For loop help in perl - perl

Question

I am writing perl script and I have little question regarding for loop limit.
Let say I have two arrays, arr1 has serial numbers and arr2 is two dimensional array, the first dimension is the serial number [same as arr1] and the second dimension is the contents of that serial number , Now I want to apply the for loop for this two dimension array but I am confused at the limit . Till now I have this code
Example : I have Three serial numbers , 1 ,2 ,3 . Serial 1 has 2 contents 1,5 . Serial 2 has 1 content i.e 1. Serial 3 has two contents 1,1.
#arr1 = (1,2,3)
$arr2[0][0] = 1
$arr2[0][1] = 5
$arr2[1][0] = 1
$arr2[2][1] = 1
$arr2[2][2] = 1
Note: As you can see the contents of arr2 has arr1 elements in 1st columns and the contents in the second columns.
for (my $i = 0; $i <= $#arr1; $i++) {
print( "The First Serial number has:" );
for (my $j = 0; $j <= $#arr2; $j++) {
print( "$arr2[$i][$j]\n" );
}
}
Thanks, Sorry for the bad explaination

Answer 1

Why don't do this like that :
#!/usr/bin/perl
use strict;
my #arr;
$arr[0][0] = 1;
$arr[0][1] = 5;
$arr[1][0] = 1;
$arr[2][1] = 1;
$arr[2][2] = 1;
my ($i, $j);
foreach $i (#arr) {
foreach $j (#{$i}) {
print $j."\n" if($j);
}
}
1;
__END__

Answer 2

Fixed code:
use strict;
use warnings;
my #arr1 = (1,2,3);
my #arr2;
$arr2[0][0] = 1;
$arr2[0][1] = 5;
$arr2[1][0] = 1;
$arr2[2][0] = 1; # original code had
$arr2[2][1] = 1; # these indexes wrong
for (my $i = 0; $i <= $#arr1; $i++) {
print( "Serial number $arr1[$i] has:" );
for (my $j = 0; $j <= $#{ $arr2[$i] }; $j++) {
print( "$arr2[$i][$j]\n" );
}
}
Note the use of $#{ arrayref }; see http://perlmonks.org/?node=References+quick+reference

Answer 3

you can put #arr2 like this and it would be much easier for you to understand #arr2
use strict;
use warnings;
my #arr1 = (1, 2, 3);
my #arr2 = ([1, 5], [1], [1, 1]);
for my $first(#arr1) {
for my $second (#{$arr2[$first-1]}) {
print $second."\n";
}
}

Answer 4

Here is a version without the first array.
for (my $i = 0; $i<= $#arr; $i++)
{
print "INDEX $i\n";
for (my $j = 0; $j <= $#{$arr[$i]}; $j++)
{
print "${arr[$i][$j]}\n";
}
}
The point here is that a two dimensional array is in fact an array of arrays (well actually array references, but that does not change anything here). So in the inner loop, you should check against the size of the array that is stored in $arr[$i].

Answer 5

Try this.
my #arr2;
$arr2[0][0] = 1;
$arr2[0][1] = 5;
$arr2[1][0] = 1;
$arr2[2][0] = 1;
$arr2[2][1] = 1;
foreach $inside_array (#arr2){
foreach $ele (#$inside_array){
print $ele,"\n";
}
}
Its always better to use foreach instead of for/while, this will eliminate any possibility of bugs. Especially with judging proper condition to exit the loop.