On Wed, 2013-08-14 at 00:09 +0100, Andrew Beverley wrote:
Hi,
Could someone please explain to me why the following outputs an empty
string rather than *?
[...]
Thanks for all the replies - a very interesting read. I had never even
heard of autovivification, so very useful to know what it
On 14/08/2013 00:09, Andrew Beverley wrote:
Hi,
Could someone please explain to me why the following outputs an empty
string rather than *?
get();
sub get($)
{ my $fields = shift;
my @fields = grep $_ ne 'domain', @$fields;
my $select_fields = $fields ? join(',', map { 'users.' .
On 14/08/2013 00:09, Andrew Beverley wrote:
Could someone please explain to me why the following outputs an empty
string rather than *?
In this case it may be wise to show a “use strict;”, which I assume is
in effect here, otherwise people can just say that @$a on an undefined
$a in the
* Andrew Beverley (a...@andybev.com) [130813 23:24]:
Could someone please explain to me why the following outputs an empty
string rather than *?
get();
sub get($)
{ my $fields = shift;
my @fields = grep $_ ne 'domain', @$fields;
my $select_fields = $fields ? join(',', map {
On Wed, Aug 14, 2013 at 8:40 AM, Mark Overmeer m...@overmeer.net wrote:
* Andrew Beverley (a...@andybev.com) [130813 23:24]:
Could someone please explain to me why the following outputs an empty
string rather than *?
@fields != @$fields, which is causing the confusion.
I don't think the
On 14/08/2013 01:17, Adrian Lai wrote:
The use of @$fields is sufficient to autovivify $fields as an array ref.
Hmmm. Ish.
/In the context of a parameter to grep/ (and even this may be a
misleading condition), the use of @$fields is sufficient to autovivify
$fields as an array ref.
But in
On 14/08/13 08:33, William Blunn wrote:
On 14/08/2013 00:09, Andrew Beverley wrote:
Could someone please explain to me why the following outputs an empty
string rather than *?
In this case it may be wise to show a “use strict;”, which I assume is
in effect here, otherwise people can just say
* Matt Freake (matthew.d.fre...@gmail.com) [130814 08:01]:
On Wed, Aug 14, 2013 at 8:40 AM, Mark Overmeer m...@overmeer.net wrote:
* Andrew Beverley (a...@andybev.com) [130813 23:24]:
Could someone please explain to me why the following outputs an empty
string rather than *?
@fields
On Wed, Aug 14, 2013 at 08:58:05AM +0100, Matt Freake wrote:
On Wed, Aug 14, 2013 at 8:40 AM, Mark Overmeer m...@overmeer.net wrote:
* Andrew Beverley (a...@andybev.com) [130813 23:24]:
Could someone please explain to me why the following outputs an empty
string rather than *?
On 14/08/13 13:12, Abigail wrote:
On Wed, Aug 14, 2013 at 08:58:05AM +0100, Matt Freake wrote:
I don't think the original poster is confusing those two, and when I
applied 'use strict' to the original code (with the sub) it didn't help (no
warnings or errors). The bit I'm stuck on is why does
On 14 August 2013 13:12, Abigail abig...@abigail.be wrote:
My guess: it's an unintentional side-effect of $_ being an alias in the
first argument of grep.
That does appear to be the case, given as other functions don't autovivify.
e.g. perl -E '$y = scalar @$x; say $x if defined $x'
On Wed, Aug 14, 2013 at 1:59 PM, Matt Lawrence matt.lawre...@virgin.net wrote:
man perlglossary:
autovivification
A Graeco-Roman word meaning “to bring oneself to life”. In Perl, storage
locations (lvalues) spontaneously generate themselves as needed, including
the creation of any hard
On Wed, Aug 14, 2013 at 11:26 AM, James Laver james.la...@gmail.com wrote:
perlglossary is wrong. It doesn't only occur as an lvalue but can
occur by access as well.
Yes and no.
autovivification in general applies in writish kinds of context, but
that is a somewhat imprecise concept.
Note
wait, aren't $a and $b special ?
