Re: Converting an Array Reference into an Array

A quick look with B::Terse (hey, I learned a new trick, I'm gonna use it :) ) at this:

my $aryref=[ qw(one two) ];
my @array=@$aryref;
my @arraytwo=qw(one two);
[download]

Shows this as a result:

LISTOP (0x8115698) leave [1]
    OP (0x8120b78) enter
    COP (0x8115658) nextstate
    BINOP (0x8115630) sassign
        UNOP (0x81795e0) srefgen
            UNOP (0x8120cd8) null [141]
                LISTOP (0x8120340) anonlist
                    OP (0x8120cb8) pushmark
                    SVOP (0x811a068) const  PV (0x811d8e4) "one"
                    SVOP (0x81203c0) const  PV (0x811d8d8) "two"
        OP (0x814db90) padsv [1]
    COP (0x81157d0) nextstate
    BINOP (0x8115770) aassign [4]
        UNOP (0x8115728) null [141]
            OP (0x8115750) pushmark
            UNOP (0x81156c0) rv2av [3]
                OP (0x8179600) padsv [1]
        UNOP (0x81156e0) null [141]
            OP (0x8115708) pushmark
            OP (0x81795c0) padav [2]
    COP (0x8120b38) nextstate
    BINOP (0x8120b10) aassign [6]
        UNOP (0x8120a80) null [141]
            OP (0x8120aa8) pushmark
            SVOP (0x8120a40) const  PV (0x811d908) "one"
            SVOP (0x8120a60) const  PV (0x811d8f0) "two"
        UNOP (0x8120ac8) null [141]
            OP (0x8120af0) pushmark
            OP (0x8115810) padav [5]
cloning.pl syntax OK
[download]

In other words, the @array=@$aryref does not copy the array members, it just sets up @array to point to the data pointed to by $aryref (and increases said data's refcount). Perl does the right thing here. So, you should not expect a performance penalty for this. You should still have some penalty (notably, pointing the new array's members to the SV's), but not the same as creating a full blown array from the ground up. Ah well, rv2av is apparently a full blown copy. Never mind my blabbering. Thanks chromatic and PodMaster.

However, I would try and get used to the 'ugly syntax' of references and dereferencing them - they are among the most powerful features of Perl and are the only way of building complex data structures. You will need them :)

Update: Stopped lying. :)

CU
Robartes-

Comment on Re: Converting an Array Reference into an Array Select or Download Code

Replies are listed 'Best First'.

Re: Re: Converting an Array Reference into an Array
by chromatic (Archbishop) on Mar 12, 2003 at 08:01 UTC

This is incorrect. rv2av dereferences an array reference. Search for pp_rv2av in pp_hot.c.

[reply]
[d/l]
[select]

Re: Re: Converting an Array Reference into an Array
by PodMaster (Abbot) on Mar 12, 2003 at 08:01 UTC

my $coy = [ 1, 2];
my @coy = @$coy;
$coy[1] = 666;
use Data::Dumper;
die Dumper( $coy, \@coy );
__END__
$VAR1 = [
          1,
          2
        ];
$VAR2 = [
          1,
          666
        ];
[download]

copy on write

MJD says you can't just make shit up and expect the computer to know what you mean, retardo!
I run a Win32 PPM repository for perl 5.6x+5.8x. I take requests.
** The Third rule of perl club is a statement of fact: pod is sexy.

[reply]
[d/l]