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Programming > Perl Beginners Cgi > Re: packing an ...
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Re: packing an array of hashes

by rcook@[EMAIL PROTECTED] Aug 8, 2007 at 10:01 AM

> I've re-read perlref and have been trying to tease an answer out of the
> Perl Cookbook.
>
> If you put a hash reference into an array
>      push @[EMAIL PROTECTED]
 \%hash;
> you do not store any actual hash data in the array.
> So if you change the hash, then later pull the hash reference from the
> array and access it, you get changed data.
> If you do this in a loop, you store an array of references to the exact
> same hash, rather than lots of different hashes.
> At least, this seems to be what's happening to me in the pseudo code
> below:
>
> Question: Is there an efficient way (resembling push @[EMAIL PROTECTED]
 \%hash) to
> do this that will work? Or do I need to 'unpack' the hash into key =>
> value notation to truly add the hash as an element in an array?
>
> while ( condition ) {
>      (add data to %address)
>      push @[EMAIL PROTECTED]
 \%address;
>      # print statement here shows the hash is different each time
> through the loop
> }
>
> for (@[EMAIL PROTECTED]
){
>      %h = %{$_};
>      for (keys %h) {
>          print "$_ = $h{$_}\n";
>         # print statement here prints the same hash over and over
>      }
>



You have sort of solved it yourself.

# print statement here shows the hash is different each time through the
loop

NO, it shows the data in the hash is different each time through, the hash
reference is the same reference

# print statement here prints the same hash over and over

YES, that's because the same hash reference is being stored.

Just need differentiating between a reference and its data



Owen
 




 5 Posts in Topic:
packing an array of hashes
ccosner@[EMAIL PROTECTED]  2007-08-07 16:47:06 
Re: packing an array of hashes
shawnhcorey@[EMAIL PROTEC  2007-08-07 20:01:12 
Re: packing an array of hashes
ccosner@[EMAIL PROTECTED]  2007-08-07 17:27:11 
Re: packing an array of hashes
rcook@[EMAIL PROTECTED]   2007-08-08 10:01:27 
Re: packing an array of hashes
mritty@[EMAIL PROTECTED]   2007-08-08 10:26:45 

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