Square the array values.

[Anonymous Monk]

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Hi.. PERL Monks,

I'm new to this forum, I have a requirement, I want to
square the array values itself, ( without new array)


Example:

my @arr = qw( 1 2 3 4 5 6 7 8);

I need to change the array like the following without new array.

@arr = qw( 1 4 9 16 25 36 49 64);

Thanks in advance...

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[GrandFather]

I'd just:

my @arr = map {$_ * $_} qw( 1 2 3 4 5 6 7 8);

or if the array already exists:

$_ *= $_ for @arr;

[chromatic]

Somehow you have to loop through the array and modify the values in place with the exponentiation operator (or the multiplication operator). perlsyn describes most of the interesting parts in the section on "Foreach Loops".

[kiruthika.bkite]

Is this you are expecting.


use strict;
use warnings;
use Data::Dumper;


my @array=(1,2,3);
print Dumper \@array;
my $len=$#array;
while($len>=0)
{
        $array[$len]=$array[$len]*$array[$len];
        $len--;
}
print Dumper \@array;



Or use the following way.


my @array=(1,2,3);
foreach (@array)
{
        $_=$_*$_;
}

[chromatic]

The latter is much better, though you could multiply and assign in place with =*:

for (@array)
{
    $_ *= $_;
}

... or even use postfix iteration:

$_ *= $_ for @array;

[BrowserUk]

For completeness:

@a = 1..10;;
$_ **= 2 for @a;;
print @a;;
1 4 9 16 25 36 49 64 81 100

[Anonymous Monk]

Thanks to all..

[Marshall]

To modify the input array, pass an array reference to the subroutine.

#!usr/bin/perl -w
use strict;

my @arr = qw( 1 2 3 4 5 6 7 8); 
square(\@arr);

sub square
{
   my $arrayref = shift;
   foreach my $item (@$arrayref)
   {
      $item **=2; #or
     #$item *=$item;
   }
}

foreach (@arr)
{
   print "$_\n";
}
__END__
prints:
1
4
9
16
25
36
49
64

This will produce the same @arr, but not quite in the same way:

my @arr = qw( 1 2 3 4 5 6 7 8); 
foreach (@arr)
{
  $_*=$_;
}
#or 
@arr = map($_*$_}@arr;

[pajout]

Though it could be considered ugly, map can help you:

pajout@balvan:~$ perl -e 'my @a = (1,2,3); print join(",", map {$_*$_}
+ @a)."\n";'
1,4,9