Re^2: hash of hashes

Why on earth would you want to do that?

You'd want to do that in perl if the original input contains duplicates and you only want to show unique license plate numbers. Since perl doesn't have a built-in concept of a (uniqe) set hashes are the natural structure to use.

To the OP: note that i use sort here, but that's just because I presume you'd want the output to be predictable.

$plates{$lets}{$number} =1;  # or $plates{$lets}{$number}++ if you wan
+t to count
# and
for my $let (sort keys %plates) {
  print "$let ",join(", ",sort keys %{$plates{$let}}),"\n";
}
[download]

Updated: removed map() - code should now be correct

"What should it profit a man, if he should win a flame war, yet lose his cool?"

Comment on Re^2: hash of hashes Download Code

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Re^3: hash of hashes by volcan (Novice) on Mar 23, 2007 at 22:08 UTC
Hi Joost, You are correct that I am using a hash of hashes because of duplicates. The program will be reading multiple files, many of which will contain the same license plate. I'm going to try your code now and will report back shortly. Many thanks! 8^}	[reply]
Re^3: hash of hashes by Anno (Deacon) on Mar 24, 2007 at 08:05 UTC
Well, the OP said proper output would look like: `ABC 123, 334, 442 FTE 442 HHR 443 NTR 554, 554` [download] Note the last line, which shows a duplicate number. I have seen the OPs reply that confirms that duplicates are indeed unwanted. The sample output seemed to indicate the opposite. Anno	[reply] [d/l]
Re^4: hash of hashes by volcan (Novice) on Mar 25, 2007 at 19:59 UTC
Putting a duplicate in there was a mistake, so you were quite right in thinking a hash of a hash would be a bad idea since it looked like duplicates were allowed. Thanks for your help.	[reply]