CODEWITHSUNDEEP
arraysperl
Scra
Scra

Reputation: 137

Adding elements to an array in Perl

I have this code where I want to add 10, 11 and 12 to array arr.

my @num=(0,1,2);
my $i=10;
for my $d (@num){
   if (defined($d)) {
      my @arr;
      $arr[$d] = $i;
      $i=$i+1;
      my $dvv=dump(\@arr);
      print "**** $dvv \n";
   }
}

The output is:

**** [10]
**** [undef, 11]
**** [undef, undef, 12]

Why is only the last element of array defined?

Upvotes: 7

Views: 39999

Answers (2)

AntonH
AntonH

Reputation: 6437

Since you have the declaration of the array within the loop, it will re-create it each time, removing any values that would have been placed in it on previous iterations of the loop.

You should declaure @arr before the loop if you want the values to stay:

my @arr;
for my $d (@num) {
    ...
}

And because of this line:

$arr[$d];

$d is the position defined by the other array (0, then 1, then 2). So it puts the value of $i in that position in the array, and puts values before to undef.

Upvotes: 7

Matt Jacob
Matt Jacob

Reputation: 6553

AntonH's answer addresses the specific problem with your specific code, but there are actually ways to rewrite your code that would avoid the problem entirely. A more "Perlish" way to accomplish the same thing would be:

my @arr;

for my $i (0 .. 2) {
    push(@arr, $i + 10);
}

Or:

my @arr = map { $_ + 10 } 0 .. 2;

Or just:

my @arr = 10 .. 12;

Upvotes: 16

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