Finding the size of a nested hash in a HoH

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

Hi! I'm trying to find the size of a nested hash in a HoH. Here i what I've written.

sub ResetHashProteinTally
{

my ($rHoH_ProteinFamilies) = @_; #capturing array

    for my $proteinfamily ( keys %{$rHoH_ProteinFamilies} ) 
    {
    my $size = (keys %{$rHoH_ProteinFamilies->{proteinfamily}});  #---
+-> finds the length of a hash
    print "$size\n";
    }

} #end of sub routine ResetHashProteinTally
[download]

Here is the output I'm getting.

0
0
0
[download]

(There are only 3 nested hashes in the initial data set I'm working with.)

I'm still new to working with HoHes so I've been coming across a couple conceptual problems like this. Thanks in advance.

Comment on Finding the size of a nested hash in a HoH Select or Download Code

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Re: Finding the size of a nested hash in a HoH by moritz (Cardinal) on Nov 10, 2011 at 14:26 UTC
`my $size = (keys %{$rHoH_ProteinFamilies->{proteinfamily}}); ^` [download] You probably meant to write `$proteinfamily` there. Perl 6 - second systems done right	[reply] [d/l] [select]
Re^2: Finding the size of a nested hash in a HoH by Jeri (Scribe) on Nov 10, 2011 at 14:27 UTC
Man. Thanks, (kinda embarrassing)	[reply]
Re: Finding the size of a nested hash in a HoH by mrstlee (Beadle) on Nov 10, 2011 at 16:11 UTC
Maybe using 'each' is a more natural way to go through a hash: `while( my($key, $val) = each %{$rHoH_ProteinFamilies}){ my $size = (keys %{$val->{proteinfamily});` [download] I suppose a more devious method to find the size of a hash is to use the equivalence between arrays and hashes: `my $size = @{[%$val->{proteinfamily}]}/2;` [download] In other words you can think of hashes as arrays sliced up into sequential pairs, p1 & p2, where p1 = the key and p2 = the value. Hence the hash size will always be 1/2 the length of the array representation.	[reply] [d/l] [select]
Re^2: Finding the size of a nested hash in a HoH by BrowserUk (Patriarch) on Nov 10, 2011 at 16:21 UTC
I suppose a more devious method to find the size of a hash Why would you use a "devious method", when `scalar keys %{ $hashref }` gives you it directly, without 1) iterating the entire hash; 2) contructing an array to hold the keys and values of the hash; 3) throwing away all that work and memory having only extracted a count; which you then have to divide by 2 anyway? With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' 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.	[reply] [d/l]
Re^3: Finding the size of a nested hash in a HoH by aaron_baugher (Curate) on Nov 10, 2011 at 16:55 UTC
If `each` were removed from the language, would anyone really miss it? I know it'd break some legacy code, although I doubt I've used it more than once every few years. But is there ever a time when `each` saves more than a line of code over using `keys` and then getting the value in a second step? (Hmm, I'm off to search and see if there's already been a "what's the least useful core function" thread.) Aaron B. My Woefully Neglected Blog, where I occasionally mention Perl.	[reply] [d/l] [select]
Re^4: Finding the size of a nested hash in a HoH by BrowserUk (Patriarch) on Nov 10, 2011 at 17:16 UTC
Re^5: Finding the size of a nested hash in a HoH by remiah (Hermit) on Nov 11, 2011 at 07:51 UTC
Some notes below your chosen depth have not been shown here
Re^5: Finding the size of a nested hash in a HoH by aaron_baugher (Curate) on Nov 11, 2011 at 14:59 UTC


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