austinj has asked for the wisdom of the Perl Monks concerning the following question:

I have a subroutine which calls itself and I would like to have an array within it which is all of the keys within a nested array/hash I think I need it to remember the variable but I don't want to create a global variable. Here was my attempt. The hash looks something like this: 
{
batchplot_output_filename => "gps3", 
plot_all_variables => 'off', 
# DEFAULT PLOTS & VALUES
default_values =>
[
{
profiles => [qw(prof1 prof2)],

linewidth => ["2"],
single_dotnotes => 'On',
legend => ["On"],
},
],
#BEGIN CUSTOM PLOTS
custom_plots =>
[
  [ 
    {
        yvars => 'LATDIIP',
        xvars => 'ELONGI',
    },
  ],
]
}

[download]
sub analyse_user_inputs {
    my $hashORarray_ref = shift @_;
    my @the_inputs;
    
    foreach ( keys %{$hash_ref} ){
#        print "$_ \n";
    push(@the_inputs , $_);
        if (ref $hash_ref->{$_} eq 'HASH') {
            analyse_user_inputs($hash_ref->{$_});
        }
    elsif(ref $hash_ref->{$_} eq 'ARRAY'){
       foreach my $array_element (@{$hash_ref->{$_}}){
#          if(ref $info eq 'ARRAY'){
#             foreach my $element (@{$info}){
#                    analyse_user_inputs($element);
#             }
#          }
#          if (ref $info eq 'HASH') {
                 analyse_user_inputs($array_element);
#              }          
       }
    }
    }
    print Dumper(\@the_inputs);
    return(\@the_inputs);
}

[download]

Replies are listed 'Best First'.
Re: subroutine memory variable scope
by NetWallah (Canon) on Dec 13, 2012 at 16:29 UTC
    You don't seem to be using @the_inputs for anything useful, and you throw away the returned value, at least in the internal recursive calls.

    Iterating over the inputs for a given recursion will take care of itself - I don't see a need to save the list for posterity.
    I would suggest getting rid of it entirely, since you have shown no use for it.

                 "By three methods we may learn wisdom: First, by reflection, which is noblest; Second, by imitation, which is easiest; and third by experience, which is the bitterest."           -Confucius

[reply]
      Maybe I'm not understanding. I need the @the_inputs to be returned from the subfunction - I will be using it in a later call to verify if the user supplied inputs are valid ones.
[reply]
Re: subroutine memory variable scope
by tobyink (Canon) on Dec 13, 2012 at 17:12 UTC

    You're maybe looking for something like this?

    use strict;
use warnings;

sub analyse_user_inputs {
    my $hash_ref = shift @_;
    my @the_inputs;

    foreach ( keys %{$hash_ref} ) {
        push @the_inputs, $_;
        if (ref $hash_ref->{$_} eq 'HASH') {
            push @the_inputs, @{ analyse_user_inputs($hash_ref->{$_}) 
+};
        }
        elsif (ref $hash_ref->{$_} eq 'ARRAY') {
            foreach my $array_element (@{$hash_ref->{$_}}){
                push @the_inputs, @{ analyse_user_inputs($array_elemen
+t) };
            }
        }
    }
    
    return(\@the_inputs);
}

my $data = {
    foo => 1,
    bar => [
        {
            xyzzy => 'magic',
        }
    ],
    baz => {
        quux => 123,
    }
};

use Data::Dumper;
print Dumper(analyse_user_inputs($data));

    [download]

    No need to play funny tricks with variable scoping. Just take the results of your recursive calls and push them onto @the_inputs.

    perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
[reply]
[d/l]
[select]

      I think this is close - I made a few changes but I am still only getting the 1st tier of keys when I really want all sublevels of keys. I would like $user_inputs to be an array ref which contains:

      profiles, linewidth, single_dotnotes, legend, xvars, yvars

      when I try pushing the return of the subfunction I get a bunch of wierd empty returns

      function call

      my $user_inputs = analyse_user_inputs($Settings);
print Dumper($user_inputs);

      [download]

      incoming hash/array combo

      $Settings =
{
batchplot_output_filename => "gps3", 
plot_all_variables => 'off', 
# DEFAULT PLOTS & VALUES
default_values =>
[
{
profiles => [qw(prof1 prof2)],
linewidth => ["2"],
single_dotnotes => 'On',
legend => ["On"],
},
],
#BEGIN CUSTOM PLOTS
custom_plots =>
[
  [ 
    {
        yvars => 'LATDIIP',
        xvars => 'ELONGI',
    },
  ],  
]
}

      [download]

      subfunction

      sub analyse_user_inputs {
    my $hashORarray_ref = shift @_;
    my @the_inputs;
        
if (ref $hashORarray_ref eq 'HASH') {
   foreach ( keys %{$hashORarray_ref} ){
#      print "$_ \n";
      push @the_inputs , $_ ;
      analyse_user_inputs($hashORarray_ref->{$_});
   }
}
if (ref $hashORarray_ref eq 'ARRAY') {
   for (my $i = 0; $i < scalar(@{$hashORarray_ref}); $i++) {
      analyse_user_inputs($hashORarray_ref->[$i]);
   }
}
   return(\@the_inputs);
}

      [download]
[reply]
[d/l]
[select]

        "I made a few changes but I am still only getting the 1st tier of keys"

        Then undo the changes, because the code I posted returns all levels of keys.

        The key part which you stripped out is...

        push @the_inputs, @{ analyse_user_inputs(...) };

        [download]

        When you understand what that's doing, then you'll understand why you shouldn't have stripped it out.

        perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'
[reply]
[d/l]

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