greping thru a hash of arrays

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

Not sure what I'm doing wrong here. I've used grep many times looking for text within an array. For example,

@tmp = grep /${text}/,@array_of_something
[download]

So I decide to create a hash of arrays. The individual elements I can "see" -- for example, $tbl{"key"}[0] is correct. So can't I grep thru this too? See code below.

perl -de '
  foreach $i (map {glob} "COMFILE1.2008*") {
    open(IN,$i);
    chomp(@tmp = (<IN>));
    $tbl{$i} = [ @tmp ] ;
    close(IN);
  }

  open(IN,"dw_renewals.txt");
  while(<IN>) {
    chomp;
    foreach $i (sort keys %tbl) {
      @tmp = [ @tbl{$i} ];
      if (grep /$_/, [ @tbl{$i} ] ) {
        print "$_ in $i $y\n";
      }
    }
  }
'
[download]

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Re: greping thru a hash of arrays by pc88mxer (Vicar) on May 20, 2008 at 20:58 UTC
You can grep through it, but you have an error in how you are accessing the array ref. You need to do it like this: `if (grep /$_/, @{$tbl{$i}} ) {` [download] Update: Removed square brackets which I didn't see the first time around. Another problem, though, is that `$_` gets assigned to in the grep operation, and that the match operator implicitly operates on `$_`. Thus, `grep /$_/, ...` is equivalent to `grep { $_ =~ /$_/ } (...)` which is probably not what you want. Instead, try this: `while (my $line = <IN>) { ... for my $i (...) { if (grep /$line/, @{$tbl{$i}}) { ... } } }` [download]	[reply] [d/l] [select]
Re^2: greping thru a hash of arrays by pglenski (Beadle) on May 20, 2008 at 21:10 UTC
Thanks, that works. But why?	[reply]
Re^3: greping thru a hash of arrays by linuxer (Curate) on May 20, 2008 at 21:15 UTC
`grep /$_/, [ @{$tbl{$i}} ]` [download] means: Dereference the array-Ref in $tbl{$i}, make a reference to an anonymous array ( [ ] ) from the resulting list and grep through a list with a single item: the single reference to the anonymous array. `@tbl{$i}` is btw. wrong, see this example : `$perl perl use strict; use warnings; my %hash; $hash{a} = [ 1,2 ]; print "@hash{a}", $/; Scalar value @hash{a} better written as $hash{a} at - line 7.` [download] edit: several updates/corrections due to some misleading thoughts while typing too fast	[reply] [d/l] [select]
Re^3: greping thru a hash of arrays by pc88mxer (Vicar) on May 20, 2008 at 21:19 UTC
There were a few errors. As linuxer pointed out, the second argument to `grep` should not be an array-ref. The second through last arguments are the list of items to grep through. Also, instead of `@tbl{$i}` you want to use `@{$tbl{$i}}`.	[reply] [d/l] [select]
Re: greping thru a hash of arrays by johngg (Canon) on May 20, 2008 at 22:16 UTC
`foreach $i (map {glob} "COMFILE1.2008")`* You don't need to wrap a map around your glob. `$ ls copy1 copy2 file1 file2 file3 $ perl -le 'foreach $i ( glob q{c*} ) { print $i }' copy1 copy2 $` [download] Cheers, JohnGG	[reply] [d/l] [select]