Simple Hash Question

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

Hello World:

I have the following code written to generate a hash:

my $count = 1;
my @array = ('A','B','C');
my %hash = ();

for my $i (@array) 
{
  # set key AND initialize by $count as value of key.

  $hash{$i} = $count;      
  $count++;
}
[download]

Now, what I want to do is sort the hash by values and print it out, but my print loop isnt working right. I can get the values out okay, but the keys are not working to print.

Here's what I have.

for my $key ( sort {$hash{$a} <=> $hash{$b} } keys %hash )
{
     print " MIRACLE_HAPPENS is equal to $hash{$key}.<br>\n";
}
[download]

As you can see - it wont print the key name. It'll only print the sorted values. Where it says "MIRACLE HAPPENS" is where I need it to print the key name. Can anyone show me how to do that please?

Thanks!

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Re: Simple Hash Question by kennethk (Abbot) on Nov 18, 2009 at 21:52 UTC
The keys of the hash are what you want to print out. If I understand your difficulty, all you need to do to get your desired result it to use `$key` in place of `$hash{$key}` in your print statement, i.e. `#!/usr/bin/perl use strict; use warnings; my $count = 1; my @array = ('A','B','C'); my %hash = (); for my $i (@array) { # set key AND initialize by $count as value of key. $hash{$i} = $count; $count++; } for my $key ( sort {$hash{$a} <=> $hash{$b} } keys %hash ) { print " MIRACLE_HAPPENS is equal to $key.<br>\n"; }` [download]	[reply] [d/l] [select]
Re: Simple Hash Question by BioLion (Curate) on Nov 18, 2009 at 21:56 UTC
Not sure if I am missing something, but if you want to print the key, print the key: `for my $key ( sort {$hash{$a} <=> $hash{$b} } keys %hash ) { print " MIRACLE_HAPPENS is equal to key : \'$key\' and value : \' +$hash{$key}\'.\n"; }` [download] perldoc may be a good resource for further reading. HTH. Just a something something...	[reply] [d/l]
Re^2: Simple Hash Question by johngg (Canon) on Nov 18, 2009 at 22:44 UTC
A minor point but you don't have to escape single-quotes in a double-quoted string. `$ cat xxx $key = 'abc'; print "Key is: '$key'\n"; $ perl xxx Key is: 'abc' $` [download] I hope this is useful. Cheers, JohnGG	[reply] [d/l]
Re^2: Simple Hash Question by BlenderHead (Novice) on Nov 18, 2009 at 22:19 UTC
Heh... Am sorry guys... Thank you for your help. :) It solved the problem. As per reading the manual - I AM reading the manual... I wouldn't be here if I weren't... ;-)	[reply]
Re: Simple Hash Question by ikegami (Patriarch) on Nov 18, 2009 at 22:12 UTC
If you're trying to count the number of occurrences of each array element, what you want is: `my @array = qw( a b r a c a d a b r a ); my %counts; ++$counts{$_} for @array; for my $key ( sort { {$counts{$b} <=> $counts{$a} } keys %counts ) { print("$key: $counts{$key}\n"); }` [download]	[reply] [d/l]