accessing array through array reference in hash

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

Given this code:

# a hash holding a reference to the array
my %hash;
print '$aref is ' . $aref ."\n";
$hash{'aref'} = $aref;
print '$hash{\'aref\'} is ' . $hash{'aref'}. "\n";

# get h_ version of array reference
my $h_aref = $hash{'aref'};
print 'array length is ' . scalar(@$h_aref) . "\n";
push @$h_aref, 'value 2';
print 'after 2nd push array length is ' . scalar(@$h_aref) . "\n";
print 'after 2nd push [0] array value is [' . $$h_aref[0] . "]\n";
print 'after push [1] array value is [' . $$h_aref[1] . "]\n";

# now try to access without intermediate $h_aref
#print 'array length is ' . scalar(@$hash{'aref'}) . "\n";   # error
#print 'array length is ' . scalar(@$$hash{'aref'}) . "\n";  # error
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How do I access the array without the intermediate $h_aref?

---------------------------

It is indeed a curly braces thing

my %hash;
print '$aref is ' . $aref ."\n";
$hash{'aref'} = $aref;
print '$hash{\'aref\'} is ' . $hash{'aref'}. "\n";

# get h_ version of array reference
my $h_aref = $hash{'aref'};
print 'array length is ' . scalar(@$h_aref) . "\n";
push @$h_aref, 'value 2';
print 'after 2nd push array length is ' . scalar(@$h_aref) . "\n";
print 'after 2nd push [0] array value is [' . $$h_aref[0] . "]\n";
print 'after 2nd push [1] array value is [' . $$h_aref[1] . "]\n";

# now try to access without intermediate $h_aref
#print 'array length is ' . scalar(@$hash{'aref'}) . "\n";   # error
#print 'array length is ' . scalar(@$$hash{'aref'}) . "\n";  # error
print "now without the intermediate \$h_ref\n"; 
print 'array length is ' . scalar(@{$hash{'aref'}}) . "\n";
push @{$hash{'aref'}}, 'value 3';
print 'array length after 3rd push is ' . scalar(@{$hash{'aref'}}) . "
+\n";
print 'after 3rd push [0] array value is [' . $hash{'aref'}[0] . "]\n"
+;
print 'after 3rd push [1] array value is [' . $hash{'aref'}[1] . "]\n"
+;
print 'after 3rd push [2] array value is [' . $hash{'aref'}[2] . "]\n"
+;
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Thanks to Data::Dumper and References quick reference

Comment on accessing array through array reference in hash Select or Download Code

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Re: accessing array through array reference in hash by ptum (Priest) on Dec 29, 2005 at 00:13 UTC
I think you need curly braces around $hash{'aref'} to explicitly cast it as an array. (Not sure if my terminology is correct.) `#!/usr/local/bin/perl -w use strict; my @array = ('one','two','three'); my $aref = \@array; my %hash = (); $hash{'aref'} = $aref; print "Array length is:", scalar(@{$hash{'aref'}}), " \n";` [download] `Array length is: 3` [download] No good deed goes unpunished. -- (attributed to) Oscar Wilde	[reply] [d/l] [select]
Re^2: accessing array through array reference in hash by phaylon (Curate) on Dec 29, 2005 at 00:27 UTC
Yep, one could try to memorize that @$ dereferences act on the first part of the expression, namely the '$hash' part. If you want to dereference more than the first part, you enclose it in curlies. perldoc perlref knows more about this. Ordinary morality is for ordinary people. -- Aleister Crowley	[reply]
Re: accessing array through array reference in hash by TedPride (Priest) on Dec 29, 2005 at 03:05 UTC
`print "Array length is: ", $#{$hash{'aref'}}+1, "\n"; print "$_\n" for @{$hash{'aref'}};` [download] Or: `print "@{$hash{'aref'}}";` [download]	[reply] [d/l] [select]