in reply to Sort Hash of Hash numerically

Super Search where title contains all of "sort", "hash", "of": 
use warnings;
use strict;

my (%HoH) = (
    "Smith" => {
        "house_type" => 'colonial',
        "head_count" => '5',
    },
    "Jones" => {
        "house_type" => 'cape',
        "head_count" => '3',
    },
);

for (reverse sort { $HoH{$a}{head_count} <=> $HoH{$b}{head_count} } ke
+ys %HoH) {
    print "$_ House Type: $HoH{$_}{house_type} Head Count: $HoH{$_}{he
+ad_count}\n";
}

__END__

Smith House Type: colonial Head Count: 5
Jones House Type: cape Head Count: 3

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Re^2: Sort Hash of Hash numerically
by duelafn (Parson) on Jun 13, 2011 at 14:33 UTC

    Is reverse sort optimized away (it would be cool if it swapped the meaning of $a and $b) or do you really mean:

    for (sort { $HoH{$b}{head_count} <=> $HoH{$a}{head_count} } keys %HoH)
+ {
    print "$_ House Type: $HoH{$_}{house_type} Head Count: $HoH{$_}{he
+ad_count}\n";
}

    [download]

    Update: toolic++. I went searching for the definition of "newer perls" and found that this optimization has been around for some time. From perl586delta:

    reverse sort ... is now optimized to sort in reverse, avoiding the generation of a temporary intermediate list.

    for (reverse @foo) now iterates in reverse, avoiding the generation of a temporary reversed list.

    Good Day,
        Dean

[reply]
[d/l]
[select]
      I really meant to use reverse. According to Perl::Critic::Policy::BuiltinFunctions::ProhibitReverseSortBlock
      Conway says that it is much clearer to use reverse than to flip $a and $b around in a sort block. He also suggests that, in newer perls, reverse is specifically looked for and optimized, and in the case of a simple reversed string sort, using reverse with a sort with no block is faster even in old perls.
[reply]
Re^2: Sort Hash of Hash numerically
by Anonymous Monk on Jun 13, 2011 at 14:41 UTC
    Awesome, that did it. Thanks!
[reply]

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