(they magically live for {$a=$b} etc. )
-- vish
On 14 August 2013 04:07, William Blunn bill+london...@blunn.org wrote:
On 14/08/2013 01:17, Adrian Lai wrote:
The use of @$fields is sufficient to autovivify $fields as an array ref.
Hmmm. Ish.
/In the
On Wed, Aug 14, 2013 at 12:35:19PM -0400, Avishalom Shalit wrote:
wait, aren't $a and $b special ?
(they magically live for {$a=$b} etc. )
They are only special in special cases. Outside of that, they are as
friendly as your other variable.
People who pipe up upon seeing some code that uses
On Wed, Aug 14, 2013 at 9:35 AM, Avishalom Shalit avisha...@gmail.com wrote:
wait, aren't $a and $b special ?
(they magically live for {$a=$b} etc. )
IIRC, they're local'ised within the sort block.
You can try it yourself,
$ perl -wle 'print a=$a (pre init); $a = 5; @f = sort {print a=$a
On 08/14/2013 01:03 PM, Abigail wrote:
On Wed, Aug 14, 2013 at 12:35:19PM -0400, Avishalom Shalit wrote:
wait, aren't $a and $b special ?
(they magically live for {$a=$b} etc. )
They are only special in special cases. Outside of that, they are as
friendly as your other variable.
People who
Date: Wed, 14 Aug 2013 19:03:34 +0200
From: abig...@abigail.be
To: london.pm@london.pm.org
Subject: Re: Using grep on undefined array
On Wed, Aug 14, 2013 at 12:35:19PM -0400, Avishalom Shalit wrote:
wait, aren't $a and $b special ?
(they magically live for {$a=$b} etc
On Wed, Aug 14, 2013 at 06:38:04PM +0100, Eduardo Marques wrote:
Date: Wed, 14 Aug 2013 19:03:34 +0200
From: abig...@abigail.be
To: london.pm@london.pm.org
Subject: Re: Using grep on undefined array
On Wed, Aug 14, 2013 at 12:35:19PM -0400, Avishalom Shalit wrote:
wait, aren't
On Wed, Aug 14, 2013 at 01:26:05PM -0400, Uri Guttman wrote:
On 08/14/2013 01:03 PM, Abigail wrote:
On Wed, Aug 14, 2013 at 12:35:19PM -0400, Avishalom Shalit wrote:
wait, aren't $a and $b special ?
(they magically live for {$a=$b} etc. )
They are only special in special cases. Outside of
Hi,
Could someone please explain to me why the following outputs an empty
string rather than *?
get();
sub get($)
{ my $fields = shift;
my @fields = grep $_ ne 'domain', @$fields;
my $select_fields = $fields ? join(',', map { 'users.' . $_ } @fields) :
'*';
print $select_fields\n;
On Tue, Aug 13, 2013 at 4:09 PM, Andrew Beverley a...@andybev.com wrote:
my $select_fields = $fields ? join(',', map { 'users.' . $_ } @fields)
: '*';
my $select_fields = @fields ? join(',', map { 'users.' . $_ } @fields)
: '*';
?
Maybe a lesson in variable naming there ;-)
Paul
On 14 August 2013 00:09, Andrew Beverley a...@andybev.com wrote:
Hi,
Could someone please explain to me why the following outputs an empty
string rather than *?
get();
sub get($)
{ my $fields = shift;
my @fields = grep $_ ne 'domain', @$fields;
my $select_fields = $fields ?
On Aug 13, 2013 7:35 PM, Paul Makepeace pa...@paulm.com wrote:
On Tue, Aug 13, 2013 at 4:09 PM, Andrew Beverley a...@andybev.com wrote:
my $select_fields = $fields ? join(',', map { 'users.' . $_ }
@fields)
: '*';
my $select_fields = @fields ? join(',', map { 'users.' . $_ }
On Tue, Aug 13, 2013 at 4:09 PM, Andrew Beverley a...@andybev.com wrote:
get();
sub get($)
(You probably know this but calling get() like that, i.e. before it's
declared, is denying perl the chance to enforce the subroutine
prototype.)
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