How do you access an array element in Perl when you have the name of the array stored as an element of another array?

Question

Suppose I have this piece of code.

It has an array 'arr' storing the names of other arrays like 'et', 'rt' etc...

    #!/usr/bin/perl
    $\="\n";
    @arr = ("$et", "\$rt", "\$ee", "\$re", "\$ec", "\$epc", "\$rc", "\$rpc", "\$euc", "\$ruc", "\$ekc", "\$rkc");
    @et = (100, 1000, 1100, 1200, 200, 300, 400, 500, 600, 700, 800, 900);
    .
    .
    .

And other arrays rt, ee similarly defined..

How do I access say $et[2]? I've tried $arr[0][2], $($arr[0])[2] and many other variations but nothing seems to work. Any solution?

Check ARRAYS OF ARRAYS, HASHES OF ARRAYS, ARRAYS OF HASHES, HASHES OF HASHES => perldoc.perl.org/perldsc.html — mpapec
– mpapec, Commented Jan 7, 2014 at 8:38

Steffen Ullrich · Accepted Answer · 2014-01-07 08:25:12Z

2

It's a bad idea to work this way. What you probably want is not to store the names of other arrays, but references to it, e.g.

my @et = ( 100,1000,1100,1200,... );
my @arr = ( \@et,... )

then you can access the second element from @et using @arr with $arr[0][1]:

$arr[0] -> \@et (reference to @et)
$arr[0][1] -> second element of @et

often you see instead people write $arr[0]->[1], which is exactly the same, only 2 bytes longer :)

answered Jan 7, 2014 at 8:25

Steffen Ullrich

125k11 gold badges155 silver badges194 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Jonathan Leffler · Accepted Answer · 2014-01-07 08:32:08Z

2

You don't use use strict; (or, at least, not use strict refs;).

You need ${$arr[0]}[2], but you store the plain name ("et") in @arr:

@arr = ("et", "rt",);
@et = (100, 1000, 1100, 1200, 200, 300, 400, 500, 600, 700, 800, 900);

print ${$arr[0]}[2], "\n";

It isn't good style, though. You'd be better off using a hash indexed by 'array name' with the arrays (or array refs) as the value associated with the key:

my %arr = ( "et" => [100, 1000, 1100], "rt" => [200, 2000, 2200] );

print $arr{et}->[2], "\n";

answered Jan 7, 2014 at 8:32

Jonathan Leffler

759k145 gold badges961 silver badges1.3k bronze badges

Collectives™ on Stack Overflow

How do you access an array element in Perl when you have the name of the array stored as an element of another array?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related