Re^2: Array slices: beyond the end/ Assigning an empty list to a Hash slice


"be consistent"
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Re^2: Array slices: beyond the end/ Assigning an empty list to a Hash slice

by 7stud (Deacon)

on Mar 22, 2014 at 19:09 UTC ( [id://1079399]=note: print w/replies, xml )

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in reply to Re: Array slices: beyond the end/ Assigning an empty list to a Hash slice
in thread Array slices: beyond the end/ Assigning an empty list to a Hash slice

Your question here seems to imply an assumption. This might be: "Why is indexing beyond the end of the list legal for a slice when it's illegal for an array?

Yes, I think I was confused by that because I did this:

use strict;
use warnings;
use 5.014;  

my @arr = ();

if (exists $arr[0]) {
    say 'yes';
}
else {
    say 'no';
}

say $arr[0];

--output:--
no
Use of uninitialized value in say at 1.pl line 15.
[download]

And the error convinced me that you can't index beyond the end of the array, but as you pointed out and as "Learning Perl" (6th) says on p. 45:

If the subscript indicates an element that would be beyond the end of the array, the corresponding value will be undef.

For comparison:

my @arr = (undef);

if (exists $arr[0]) {
    say 'yes';
}
else {
    say 'no';
}

say $arr[0];

--output:--
yes
Use of uninitialized value $arr[0] in say at 1.pl line 14.
[download]