copy subarray - Perl

On Fri, Mar 7, 2008 at 5:10 AM, Philipp Knechtle <philippk@evolva.com> wrote:
> Hi
> I am working with subarrays in a main array. When I copy the main array:
>
> my @mainarray = ([1,2,3],[4,5,6],[7,8,9])
> my @arraytwo = @mainarray
>
> the references get copied. When I then modify the subarray data in
> @arraytwo they are of course also modified in @mainarray.
>
> So I use the command:
>
> push @arraytwo, [@{$_}] for @mainarray
>
> to copy the array. Is there a nicer way to do it?

What you want is a deep copy. The easiest way to get a deep copy is
to use dclone from Storable*:

#!/usr/bin/perl

use strict;
use warnings;

use Data:umper;
use Storable qw<dclone>;

my @mainarray = ([1,2,3],[4,5,6],[7,8,9]);
my @arraytwo = @{dclone(\@mainarray)};

@{$arraytwo[0]} = reverse @{$arraytwo[0]};

print Dumper(\@mainarray, \@arraytwo);

* see perldoc Storable or http://perldoc.perl.org/Storable.html

--
Chas. Owens
wonkden.net
The most important skill a programmer can have is the ability to read.

In python or C++ there is a concept called "deep copy".
try to search that keyword on cpan, like this one:
http://search.cpan.org/~stevan/Class...s/Cloneable.pm

On Fri, Mar 7, 2008 at 6:10 PM, Philipp Knechtle <philippk@evolva.com> wrote:
> Hi
>
>
>
> I am working with subarrays in a main array. When I copy the main array:
>
>
>
> my @mainarray = ([1,2,3],[4,5,6],[7,8,9])
>
> my @arraytwo = @mainarray
>
>
>
> the references get copied. When I then modify the subarray data in
> @arraytwo they are of course also modified in @mainarray.
>
>
>
> So I use the command:
>
>
>
> push @arraytwo, [@{$_}] for @mainarray
>
>
>
> to copy the array. Is there a nicer way to do it?
>
>
>
>

From: "Philipp Knechtle" <philippk@evolva.com>
To: <beginners@perl.org>
> I am working with subarrays in a main array. When I copy the main array:
>
> my @mainarray = ([1,2,3],[4,5,6],[7,8,9])
> my @arraytwo = @mainarray
>
> the references get copied. When I then modify the subarray data in
> @arraytwo they are of course also modified in @mainarray.
>
> So I use the command:
>
> push @arraytwo, [@{$_}] for @mainarray
>
> to copy the array. Is there a nicer way to do it?

http://search.cpan.org/search?query=Clone&mode=module

Jenda
===== Jenda@Krynicky.cz === http://Jenda.Krynicky.cz =====
When it comes to wine, women and song, wizards are allowed
to get drunk and croon as much as they like.
-- Terry Pratchett in Sourcery

Philipp Knechtle wrote:
> Hi

Hello,

> I am working with subarrays in a main array. When I copy the main array:
>
> my @mainarray = ([1,2,3],[4,5,6],[7,8,9])
> my @arraytwo = @mainarray
>
> the references get copied. When I then modify the subarray data in
> @arraytwo they are of course also modified in @mainarray.
>
> So I use the command:
>
> push @arraytwo, [@{$_}] for @mainarray
>
> to copy the array. Is there a nicer way to do it?

For your simple AoA example:

my @arraytwo = map [@$_], @mainarray;



John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall