perl – 根据插入顺序迭代哈希？

foreach my $val (keys %hash) {
     ...
 }

默认情况下,Perl 5中的哈希是无序的.您可以使用 tie和 Tie::IxHash来覆盖此行为.不过要警告,有一个表现打击和其他考虑(例如,这个订单不会保留在副本中).

#!/usr/bin/perl

use Strict;
use warnings;

use Tie::IxHash;

tie my %hash,"Tie::IxHash"
    or die "could not tie %hash";

$hash{onE}   = 1;
$hash{two}   = 2;
$hash{threE} = 3;

for my $k (keys %hash) {
    print "$k $hash{$k}\n";
}

更好的选择可能是使用数组或散列哈希：

#!/usr/bin/perl

use Strict;
use warnings;

my %hash;
$hash{onE}   = { data => 1,order => 1 };
$hash{threE} = { data => 3,order => 2 };
$hash{two}   = { data => 2,order => 3 };

for my $k (sort { $hash{$a}{order} <=> $hash{$b}{order} } keys %hash) {
    print "$k $hash{$k}{data}\n";
}

至于表现,以下是一个基准的结果：

IndexedOO: a,b,c,d,e,f
Hashordered: a,f
IxHashOO: a,f
hash: f,a,d
hoh_pis: a,f
IxHash: a,f
hoh: a,f
Indexed: a,f
              Rate IxHash  hoh Indexed IxHashOO IndexedOO hoh_pis Hashordered hash
IxHash       261/s     -- -18%    -26%     -48%      -54%    -57%        -66% -80%
hoh          316/s    21%   --    -10%     -37%      -44%    -48%        -59% -75%
Indexed      353/s    35%  12%      --     -29%      -38%    -42%        -55% -72%
IxHashOO     499/s    91%  58%     41%       --      -12%    -18%        -36% -61%
IndexedOO    569/s   118%  80%     61%      14%        --     -7%        -27% -56%
hoh_pis      611/s   134%  93%     73%      22%        7%      --        -21% -52%
Hashordered  778/s   198% 146%    120%      56%       37%     27%          -- -39%
hash        1279/s   391% 305%    262%     156%      125%    109%         64%   --

从这里我们可以看到,如果您不需要使用Hash :: ordered就可以像普通哈希(即绑定的哈希)那样运行.

这是基准：

#!/usr/bin/perl

use Strict;
use warnings;

use Tie::IxHash;
use Tie::Hash::Indexed;
use Hash::ordered;
use Benchmark;

#this is O(n) instead of O(n log n) or worse
sub perfect_insert_sort {
    my $h = shift;
    my @k;
    for my $k (keys %$h) {
        $k[$h->{$k}{order}] = $k;
    }
    return @k;
}

my @keys = qw/a b c d e f/;
my %subs = (
    hash => sub {
        my $i;
        my %h = map { $_ => $i++ } @keys;
        return join ",",keys %h;
    },hoh => sub {
        my $i;
        my $order;
        my %h = map {
            $_ => { data => $i++,order => $order++ }
        } @keys;
        return join ",sort { $h{$a}{order} <=> $h{$b}{order} }
            keys %h;
    },hoh_pis => sub {
        my $i;
        my $order;
        my %h = map {
            $_ => { data => $i++,perfect_insert_sort \%h;
    },IxHash => sub {
        my $i;
        tie my %h,"Tie::IxHash";
        %h = map { $_ => $i++ } @keys;
        return join ",Indexed => sub {
        my $i;
        tie my %h,"Tie::Hash::Indexed";
        %h = map { $_ => $i++ } @keys;
        return join ",IxHashOO => sub {
        my $i;
        my $o = tie my %h,"Tie::IxHash",map { $_ => $i++ } @keys;
        return join ",$o->Keys;
    },IndexedOO => sub {
        my $i;
        my $o = tie my %h,"Tie::Hash::Indexed",map { $_ => $i++ } @keys;
        my @k = my $k = $o->FIRSTKEY;
        while ($k = $o->NEXTKEY($k)) {
            push @k,$k;
        }
        return join ",@k;
    },Hashordered => sub {
    my $i;
        my $oh = Hash::ordered->new( map { $_ => $i++ } @keys );
        return join ",$oh->keys;
    },);

for my $sub (keys %subs) {
    print "$sub: ",$subs{$sub}(),"\n";
}

@keys = 1 .. 1_000;
Benchmark::cmpthese -2,\%subs;