HofA - Sum Totals

drodinthe559 has asked for the wisdom of the Perl Monks concerning the following question:

Perl Experts: I have the following snippet that doesn't sum all the credits for companies in the hash. The person who helped me used $_, but nothing seems to go into the variable.

foreach $company (sort(keys %details_for)){
   my @trans_details = @{$details_for{$company}};
   my $comp = $trans_details[0]->{'company'};
   my $sumcredits += $_->{'credits'} for (@trans_details);

    #Show the total credits
    print $comp, "\t", $sumcredits, "\n";
};
[download]

Help over this speed bump would be appreciated. I'm pretty close to finishing this.

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Re: HofA - Sum Totals by ikegami (Patriarch) on Feb 22, 2010 at 23:45 UTC
It's impossible for nothing to go into `$_` if the code that uses `$_` gets executed. `$_` is being aliased to each element of `@trans_details` in turn, so `$_` will contains whatever they contain. If the value of `$_` doesn't change, it's because the value of the elements are the same. ~~In other words, the bug is elsewhere.~~ Update: As kennethk discovered, there is a problem with the code you posted. The problem isn't with `$_`, though. I wonder how you came to the conclusion that it was.	[reply] [d/l] [select]
Re: HofA - Sum Totals by kennethk (Abbot) on Feb 22, 2010 at 23:40 UTC
There is nothing obviously wrong with this code and I gain no new insight from reading what I presume was the previous node in this thread, Query Array from Hash. Please give some sample input data, or even better the output generated by Dumper (Data::Dumper) so we can compare the data structure you have to the one your code expects. The my is localizing your result to the implicit for loop. Try this instead: `my $sumcredits = 0; for (@trans_details) { $sumcredits += $_->{'credits'} }` [download]	[reply] [d/l]
Re^2: HofA - Sum Totals by drodinthe559 (Monk) on Feb 23, 2010 at 21:22 UTC
That worked. It also worked like the following: `my $sumcredits = 0; $sumcredits += $_->{'credits'} for (@trans_details);` [download] So the value in how I had it setup before kept on reinitializing every time it went through the loop. Thanks for your help.	[reply] [d/l]
Re: HofA - Sum Totals by Your Mother (Archbishop) on Feb 22, 2010 at 23:43 UTC
Slight style/syntax mods with debug stub. `use YAML; for my $company ( sort keys %details_for ) { my @trans_details = @{ $details_for{$company} }; my $comp = $trans_details[0]->{company}; my $sumcredits; $sumcredits += $_->{credits} for @trans_details; # Uncomment to see if the "credits" are there as expected. # print Dump($details_for{$company}); # Show the total credits printf("%20s --> %.2f\n", $comp, $sumcredits); }` [download]	[reply] [d/l]