Trouble passing hash and variable to subroutine

Question

I want to pass a hash and a variable to a subroutine:

%HoA = {'1'=>'2'};
my $group_size = 10;

&delete_unwanted(\%HoA,$group_size);

sub delete_unwanted {
    my (%HoA,$group_size) = @_;
    print "'$group_size'\n"
}

But, this prints nothing.

Answer 1

You're passing a hash reference (as you should), so therefore assign it to a scalar in your parameter catching:

sub delete_unwanted {
    my ($hashref, $group_size) = @_;

    print "'$group_size'\n"
}

If you later want to dereference it, you can my %newHoA = %$hashref;, but that will be a copy of the original hash. To access the original structure, just use the reference: print $hashref->{a_key};.

Answer 2

Your problem is in:

my (%HoA,$group_size) = @_;

You can solve it by saying, for example:

sub delete_unwanted {
    my $hashPointer = shift;
    my $group_size = shift

Note that you can retrieve the original hash inside the subroutine by either: de-referencing the hashPointer (my %HoA = %$hashPointer), or you can access the hash contents directly using the pointer directly (eg, $hashPointer->{'key'})