Passing array reference to sub-routine 1

[varakal]

I am having problem with passing array reference to sub-routine. I think I should be doing a small mistake somewhere.

print "Above function: $data[0]\n";
my $line = array_refer("\@data");

sub array_refer {
        my @data = @$_[0];
        print "In function: $data[0]\n";
}

The output I get is:

Above function: 1234567
In function:

Where am I doing wrong? THanks in advance.

 

[KevinADC]

what is @data before you get to this part of your script?

You don't want to use the double-quotes in: array_refer("\@data")

just use: array_refer(\@data)

Is this what you are trying to do?:

my @data = (12345, 67890);

print "Above function: $data[0]\n";
my $line = array_refer(\@data);

sub array_refer {
        my ($array_ref) = @_;
        print "$array_ref->[0]\n";
}

 

[varakal]

In the function, I should have used like this:

my @data = @{@_[0]};
print "In function: $data1[0]\n";

But the main problem is quotes. Thanks Kevin for this.

Varakal

 

[KevinADC]

you can do it like that but it's unusual and completely unecessary. Don't use references when you don't need to. In that example you don't need to use a reference at all, but maybe you are just practicing and experimenting to see how perl references work.

 

[varakal]

I wanted to use that notation because, I will be using that array everywhere, and I would want to minimize the number of '->' or '$$' signs.
And also, am I using extra references there? I didnt get it. I felt that what all I am trying to do is copy the whole array the reference is pointing to, into a @data array?

 

[KevinADC]

to copy the whole array to the sub routine just do this:

my @data = (0 .. 100);

print "Above function: $data[0]\n";
my $line = array_refer(@data);

sub array_refer {
        my @data = @_;
        print "$data[0] $data[99]\n";
}

its very easy to pass a single array or a scalar or even a hash this way. The problem comes in when you want to pass more than one list to a sub routine because multiple lists are flattened in the system array @_ and become one long list. To avoid this flattening of lists you pass references to a sub routine:

my @digits = (0 .. 100);
my @alphas = ('a' .. 'z');

&array_refer(\@digits,\@alphas);

sub array_refer {
        my @digits = @{$_[0]};
        my @alphas = @{$_[1]};
        print "$digits[10] $alphas[10]\n";
}

 

[varakal]

That is true. As a programmer in other languages, I was never into the idea of sending the array as flattened list.
Thanks
Varakal