Solved

copying array of hashes

Posted on 2009-05-10
6
239 Views
Last Modified: 2012-05-06
how can I make a copy of an array of hashes so that the original one isn't affected? I don't have use storage in my PERL version
0
Comment
Question by:cucugirl
6 Comments
 
LVL 84

Accepted Solution

by:
ozo earned 84 total points
ID: 24349370
@array=({k1=>'v1',k2=>'v2'},{k1=>'v1',k2=>'v2'});
@copy=map{{%$_}}@array;
$copy[1]{k2}++;
print "$copy[1]{k2} $array[1]{k2}\n";
0
 
LVL 39

Expert Comment

by:Adam314
ID: 24351547
>>I don't have use storage
I'm assuming you meant you don't have the Storable module?  If so, can you install it?  Have you tried?  Did you get an error?
0
 
LVL 5

Assisted Solution

by:vikaskhoria
vikaskhoria earned 83 total points
ID: 24352113
Check my script below:
(This deletes elements from the hash and the original hash is modified to the desired hash)

Thanks,
Vikas.

#!/usr/bin/perl
 
my %my_hash = ('TEST' =>'T' ,'QUIZ'=>'4','HWORK'=>'3');
my @table = ( {'TEST'=>'T'}, {'TEST'=>'F'},{'QUIZ'=>'1'},{'QUIZ'=> '2'},{'HWORK'=>'3'}, {'HWORK'=>'3'});
 
for my $value (keys %my_hash)
{
        my $found = 0;
        foreach $i (0 .. @table-1)
        {
                if ( $table[$i]{$value} == $my_hash{$value} ) {
                        $found = 1;
                }
        }
        if ( ! $found )
        {
                delete($my_hash{$value});
        }
}

Open in new window

0
 
LVL 5

Expert Comment

by:vikaskhoria
ID: 24361590
Check this link below:
http://www.perlmonks.org/?node_id=93693

This talks about copying array of hashes.
This may be of some help to you.
0
 
LVL 26

Assisted Solution

by:wilcoxon
wilcoxon earned 83 total points
ID: 25953183
The best way is to use Clone (this handles any level of nested structures).  Alternately, if you know that the hashes only contain scalars, it's easy to copy them manually.
my $orig = [{first=>1,second=>2},{first=>3,second=>4}]; 
# using Clone
use Clone qw(clone);
my $copy = clone($orig); 
# manually copying
## slow/inefficient way
my $copy = [];
foreach my $el (@$orig) {
    my %tmp;
    foreach my $key (%$el) {
        $tmp{$key} = $el->{$key};
    }
    push @$copy, {%tmp};
}
## better way
my $copy = [];
foreach my $el (@$orig) {
    push @$copy, {%$el};
}
## ozo's way - more succinct but should be about same performance (I think)
my $copy = [map { {%$_} } @$orig];

Open in new window

0

Featured Post

Networking for the Cloud Era

Join Microsoft and Riverbed for a discussion and demonstration of enhancements to SteelConnect:
-One-click orchestration and cloud connectivity in Azure environments
-Tight integration of SD-WAN and WAN optimization capabilities
-Scalability and resiliency equal to a data center

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Many time we need to work with multiple files all together. If its windows system then we can use some GUI based editor to accomplish our task. But what if you are on putty or have only CLI(Command Line Interface) as an option to  edit your files. I…
There are many situations when we need to display the data in sorted order. For example: Student details by name or by rank or by total marks etc. If you are working on data driven based projects then you will use sorting techniques very frequently.…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…

840 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question