Re: doubts on perl Hash

use strict;
use warnings;
use feature qw( say );

my @aa = ("A", "C", "D", "E", "F", "G", "H", "I", "K", "L", "M", "N", 
+"P", "Q", "R", "S", "T", "V", "W", "Y");

my $pair;
for my $n1 (@aa) {
   for my $n2 (@aa) {
     $pair = $n1 . $n2;    
               
   }
}
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these are the 20 amino acids and i have to make 400 possible combination of two amino acid (di amino acid) like this:

AA AC AD ...... CA CC CD CE CF CG.....YA.....YY
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I TRIED TO MODIFY THE CODE but the scope of "for" loop diminishes when it ends. why it is ending there only, since i made the variable $pair as global only giving two Y's as output

Comment on Re: doubts on perl Hash Select or Download Code

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Re^2: doubts on Perl hash
by Athanasius (Archbishop) on Jul 08, 2017 at 05:55 UTC

The code shown has no output: it simply overwrites the value of $pair with a new value on each iteration of the nested loops. So, if you add the statement say $pair; after both loops have finished, of course you see only the last value of $pair, which happens to be YY.

To get all the values, you need to move the say statement into the inner loop:

use strict;
use warnings;
use feature qw( say );

my @aa = qw(A C D E F G H I K L M N P Q R S T V W Y);
my $pair;

for my $n1 (@aa)
{
    for my $n2 (@aa)
    {
        $pair = $n1 . $n2;    
        say $pair;
    }
}
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As an alternative, you could store the pairs in an array and output them after the loops have finished:

use strict;
use warnings;
use feature qw( say );

my @aa = qw(A C D E F G H I K L M N P Q R S T V W Y);
my @pairs;

for my $n1 (@aa)
{
    for my $n2 (@aa)
    {
        push @pairs, $n1 . $n2;
    }
}

say for @pairs;
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Hope that helps,

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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