Odd number of elements in anon hash

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

Hi,

I have an array of hashes of arrays of arrays... I want to sort the arrays in the array of arrays in a specific hash according to the first element in each array.

This seems to work:

my @sorted =  sort { $$a[0] <=> $$b[0] } @{$simulations[$simulation_in
+dex]->{"SPECIAL"} };
$simulations[$simulation_index]->{"SPECIAL"} =\@sorted;
[download]

but the following, which for me seems the same (except without the temporary @sorted) - returns "Odd number of elements in anonymous hash at..."

$simulations[$simulation_index]->{"SPECIAL"} = \{sort {$$a[0] <=> $$b[
+0] } @{$simulations[$simulation_index]->"SPECIAL"} }};
[download]

Comment on Odd number of elements in anon hash Select or Download Code

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Re: Odd number of elements in anon hash by almut (Canon) on Jun 01, 2010 at 13:14 UTC
For one, you're missing a curly before `"SPECIAL"`. But I think you rather want `$simulations[$simulation_index]->{"SPECIAL"} = [ sort {$$a[0] <=> $$b[ +0] } @{$simulations[$simulation_index]->{"SPECIAL"} } ];` [download] i.e., the anonymous array `[ ... ]` would correspond to your original `\@sorted`. What you have is a reference to a hashref (`\{ ... }`), where the anonymous hash complains when initialized with an odd number of elements from the sort results.	[reply] [d/l] [select]
Re^2: Odd number of elements in anon hash by roibrodo (Sexton) on Jun 01, 2010 at 13:32 UTC
Thanks! I guess I'm not so familiar with the basics of "referencing" (I'm not even sure if that's the right name). so, when you use `[ ... ]` - does it return a reference to the enclosed an array? I think I was taught to use something like `\@{...}`. Does it mean the curly should be used only for hashes?	[reply] [d/l] [select]
Re^3: Odd number of elements in anon hash by almut (Canon) on Jun 01, 2010 at 13:38 UTC
`[ ... ]` returns a reference to an anonymous array. `{ ... }` returns a reference to an anonymous hash. In the appropriate syntactic context like assignment, that is. Curlies are used for various things, for example a block, or to group/disambiguate when dereferencing, like `@{ $obj->method_that_returns_an_arrayref() }`.	[reply] [d/l] [select]
Re^3: Odd number of elements in anon hash by GrandFather (Saint) on Jun 01, 2010 at 23:42 UTC
You may find References quick reference helps. True laziness is hard work	[reply]
Re: Odd number of elements in anon hash by jethro (Monsignor) on Jun 01, 2010 at 13:11 UTC
`[$simulation_index]->"SPECIAL"} [$simulation_index]->{"SPECIAL"} ^` [download]	[reply] [d/l]