On-the-fly hashref

oko1 has asked for the wisdom of the Perl Monks concerning the following question:

My brain does not seem to be working well today; seems like I should be able to do this, but I can't come up with an answer - or even tell if it's possible. I'd appreciate it if the brilliant Monks here could stand in for some of my cerebral capacity... :)

Situation: take a typical hash slice; make an href out of it.

my @data = qw/Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec/;
my %h;
@h{1..12} = @data;
my $x = \%h;
[download]

So far, so good. My question is, given the two lists above, how would you create $x without those other temporary variables? I've been fiddling with things like

# This gets me a hash...
my %x = map { $_ + 1 => (qw/Jan Feb .../)[$_] } 0 .. 11;

# ...but this does not get me a hashref :-\
my $x = \%{ map { $_ + 1 => (qw/Jan Feb .../)[$_] } 0 .. 11 };
[download]

and their ilk for a while, and am not getting it. Help would be appreciated!

[ Oh - and - no, this isn't some critical necessity; it's just me, always trying to learn more about Perl idiom. ]

--
"Language shapes the way we think, and determines what we can think about."
-- B. L. Whorf

Comment on On-the-fly hashref Select or Download Code

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Re: On-the-fly hashref by tirwhan (Abbot) on Sep 28, 2010 at 16:47 UTC
`my $x; @{$x}{1..12}=qw/Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec/;` [download] All dogma is stupid.	[reply] [d/l]
Re: On-the-fly hashref by moritz (Cardinal) on Sep 28, 2010 at 16:52 UTC
`my $x = { map {; $_ + 1 => (qw/Jan Feb Mar/)[$_] } 0 .. 2 }` [download] Perl 6 solution: `my $x = hash <Jan Feb Mar ...> Z 1..12;` [download] You can emulate that in Perl 5 with the zip() function from List::MoreUtils Perl 6 - links to (nearly) everything that is Perl 6.	[reply] [d/l] [select]
Re: On-the-fly hashref by hbm (Hermit) on Sep 28, 2010 at 16:49 UTC
Is this what you want? (Note the curly braces.) `my $x = { map { $_ + 1 => (qw/Jan Feb Mar Apr May/)[$_] } 0..4 }; print map { "$_ => $x->{$_}\n" } keys %$x;` [download]	[reply] [d/l]
Re: On-the-fly hashref by Anonymous Monk on Sep 28, 2010 at 16:50 UTC
References quick reference `## my $x = {}; my $x = { map { $_ + 1 => (qw/Jan Feb .../)[$_] } 0 .. 11 };` [download]	[reply] [d/l]
Re: On-the-fly hashref by jwkrahn (Abbot) on Sep 28, 2010 at 20:08 UTC
`my $x = { qw/ 1 Jan 2 Feb 3 Mar 4 Apr 5 May 6 Jun 7 Jul 8 Aug 9 Sep 10 + Oct 11 Nov 12 Dec / };` [download]	[reply] [d/l]
Re: On-the-fly hashref by BrowserUk (Patriarch) on Sep 28, 2010 at 21:07 UTC
My question is, given the two lists above, how would you create $x without those other temporary variables? Taking you literally that the values (`@data` array already exists, just autovivify the hashref: `my $r; @{ $r }{ 1 .. 12 } = @data;` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. RIP an inspiration; A true Folk's Guy	[reply] [d/l] [select]
Re: On-the-fly hashref by eric256 (Parson) on Sep 28, 2010 at 20:42 UTC
Heres how i would have done it... `my $m = 1; my $hash = { map { $m++ => $_ } qw/Jan Feb Mar Apr May Jun Jul Aug Sep + Oct Nov Dec/ };` [download] ___________ Eric Hodges	[reply] [d/l]
Re: On-the-fly hashref by oko1 (Deacon) on Sep 28, 2010 at 17:10 UTC
Thank you all so much, and ++ to everyone who has responded; I actually managed to remember the hashref constructor (and wrap the 'map' statement in it) while I was waiting for the answers. That's a hour or so that I wasted because my brain refused to give that bit of info up at the right time... I swear, I'd even talked to the bear before posting here, and even that didn't shake it loose. Five minutes of having the question up here in SoPW, and down it came. :) Again, my delighted thanks to everyone - and I'm truly grateful for _all_ the wonderful help you folks provide. An educated sounding board can be the absolutely most helpful thing possible, in the right circumstances! -- "Language shapes the way we think, and determines what we can think about." -- B. L. Whorf	[reply]
Re^2: On-the-fly hashref by muba (Priest) on Sep 29, 2010 at 01:18 UTC
Edit: Never mind, you already did try to translate the problem into your native language (didn't catch the "talk to the bear" part until after I read the article to which you linked, which was after I wrote my reply), so my reply no longer applies... Well, whatever. Read more... (808 Bytes)	[reply]
Re: On-the-fly hashref by ikegami (Patriarch) on Sep 29, 2010 at 05:25 UTC
Why are you using a hash? `my @months = qw/Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec/; ... $months[$month-1] ...` [download]	[reply] [d/l]