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

Hi, I have a simple code below: 
sub get_lower_level_ehms_count()
{
        my %design_hash   = %{@_[0]}; local %ehm_count;

        ##Checking if the design has embedded SMSes
        if($design_hash{'EMBEDDED_HMS'})
        {
                my @ehms = @{$design_hash{'EMBEDDED_HMS'}}; ##Getting 
+the list of EHMs under the current DHM
                foreach(@ehms)
                {
                        my %ehm_hash = %{$_};
                        my $design_top = $ehm_hash{'TOP'};
                        
                        if($ehm_hash{'EMBEDDED_HMS'})
                        {
                                &get_lower_level_ehms_count(\%ehm_hash
+);
                        }
                        
                        if(!($ehm_count{$design_top}))
                        {
                                $ehm_count{$design_top} = @{$ehm_hash{
+'INSTANCES'}}; 
                        }
                        else
                        {
                                my $count = $ehm_hash{$design_top};
                                my $instances = @{$ehm_hash{'INSTANCES
+'}};
                                $count = $count + $instances;
                                $ehm_count{$design_top} = $count;

                        }

                }
        }

        return \%ehm_count;
}

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Here: ehm_count is the hash that I want it to be local to the main procedure and same needs to be used during recursive calls as well . I dont see it happening. Please help. Thanks, -Karthik

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Re: Updating the same hash using recursion
by Athanasius (Archbishop) on Aug 20, 2014 at 06:24 UTC

    Hello mvkarthik,

    I moved your post from Perl Monks Discussion to Seekers of Perl Wisdom. Please update your post by adding <code> ... </code> tags to make it readable. In addition, a small driver script together with sample input and desired output would go a long way to explaining what you are trying to accomplish.

    From the node title, I gather you want to share a hash between recursive calls of the subroutine? You have:

    sub get_lower_level_ehms_count()
{
    my %design_hash = %{ @_[0] };
    local %ehm_count;
    ...

    [download]

    but, after the first call, this makes a local copy of the hash, so it’s effectively the same as using my here. (See local.) Perhaps you want something like this?

    {
    my %ehm_count;

    sub get_lower_level_ehms_count
    {
        ...
    }
}

    [download]

    A couple of other points:

    1. In sub get_lower_level_ehms_count() {, the parentheses () are a prototype specifying that the sub takes no arguments. This is clearly not what you want, since you access the first element of @_ within the sub. If you remove the prototype, you can also remove the initial ampersand (&) from the recursive call: get_lower_level_ehms_count(\%ehm_hash);. See perlsub#Prototypes.

    2. In the assignment my %design_hash = %{@_[0]};, @_[0] is actually an array slice. Since you are accessing only a single array element, this is better written as $_[0].

    Hope that helps,

    Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

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Re: Updating a same hash using recurrsion ...
by 2teez (Vicar) on Aug 20, 2014 at 06:10 UTC
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Re: Updating a same hash using recurrsion ...
by NetWallah (Canon) on Aug 20, 2014 at 14:41 UTC
    Untested, simplified code suggestion: 
    sub get_lower_level_ehms_count
{
        my %design_hash   = %{$_[0]};
        my %ehm_count ;
        my $embedded = $design_hash{'EMBEDDED_HMS'} or return \%ehm_co
+unt;
        for my $emb (@$embedded)
        {
             my $design_top = $emb->{'TOP'};
                        
             if($emb->{'EMBEDDED_HMS'})
             {
                    $lower_levels = get_lower_level_ehms_count($emb); 
                    $ehm_count{$_} += $lower_levels->{$_} for keys %$l
+ower_levels;
             }
             $ehm_count{$design_top} += scalar @{$emb->{'INSTANCES'}};
 
        }

        return \%ehm_count;
}

    [download]

            "You're only given one little spark of madness. You mustn't lose it."         - Robin Williams

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