Ndtyjky

I need to print comma "," when the list more than one, and if more than one, the last list I don't want to print comma. I know I can use Join to to do this but I can't loop @NAMES with comma if there is another @FAMILIES to add in.

#!/usr/bin/perl

use strict;

use warnings;



my @NAMES       = qw(ALLIES BOBBY CAKRA);

my @FAMILIES    = qw(A B C);





foreach my $names (@NAMES)

{

       foreach my $families (@FAMILIES)

       {

       print "$names, // $familiesn";

       }

}

Expected Outcome:

ALLIES, // A

ALLIES, // B

ALLIES, // C

BOBBY, // A

BOBBY, // B

BOBBY, // C

CAKRA, // A

CAKRA, // B

CAKRA // C

I don't see that there is an elegant and clean way since you need to drop the comma on the last element of both arrays. Then add an explicit condition, while iterating over indices so to be able to single out the last elements

use warnings;

use strict;

use feature 'say';



my @names       = qw(ALLIES BOBBY CAKRA);

my @families    = qw(A B C);



for my $n (0..$#names) {

    for my $f (0..$#families) {

        say $names[$n], 

            ( ($n == $#names and $f == $#families) ?  ' // ' : ', // '),

            $families[$f];

    }   

}

The parenthesis in the condition of the ternary operator ( ? : ) are needed for precedence. Another way is to use && instead of and, which binds more tightly, but I didn't want the code to rely on
a specific operator.

The syntax $#ary is for the index of the last element of @ary.

Special casing the last element is always messy, there are a bunch of trade offs, you just end up choosing which one looks less bad to you.

Another option compared to @zdim's perfectly good solution.

Note that I'm going to change @names and @families during execution, more tradeoffs, copying the array is the easy fix if it is a problem.

#!/usr/bin/perl

use strict;

use warnings;



my @names       = qw(ALLIES BOBBY CAKRA);

my @families    = qw(A B C);



my $last_name = pop(@names);



foreach my $names (@names)

{

       foreach my $families (@families)

       {

           print "$names, // $familiesn";

       }

}



my $last_family = pop(@families);



foreach my $families (@families)

{

       print "$last_name, // $familiesn";

}



print "$last_name // $last_familyn";

Using join would generally be the best answer, but that would only work if you want to prevent a comma at the end of the line. (At least for a straight-forward answer, I'm sure you could hack it.)

You can make use of Perl's $#array_name variables inside a for loop to check when you're at the end of both lists, like so:

#!/usr/bin/perl

use strict;

use warnings;





my @names       = qw(ALLIES BOBBY CAKRA);

my @families    = qw(A B C);



for my $i (0..$#names) {

    for my $j (0..$#families) {

    print "$names[$i]" . ($i == $#names && $j == $#families ? ' ' : ', ') . "// $families[$j]n";

    }

}

Also, a just a note on style: the Perl Style Guide (try perldoc perlstyle) recommends using all-capital variable names only when they're constants. It's not a big deal, and definitely not required, but it can make it a little easier for others to follow your code. :)

The alternative is to separate the output from the cross-product generation, and handling the last cast specially.

my @cross_product;

for my $n (0..$#names) {

    for my $f (0..$#families) {

       push @cross_product, [ $n, $f ];

    }   

}



if (@cross_product) {

   say "$_->[0], // $_->[1]" for @cross_product[0..@cross_product-2];

   say "$_->[0] // $_->[1]" for $cross_product[-1];

}

You can even avoid using up any memory as follows:

use Set::CrossProduct qw( );



my $i = Set::CrossProduct->new([ @names, @families ]);

my $N = $i->cardinality;

say sprintf '%1$s%3$s // %2$d', $i->get(), $_?',':'' for -$N+1..0;

I thought of a variation to ikegami's (storing the results in a temporary array). There would be too many changes to comfortably fit in a comment, so here:

You could store the comma to the temporary list, too, and then remove it from only the last line.

#!/usr/bin/perl

use strict;

use warnings;



my @names         = qw(ALLIES BOBBY CAKRA);

my @families      = qw(A B C);

my @output_lines;



foreach my $name (@names) {

    foreach my $family (@families) {

        push @output_lines, [$name, ',', ' // ' . $family . "n"];

    }

}



if (@output_lines) {

    $output_lines[-1][1] = '';  # remove comma from last line

    print map { @$_ } @output_lines;

}