reference of hash

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

Hello Dear Monks

I am usin a hash reference in my program but I made a mistake. Could you check ? Thanks. I just wrote the parts where the problem lies. I have not written what has been tested.

I have updated the code with bits I found important to write

sub flow_count{
    
    my $HASH_OF_FLOW;
    my $view = $_[0]; # FTFM or CTFM

        ...
        ...
        foreach my $file(@FILES_IN_THE_FOLDER){
           my $key = "$reg;$date";
           # M2 is a number which has been computed
       $HASH_OF_FLOW->{'$key'} = 'M2';
        }

     return $HASH_OF_FLOW; 
}

my $FTFM_HASH_OF_FLOW = flow_count("FTFM");
my $CTFM_HASH_OF_FLOW = flow_count("CTFM");
my @FTFM_KEYS = keys %$FTFM_HASH_OF_FLOW;


foreach my $key(@FTFM_KEYS){
    my $FTFM_CTFM_diff = $FTFM_HASH_OF_FLOW{$key} - $CTFM_HASH_OF_FLOW
+{$key};
    print $OUTFILE "$key;$FTFM_HASH_OF_FLOW{$key};$CTFM_HASH_OF_FLOW{$
+key};$FTFM_CTFM_diff\n";
}
[download]

Comment on reference of hash Download Code

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Re: reference of hash by toolic (Bishop) on Jun 13, 2008 at 13:56 UTC
`$HASH_OF_FLOW->{'$key'} = 'M2';` [download] Single quotes prevent variable interpolation of `$key`. You probably want: `$HASH_OF_FLOW->{$key} = 'M2';` [download]	[reply] [d/l] [select]
Re: reference of hash by radiantmatrix (Parson) on Jun 13, 2008 at 14:52 UTC
I see a couple of problems: Inside `flow_count`, you say `$HASH_OF_FLOW->{'$key'} = 'M2'`. By surrounding `$key` with single quotes, you're getting the string '$key' rather than the value in the variable `$key`. Drop those quotes. In your foreach loop, you're not dereferencing your hashrefs. For example, where you say `$FTFM_HASH_OF_FLOW{$key}`, you should be saying `$FTFM_HASH_OF_FLOW->{$key}`. You're not using strict and warnings -- if you were, you'd have been scolded for #2, above. As an aside, you may want to read up on How (Not) To Ask A Question; it will advise you on how to get better responses. For example, providing the text of the error you're receiving would have been useful. You might also want to take a look at Data::Dumper; if you'd used that to inspect the contents of `$HASH_OF_FLOW`, you'd have very quickly seen problem #1. <–radiant.matrix–> Ramblings and references “A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort.” — Herm Albright I haven't found a problem yet that can't be solved by a well-placed trebuchet	[reply] [d/l] [select]