sorting hash by value when value is an array ref

beachguy82 has asked for the wisdom of the Perl Monks concerning the following question:

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Re: sorting hash by value when value is an array ref by jdporter (Paladin) on Nov 16, 2004 at 02:28 UTC
`@sorted_keys = sort { $foo{$a}[1] cmp $foo{$b}[1] } keys %foo;` [download]	[reply] [d/l]
Re: sorting hash by value when value is an array ref by Zaxo (Archbishop) on Nov 16, 2004 at 02:31 UTC
Here you go, `my @sorted_keys = sort { $foo{$a}[1] <=> $foo{$b}[1] } keys %foo;` [download] (assuming numeric comparison is appropriate) [ Nope, alpha sort is correct, use `cmp` instead of `<=>`. I don't know how I missed that part of the question. ] After Compline, Zaxo	[reply] [d/l]
Re^2: sorting hash by value when value is an array ref by beachguy82 (Novice) on Nov 16, 2004 at 02:42 UTC
I must say, I'm amazed by the quick response. This is my first questoin on this board. But back to the question. I had already been trying that bit of code the two of you posted and it doesn't seem to work. My list of keys still isn't sorted by the date. Any clue why? I also tried cmp and <=>.	[reply]
Re^3: sorting hash by value when value is an array ref by ikegami (Patriarch) on Nov 16, 2004 at 07:24 UTC
Update: Sorry, I see you've already done that. The code jdporter and Zaxo provided will indeed do what you ask. There's either an error in your description, or an error in the input you're using. Why don't you provide us a runnable snippet (complete with inputs) so we can continue to help you.	[reply]
Re^2: sorting hash by value when value is an array ref by pg (Canon) on Nov 16, 2004 at 02:55 UTC
cmp is what he is looking for, this will not fully work, as the element is a string not a number. jdporter got it right. Update: Zaxo already had this fixed before he saw my reply.	[reply]
Re: sorting hash by value when value is an array ref by ysth (Canon) on Nov 16, 2004 at 02:46 UTC
Hmm. Since what should have worked didn't, can you show at least part of the output of: `use Data::Dumper; print Dumper \%foo;` [download] and also copy and paste the exact code you are trying?	[reply] [d/l]
Re^2: sorting hash by value when value is an array ref by beachguy82 (Novice) on Nov 16, 2004 at 02:59 UTC
foreach $homework (@homeworks) { $query = "SELECT PointValue,DueDate FROM Homework WHERE ClassID = +\'$courseID\' AND SectionID = \'$sectionID\' AND InstructorID = $ins +tructorID AND HomeworkName = \'$homework\'"; $statementHandle = $databaseHandle -> prepare($query); $statementHandle -> execute(); while(@rowArray = $statementHandle -> fetchrow_array()) { $homeworkHash{$homework} = [$rowArray[0],$rowArray[1]] +; } } # now the sorting my @sorted = sort { $homeworkHash{$a}[1] cmp $homeworkHash{$b}[1] } ke +ys %homeworkHash; # I then pass the @sorted to a template under the name homeworks and i +n the template I use this to print out the hash. [% FOREACH key IN homeworks %] <th valign="bottom" class="Homework"><span id="points">[% key +%]</span><br>[% homework.$key.0 %]<br>[% homework.$key.1 %]</th> [% END %] [download] This doesn't print out a thing in the template. It is as if the @sorted in empty.	[reply] [d/l]
Re^3: sorting hash by value when value is an array ref by jdporter (Paladin) on Nov 16, 2004 at 03:06 UTC
Well, I don't know what all that non-Perl junk is... but I'm inclined to guess that `[% FOREACH key IN homeworks %]` is iterating over the keys in some other order, and that you're throwing away the result of the sort you so carefully set up. Do you know a way to set the key for iteration based on the contents of `@sorted` ?	[reply] [d/l] [select]
Re^4: sorting hash by value when value is an array ref by beachguy82 (Novice) on Nov 16, 2004 at 03:15 UTC
Re^5: sorting hash by value when value is an array ref by beachguy82 (Novice) on Nov 16, 2004 at 03:23 UTC
Some notes below your chosen depth have not been shown here
Re: sorting hash by value when value is an array ref by TedPride (Priest) on Nov 16, 2004 at 14:03 UTC
`for (sort {$foo{$a}[1] cmp $foo{$b}[1] or $a cmp $b} keys %foo) { print "$_ -> ['" . $foo{$_}[0] . "', '" . $foo{$_}[1] . "']\n"; }` [download] You have to have two comparisons, otherwise identical array values will result in keys being displayed out of order. I've included a print line to show how keys and values are accessed after the sort.	[reply] [d/l]