in reply to Re^2: Question of scope and syntax
in thread Question of scope and syntax

I followed your advice. I have narrowed my problem down to the comparison part of my code here: 
foreach (@contentsOfDataBase){
  chomp ($_);
  print "$_";
  @inDirectoryNotInDataBase = grep {!"$_"} @contentsOfDirectory;
  print "@inDirectoryNotInDataBase", "\n";
}

foreach (@copyOfContentsOfDirectory){
  print "$_";
  @pdfNoMatchingDirectory = grep (!$_, @contentsOfDataBase);
  print "@pdfNoMatchingDirectory", "\n";
  
}

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They're nearly identical so it is the same problem in both. I changed the structure of the grep function to see if that would fix it. It didn't. The problem specifically lies in the grep line itself. This is how I understand that block to work. 
foreach (@contentsOfDataBase){
  chomp ($_);
  print "$_";
  @inDirectoryNotInDataBase = grep {!"$_"} @contentsOfDirectory;
  print "@inDirectoryNotInDataBase", "\n";
}

foreach (@copyOfContentsOfDirectory){
  print "$_";
  @pdfNoMatchingDirectory = grep (!$_, @contentsOfDataBase);#for curre
+nt element in @copyOfContentsOfDirectory find all elements of @conten
+tsOfDataBase that are not a match
  print "@pdfNoMatchingDirectory", "\n";
  
}

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Re^4: Question of scope and syntax
by davido (Cardinal) on May 03, 2012 at 16:10 UTC

    The special variable, "$_" is used both by grep, and by foreach. Write your loop like this: 

    foreach my $dir_try ( @copyOfContentsOfDirectory ) {
    push @pdfNoMatchingDirectory, grep { $_ ne $dir_try } @contentsOfD
+ataBase;
}

    [download]

    The 'it' variable ($_) from your foreach loop is being masked by the it variable from the grep. This avoids that situation. Also, on each loop iteration, @pdfNoMatchingDirectory is being reset with a new list from grep. I added push so that @pdfNoMatchingDirectory instead accumulates all the elements you're looking for. That may not be what you're after, so you might remove the push again.

    You know, I keep seeing the word DataBase in your variables. It would probably be more efficient to use your SQL database's SQL engine to perform the set-symmetric-difference task.


    Dave

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      Thank you. I actually was getting ready to post my final solution. I used a cpan module that included the exact operation I was looking for. 
      

#!/usr/bin/perl -w
use strict;
use Array::Utils qw(:all);

my $boxEnd;
my $pathToDirectory;
my $pathToDatabase = "\\\\SHARESERVER\\DigiOfficeShare\\PerlDev\\Datab
+ase.txt";
my @contentsOfDataBase;
my @contentsOfDirectory;

print "First Box?", "\n";
chomp (my $boxBegining = <>);
print "Last Box?", "\n";
chomp ($boxEnd = <>);
print "\n", "Wait a minute while I look... Lazy...", "\n";

open my $databaseOutput, $pathToDatabase || die "\n", "Cannot find fil
+e.", "\n";
@contentsOfDataBase = <$databaseOutput>;
chomp @contentsOfDataBase;
close $databaseOutput;

while ($boxEnd >= $boxBegining) {
  my $pathToDirectory = "\\\\SHARESERVER\\DigiOfficeShare\\PerlDev\\Bo
+x $boxBegining";
  $boxBegining++;
  opendir(my $currentDirectory, $pathToDirectory) || die "\n", "You su
+re that exists, dummy?", "\n"; 
    while(readdir $currentDirectory) {
      chomp $_;
      push(@contentsOfDirectory, $_);
    }
  closedir $currentDirectory;

}

@contentsOfDirectory = grep (!/^\./, @contentsOfDirectory);
my @minus = array_minus( @contentsOfDirectory, @contentsOfDataBase );
my @minus2 = array_minus( @contentsOfDataBase, @contentsOfDirectory);

print "\n", "These files have PDFs and no database entries:", "\n", "\
+n", "\n";

foreach (@minus){
  print "\n", "$_ ", "\n";

}

print "\n", "These files have databse entries and no PDFs:", "\n";

foreach (@minus2){
  print "\n", "$_ ", "\n";

}

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