a reference to an element of an array or hash: how to create?

arifsaha has asked for the wisdom of the Perl Monks concerning the following question:

Hi!

Do you know how to create a reference to an element of an array or hash? For instance I have an array @a, and I like $a2r contains a reference to $a[2]. Anyway to do it in Perl?

Keep in mind this is not the case where $a[2] contain a reference and $a2r contains the same reference, but instead $a2r contain a reference to the scalar stored in $a[2].

Let me explain more using the pseudo code below, RefTo represent the mechanism in question:

my @a= (1, 2, 3, 4);

my $p= RefTo $a[2];

$$p= 9;

print join(",", @a) # should print 1,2,9,4
[download]

So, any idea wether there is such mechanism as RefTo in Perl?

-- 
S P Arif Sahari Wibowo
http://www.arifsaha.com/

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Re: a reference to an element of an array or hash: how to create? by Fletch (Bishop) on Aug 05, 2008 at 14:20 UTC
The normal reference operator `\` works just fine for elements of aggregates. `use Data::Dumper qw( Dumper ); my @a = ( 1, 2, 3, 4 ); print Dumper( \@a ); $x = \$a[2]; $$x = 9; print Dumper( \@a ); exit 0; __END__ $VAR1 = [ 1, 2, 3, 4 ]; $VAR1 = [ 1, 2, 9, 4 ];` [download] The cake is a lie. The cake is a lie. The cake is a lie.	[reply] [d/l] [select]
Re: a reference to an element of an array or hash: how to create? by FunkyMonk (Bishop) on Aug 05, 2008 at 14:22 UTC
The same way you'd make a reference to any other structure: the backslash operator: `my $p = \$a[2];` [download] Unless I state otherwise, all my code runs with strict and warnings	[reply] [d/l]
Re^2: a reference to an element of an array or hash: how to create? by arifsaha (Acolyte) on Aug 05, 2008 at 15:04 UTC
Duh! I should try it first, didn't think it will be that easy before. Thanks everyone! -- S P Arif Sahari Wibowo http://www.arifsaha.com/	[reply]
Re: a reference to an element of an array or hash: how to create? by toolic (Bishop) on Aug 05, 2008 at 14:39 UTC
In addition to the other advice given, you may find this useful: References quick reference	[reply]
Re: a reference to an element of an array or hash: how to create? by pjotrik (Friar) on Aug 05, 2008 at 14:22 UTC
`#!/usr/bin/perl use warnings; use strict; my @array = qw(1 2 3 4); my $r = \$array[2]; $$r = 5; print @array;` [download]	[reply] [d/l]
Re: a reference to an element of an array or hash: how to create? by dHarry (Abbot) on Aug 05, 2008 at 14:28 UTC
Use a \ `use strict; use warnings; my @a= (1, 2, 3, 4); my $p= \$a[2]; print $$p;` [download] See perlreftut for details	[reply] [d/l]