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every combination of Y/N in 5 positions joemacbusiness 03-31-2008
Posted by Gunnar Hjalmarsson on April 2, 2008, 7:21 pm
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 Abigail wrote:
> _
> Gunnar Hjalmarsson (noreply@gunnar.cc) wrote on VCCCXXVIII September
> ^^ Abigail wrote:
> ^^ > David Harmon (source@netcom.com) wrote on VCCCXXVIII September MCMXCIII
> ^^ > [] On Mon, 31 Mar 2008 23:23:25 +0200 in comp.lang.perl.misc, Gunnar
> ^^ > [] >I do, I hope. :)
> ^^ > [] >
> ^^ > [] > foreach my $num ( 0 .. 0b11111 ) {
> ^^ > [] > local *_ = \ sprintf '%05b', $num;
> ^^ > []
> ^^ > [] What is *_ ? It looks like one of those magic perl variables, but
> ^^ > [] I don't find any documentation on it.
> ^^ >
> ^^ > It's a silly attempt to obfuscate the code.
> ^^
> ^^ I didn't do it for the sake of it; please see the sub-thread starting
> ^^ with
> ^^
http://groups.google.com/group/comp.lang.perl.misc/browse_frm/thread/1c6904d6a4774258/e56a5cb3831212df
> ^^ and the advice provided there by Ben and Brian.
>
> I read it. I still think it's obfuscated. Why use a package scoped glob
> if you can use a lexical variable (even $_)?

Pursuing backwards compatibility justifies the obfuscation. The lexical
$_ was news in v5.9.1.

--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl

Posted by Abigail on April 3, 2008, 6:11 am
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 _
Gunnar Hjalmarsson (noreply@gunnar.cc) wrote on VCCCXXVIII September
;; Abigail wrote:
;; > _
;; > Gunnar Hjalmarsson (noreply@gunnar.cc) wrote on VCCCXXVIII September
;; > ^^ Abigail wrote:
;; > ^^ > David Harmon (source@netcom.com) wrote on VCCCXXVIII September MCMXCIII
;; > ^^ > [] On Mon, 31 Mar 2008 23:23:25 +0200 in comp.lang.perl.misc, Gunnar
;; > ^^ > [] >I do, I hope. :)
;; > ^^ > [] >
;; > ^^ > [] > foreach my $num ( 0 .. 0b11111 ) {
;; > ^^ > [] > local *_ = \ sprintf '%05b', $num;
;; > ^^ > []
;; > ^^ > [] What is *_ ? It looks like one of those magic perl variables, but
;; > ^^ > [] I don't find any documentation on it.
;; > ^^ >
;; > ^^ > It's a silly attempt to obfuscate the code.
;; > ^^
;; > ^^ I didn't do it for the sake of it; please see the sub-thread starting
;; > ^^ with
;; > ^^
http://groups.google.com/group/comp.lang.perl.misc/browse_frm/thread/1c6904d6a4774258/e56a5cb3831212df
;; > ^^ and the advice provided there by Ben and Brian.
;; >
;; > I read it. I still think it's obfuscated. Why use a package scoped glob
;; > if you can use a lexical variable (even $_)?
;;
;; Pursuing backwards compatibility justifies the obfuscation. The lexical
;; $_ was news in v5.9.1.



But "my $foo = sprintf ...;" worked since 5.000.


Or do you think '$foo =~ tr /01/YN/' is the obfuscated version of 'tr /01/YN/'?


Abigail
--
perl -wle'print"Κυστ αξοτθες Πεςμ Θαγλες"^"\x80"x24'

Posted by Ben Morrow on April 2, 2008, 8:04 pm
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Quoth abigail@abigail.be:
> _
> Gunnar Hjalmarsson (noreply@gunnar.cc) wrote on VCCCXXVIII September
> ^^ Abigail wrote:
> ^^ > David Harmon (source@netcom.com) wrote on VCCCXXVIII September MCMXCIII
> ^^ > [] On Mon, 31 Mar 2008 23:23:25 +0200 in comp.lang.perl.misc, Gunnar
> ^^ > [] >I do, I hope. :)
> ^^ > [] >
> ^^ > [] > foreach my $num ( 0 .. 0b11111 ) {
> ^^ > [] > local *_ = \ sprintf '%05b', $num;
> ^^ > []
> ^^ > [] What is *_ ? It looks like one of those magic perl variables, but
> ^^ > [] I don't find any documentation on it.
> ^^ >
> ^^ > It's a silly attempt to obfuscate the code.
> ^^
> ^^ I didn't do it for the sake of it; please see the sub-thread starting
> ^^ with
> ^^
>
http://groups.google.com/group/comp.lang.perl.misc/browse_frm/thread/1c6904d6a4774258/e56a5cb3831212df
> ^^ and the advice provided there by Ben and Brian.
>
>
> I read it. I still think it's obfuscated. Why use a package scoped glob
> if you can use a lexical variable (even $_)?

FWIW I entirely agree. For occasions where the convenience of $_ is
useful and 5.10 is not an option, a one-item for loop is a much cleaner
way of safely doing a local assignment than messing around with *_.

Ben

Posted by Gunnar Hjalmarsson on April 2, 2008, 4:20 pm
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David Harmon wrote:
> On Mon, 31 Mar 2008 23:23:25 +0200 in comp.lang.perl.misc, Gunnar
>> I do, I hope. :)
>>
>> foreach my $num ( 0 .. 0b11111 ) {
>> local *_ = \ sprintf '%05b', $num;
>
> What is *_ ? It looks like one of those magic perl variables, but
> I don't find any documentation on it.

Others have told you that it's a typeglob and pointed you to relevant docs.

As regards applicable docs on _the reason_ why I didn't just say

local $_ = sprintf ...

please see the "Localization of globs" section in "perldoc perlsub".

--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl

Posted by David Harmon on April 3, 2008, 2:10 am
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On Wed, 02 Apr 2008 22:20:44 +0200 in comp.lang.perl.misc, Gunnar
>As regards applicable docs on _the reason_ why I didn't just say
>
> local $_ = sprintf ...
>
>please see the "Localization of globs" section in "perldoc perlsub".

What I'm wondering is why you didn't use the much simpler (from my
point of view):

foreach my $num ( 0 .. 0b11111 ) {
my $yn = sprintf '%05b', $num;
$yn =~ tr/01/NY/;
print "$yn\n";
}

Doesn't everybody say to prefer lexical over local, unless you
really need local?

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