Re^2: Generate Array of Hashes WITHOUT References

Thanks for your reply, Rolf.

> Fascinating how most replyers misunderstood you're question, cause they read the title but not the code.

I didn't notice. Which posts are you refering to?

> This is wrong
> $rec=();
> You need to write %rec=() because you don't want references.

Sorry - typo on my part (that is what I meant to type). However, but after making that change in my code below:

#!/usr/bin/perl

use Data::Dumper;
use warnings;

while ( <DATA> ) {
        #$rec = {};
        #$rec = ();
        %rec = ();
        for $field ( split ) {
                ($key, $value) = split /=/, $field;
                $rec{$key} = $value;
        }
        push @AoH, \%rec;
}
print Dumper(\@AoH);
__DATA__
A=1 B=2 C=3
Y=4 Z=5
[download]

...which includes the change of push'ing \%rec, I get this output:

$VAR1 = [
          {
            'Z' => '5',
            'Y' => '4'
          },
          $VAR1->[0]
        ];
[download]

Which is wrong, but if I change "%rec = ();" to "my %rec;" (as per Anonymous Monk's solution), I get what I want:

$VAR1 = [
          {
            'A' => '1',
            'C' => '3',
            'B' => '2'
          },
          {
            'Z' => '5',
            'Y' => '4'
          }
        ];
[download]

Any ideas why? What's the significant difference between "%rec = ();" and "my %rec;" in this case?

> WHY don't you use warnings ??

No good reason (force of (bad) habit), but apart from the reason you mentioned in a later post, having tried "use warnings" in my code now (as above), it looks as if it would not have reported any problem. "use strict" may have helped.

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Re^3: Generate Array of Hashes WITHOUT References by parv (Parson) on Sep 10, 2014 at 14:34 UTC
`$VAR1 = [ { 'Z' => '5', 'Y' => '4' }, $VAR1->[0] ];` [download] The second element refers to the first element of the array reference. If `$Data::Dumper::Deepcopy = 1;`, then you will see that both array elements are the same. The problem is of variable scoping; see Coping with Scoping. I will try to explain but do wait for better\|clearer explanation. Without my function, the hash `%rec` has scope file-wide (outside of the loop). The reference to the hash refers to that hash, the only copy. So modifying the only copy of the hash overwrites previous values (see by `for { ... } print Dumper( \%rec ) ;`). As the reference to the hash is saved twice, same values are repeated in `Dumper()` output. Use of `my` function inside the `while` loop limits the scope of `%rec` within the loop. On each iteration a spanking new hash is allocated, saving the values as references to each separate hash in the array as expected.	[reply] [d/l] [select]
Re^4: Generate Array of Hashes WITHOUT References by tel2 (Pilgrim) on Sep 10, 2014 at 23:00 UTC
Well explained, AF. Thanks for that! I tried `$Data::Dumper::Deepcopy = 1;`, and I see what you mean. One thing I don't understand is what you mean by: see by `for { ... } print Dumper( \%rec ) ;` I'd like to try that code, but what exactly should I type, coz the syntax doesn't look right yet?	[reply] [d/l] [select]
Re^5: Generate Array of Hashes WITHOUT References by Anonymous Monk on Sep 11, 2014 at 07:11 UTC
To start ... `...` means fill in the code as appropriate (and, author was too lazy to provide the whole thing not directly related to the point); `for { ... }` is a reference to `for` loop code inside `while` loop; then, `print` statement would go right after `for` loop. ... so `for { ... } print Dumper( \%rec ) ;` expands to ... `... while ( <DATA> ) { ... for $field ( split ) { ... } print Dumper( \%rec ) ; push @AoH, \%rec; } ...` [download]	[reply] [d/l] [select]