Re^3: Does @{ } copy arrays?

Interesting! That's the kind of answer I was hoping someone would post. For anyone who's keeping score, here's a benchmark and my results:

#!/usr/bin/perl

use strict;
use warnings;
use Benchmark qw(cmpthese);

my $i=0;
cmpthese(-10,
    {
        deref => sub {
            my $aryptr = [qw(Once upon a time in a galaxy far far away
+)];
            if ( @{ $aryptr } )
            {
                $i=1;
            }
            $aryptr = [];
            if ( @{ $aryptr } )
            {
                $i=-1;
            }
        },
        arylen => sub {
            my $aryptr = [qw(Once upon a time in a galaxy far far away
+)];
            if ( $#{ $aryptr } >= 0 )
            {
                $i=1;
            }
            $aryptr = [];
            if ( $#{ $aryptr } >= 0 )
            {
                $i=-1;
            }
        },
    }
);

__END__
           Rate arylen  deref
arylen  95903/s     --   -28%
deref  132418/s    38%     --
[download]

print pack("A25",pack("V*",map{1919242272+$_}(34481450,-49737472,6228,0,-285028276,6979,-1380265972)))

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Re^4: Does @{ } copy arrays? by ikegami (Patriarch) on Oct 23, 2009 at 20:57 UTC
The point is that `$#a` should be faster than `@a-1`. That's not what you are testing. You have have an extra operation in your $#a test instead of having one less. `#!/usr/bin/perl use strict; use warnings; use Benchmark qw(cmpthese); our @a = qw( Once upon a time in a galaxy far far away ); cmpthese(-3, { cnt_minus_1 => 'my $x = @a-1;', last_idx => 'my $x = $#a;', });` [download] `Rate last_idx cnt_minus_1 last_idx 3225597/s -- -25% cnt_minus_1 4308243/s 34% --` [download]	[reply] [d/l] [select]

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Re^4: Does @{ } copy arrays?
by ikegami (Patriarch) on Oct 23, 2009 at 20:57 UTC

The point is that $#a should be faster than @a-1. That's not what you are testing. You have have an extra operation in your $#a test instead of having one less.

#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw(cmpthese);

our @a = qw( Once upon a time in a galaxy far far away );

cmpthese(-3, {
    cnt_minus_1 => 'my $x = @a-1;',
    last_idx    => 'my $x = $#a;',
});
[download]

                 Rate    last_idx cnt_minus_1
last_idx    3225597/s          --        -25%
cnt_minus_1 4308243/s         34%          --
[download]

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