Dereference a hash constant

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

Hi,
I have a hash constant like

use constant foo =>{
                        key1 => val1,
                        key2 => val2
                    }
[download]

how I can iterate through the constant foo

while(($key.$val) = each(foo))
{
   print $key{$val};
}
[download]

when I specified key in each , it errors. Do someone know how I can dereference the hash constant foo.

when I print Dumper(foo), I got the folowing

Ref  : HASH$VAR1 = {
          'key1' => val1,
           'key2' => val2
        };
[download]

Thanks,
Tom

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Re: Dereference a hash constant by BrowserUk (Patriarch) on Oct 22, 2009 at 00:32 UTC
Try it this way: `use constant foo => { a .. z };; [0] Perl> print "$k : $v" while ($k,$v) = each %{ foo() };; w : x e : f a : b m : n s : t y : z u : v c : d k : l q : r g : h i : j o : p` [download] Or this: `[0] Perl> print "$k : $v" while ($k,$v) = each %{ +foo };; w : x e : f a : b m : n s : t y : z u : v c : d k : l q : r g : h i : j o : p` [download] The 'trick' is to ensure that `foo` is parsed as a sub not a string or bareword. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. RIP PCW It is as I've been saying!(Audio until 20090817)	[reply] [d/l] [select]
Re^2: Dereference a hash constant by wrinkles (Pilgrim) on Oct 22, 2009 at 06:45 UTC
By the same reasoning: `perl -e 'use constant foo => { a .. z }; print "$k : $v \n" while ($k +,$v) = each %{&foo};'` [download] And this works, but misses the point I guess: `perl -e 'use constant foo => { a..z }; *foo_h=foo; print "$k : $v \n" +while ($k,$v) = each %foo_h;'` [download]	[reply] [d/l] [select]
Re^2: Dereference a hash constant by Anonymous Monk on Oct 22, 2009 at 00:45 UTC
Excellent solution. Thanks!!	[reply]
Re: Dereference a hash constant by bichonfrise74 (Vicar) on Oct 22, 2009 at 00:24 UTC
Hmm... Can you try this? `#!/usr/bin/perl use strict; use constant foo =>{ key1 => 'val1', key2 => 'val2' }; for my $i ( foo ) { for my $j (keys %{$i} ) { print "$j - $i->{$j}\n"; } }` [download]	[reply] [d/l]
Re^2: Dereference a hash constant by Anonymous Monk on Oct 22, 2009 at 00:38 UTC
That works. Thanks much!!	[reply]
Re: Dereference a hash constant by chromatic (Archbishop) on Oct 22, 2009 at 00:22 UTC
I don't believe you can make this work. You're defining `foo` as a hash reference. You'll have to figure out a way to dereference `foo` without making the parser think you're referring to a variable named `%foo` and how to avoid creating a new hash reference on every invocation. (I made a lovely infinite loop this way.) This assumes I even understand what you're trying to do; your example code makes little sense to me. What are you trying to do?	[reply] [d/l] [select]
Re^2: Dereference a hash constant by Anonymous Monk on Oct 22, 2009 at 00:31 UTC
I have a hash which has constant key/values, so I thought of making it as a constant hash. But now I realized it is impossible to iterate through a hash ref. Thanks.	[reply]
Re^3: Dereference a hash constant by BrowserUk (Patriarch) on Oct 22, 2009 at 00:33 UTC
it is impossible to iterate through a hash ref Nuh uh! See 802571. 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 PCW It is as I've been saying!(Audio until 20090817)	[reply]