the link from the source page but
when I try to get the data from that link I get an error, I get most
of the data from the link but the error appears to be something to do
with a JSP but not sure, can anyone help, the snippet of code below is
what I am using to get the data from the link and the info below that
is the error I get.
p.s. if I do a "view source" on the page I can see the data I need so
I would have thought that the LWP call would have retrieved it.
$ua = LWP::UserAgent->new();
$ua->cookie_jar($cookie_jar);
$req = new HTTP::Request GET => $url;
$res = $ua->request($req);
<!-- clientplayerinfo-football.jsp starts -->
Failure trying to include /clientplayerinfo-football-new.jsp:
Exception in JSP: /clientplayerinfo-football-new.jsp:118
115: <td rowspan="3" width="2"></td>
116: <td align="center" valign="middle">
117: <table width="530"
height="36" border="0" cellpadding="0" cellspacing="0" align="center">
118: <ctv:sort var="facts"
items="${player.facts}" property="gameFixture.date" ascending="false" /
>
119: <c:set var="playerScore"
value="0" />
120: <c:set var="uniqueRules"
value="${player.game.uniqueRules}" />
121: <tr align="left" valign="top">
Stacktrace:
<!-- clientplayerinfo-football.jsp ends -->
------------------------------
Date: Wed, 16 Apr 2008 12:00:19 -0700 (PDT)
From: tommo_blade <mark1.thompson45@btinternet.com>
Subject: Re: Perl LWP Issue with JSP's
Message-Id: <c05f55bf-d3ba-42d3-b951-8cdcff101629@e67g2000hsa.googlegroups.com>
Sorry, it was a typo - all working ok now...
------------------------------
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 V11 Issue 1461
***************************************
