Declaring and initializing a hash with a list of keys and a list of values

Ever wanted to do:

my @hash{@keys} = @values;
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but of course were stopped by the fact that that's a syntax error? So you resort to either

my %hash; @hash{@keys} = @values;
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my %hash = map { $keys[$_] => $values[$_] } 0..$#keys;
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and that just didn't seem clean? Well, here's another idiom that borders on cool or wacky weird, depending on where you're from!

@$_{@keys} = @values for \my %hash;
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Comment on Declaring and initializing a hash with a list of keys and a list of values Select or Download Code

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Re (tilly) 1: Declaring and initializing a hash with a list of keys and a list of values by tilly (Archbishop) on May 15, 2001 at 21:53 UTC
That depends on fairly subtle scoping semantics. Are you positive that no future Perl will ever localize that hash to the loop? I would be concerned...	[reply]
Re: Re (tilly) 1: Declaring and initializing a hash with a list of keys and a list of values by danger (Priest) on May 15, 2001 at 22:26 UTC
And these 'subtle scoping issues' render the output of Deparse incorrect: `$ perl -MO=Deparse -e '@$_{1,2,3}=(4,5,6) for \my %hash;print keys %ha +sh' foreach $_ (\my(%hash)) { @$_{1, 2, 3} = (4, 5, 6); } print keys %hash; -e syntax OK` [download] Thus, people who try to understand it via the Deparsed version may be somewhat disappointed.	[reply] [d/l]
Re: Re (tilly) 1: Declaring and initializing a hash with a list of keys and a list of values by merlyn (Sage) on May 15, 2001 at 21:55 UTC
No, but it's unlikely to change for Perl5, and all bets are off on Perl6. {grin} -- Randal L. Schwartz, Perl hacker	[reply]
Re: Re (tilly) 1: Declaring and initializing a hash with a list of keys and a list of values by Anonymous Monk on May 15, 2001 at 22:08 UTC
So what? He doesn't access it in the loop. Does it matter if it's localized?	[reply]
Re (tilly) 3: Declaring and initializing a hash with a list of keys and a list of values by tilly (Archbishop) on May 15, 2001 at 22:28 UTC
The purpose of the loop is to initialize a hash that he wants to be available afterwards. If the scoping changes then he has initialized a private hash that disappears before he ever gets a chance to use it. Oops... strict would catch this change.	[reply]
Re: Re (tilly) 3: Declaring and initializing a hash with a list of keys and a list of values by Anonymous Monk on May 15, 2001 at 22:44 UTC
Re (tilly) 5: Declaring and initializing a hash with a list of keys and a list of values by tilly (Archbishop) on May 15, 2001 at 23:27 UTC
Some notes below your chosen depth have not been shown here
(dws)Re: Declaring and initializing a hash with a list of keys and a list of values by dws (Chancellor) on May 15, 2001 at 22:16 UTC
This gets points for being twisted, but it still goes on my "Kids, don't try this before a code review" list. The benefit you get from being able to the the declaration and initialization in one statement is outweighed by the wetware pessimization of making the reader dig to see the `my`.	[reply] [d/l]
Re: (dws)Re: Declaring and initializing a hash with a list of keys and a list of values by merlyn (Sage) on May 15, 2001 at 22:24 UTC
Right. In real code, I'd simply do my first choice in the opening description. However, the idea of declaring a variable and having a reference to it immediately is a fun idiom. I used it earlier in template for using bind_columns with DBI, for example. -- Randal L. Schwartz, Perl hacker	[reply]
Re: Declaring and initializing a hash with a list of keys and a list of values by MeowChow (Vicar) on May 15, 2001 at 21:43 UTC
That's rather pathological. I like it :) MeowChow s aamecha.s a..a\u$&owag.print	[reply]