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push

Posted on 2009-05-07
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Last Modified: 2012-05-06
I have a HoH and an empty hash, I would like to push the values of the $key into a hash. I started my code already but i need some help.
$key = 2;
$hash = {};
$interhash = { '1'=> {'crystal rock' => '1914'},
                       '2'=>{'design' => '6.0'}};

desired outcome:
$hash = {'design' => '6.0'};
if ($key =~ /^[+-]?\d+$/ && $alpha <= $key && $key <= $omega)#condition is necessary
        {
            push(@{$hash,{interhash}->{$value}});            
           
        }

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Question by:cucugirl
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Expert Comment

by:binkzz
ID: 24326802
hi,

I'm not sure why you're trying to push into an associative array. Are you expecting to have more than one value per key? If you'll only have one value per key, you can just simply say:

$hash{$key} = $value;
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Author Comment

by:cucugirl
ID: 24327354
The $key is a user's input, i put 2 here to make it  clearer.  If the key is 1 for example, i'd like the hash to look like this:

$key = 1;
$hash = {};
$interhash = { '1'=> {'crystal rock' => '1914'},
                       '2'=>{'design' => '6.0'}};

desired outcome:
$hash = {'crystal rock' => '1914'};
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Accepted Solution

by:
Adam314 earned 150 total points
ID: 24327532

#Reference to same data
$hash = $interhash{$key}
 
#copy of data
$hash = {%{$interhash{$key}}};

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Expert Comment

by:Callandor
ID: 24327609
Push and pop are used for arrays.  This is contrary to "I would like to push the values of the $key into a hash."  If you really want the results in a hash, then binkzz already provided the general technique: $hash{$key} = $value;

Now you have to pull a specific entry from a HoH using a key, and replace $value with that code.  The assignment then should be easy.
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Expert Comment

by:ozo
ID: 24327635

%hash = (%hash,%{$interhash{$key}})
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Expert Comment

by:Adam314
ID: 24327669
>>$hash{$key} = $value;
This would work if the variable was %hash (a hash variable).  The desired variable is $hash, which is a reference to a hash, not a hash.
The code I posted shows 2 ways: one having $hash refer to the same hash as the values of $interhash, and one having $hash refer to a new hash with the same data as the values of the values of $interhash.
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LVL 84

Expert Comment

by:ozo
ID: 24327739
$hash = {%$hash,map{%{$interhash->{$_}}} grep{/^[+-]?\d+$/ && $alpha <= $_ && $_ <= $omega} keys %$interhash}
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Author Comment

by:cucugirl
ID: 24327758
#copy of data
$hash = {%{$interhash{$key}}};

if i use this, i get the following error: Can't use an undefined value as a HASH reference but when i print interhash i have a HoH
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Assisted Solution

by:ozo
ozo earned 100 total points
ID: 24327809
that works for
%interhash = ( '1'=> {'crystal rock' => '1914'},
                       '2'=>{'design' => '6.0'});

for
$interhash = { '1'=> {'crystal rock' => '1914'},
                       '2'=>{'design' => '6.0'}};
it would be
$hash = {%{$interhash->{$key}}};

I made the same mistake in my first answer, and also misread $hash = {'design' => '6.0'}; with %hash = ('design' => '6.0');
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Expert Comment

by:ozo
ID: 24327922
note that unlike a push, $hash = {%{$interhash->{$key}}} deletes any keys that may have been in %$hash before

$hash = {(%$hash,%{$interhash{$key}}}
would be like push in that any keys that were in %$hash previously would remain (with possibly new values)
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