Re: Re: Perl Optimization


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Re: Re: Perl Optimization

by Cybercosis (Monk)

on Jun 01, 2001 at 20:29 UTC ( [id://84982]=note: print w/replies, xml )

Need Help??

in reply to Re: Perl Optimization
in thread Perl Optimization

foreach my $obj (%{$href})
# This dereference ^ causes a deep copy to be made
actually, this is more accurate:

foreach my $obj (%{$href})
     #here ^ is the copy
[download]

If you check the ref()-iness of $obj, you'll find that there isn't any at all. The appropriate value is copied into $obj on each run of the loop. I'm not at all sure what it is you're trying to solve with this, but if you need access to the key/value pair without the big, horrendous copy, maybe something like this:

foreach my $key (keys %{$href})
{
  #do what you need with $key and $href->{$key}
}
[download]

Hope you find this useful!

~Cybercosis

nemo accipere quod non merere

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(tye)Re: Perl Optimization
by tye (Sage) on Jun 01, 2001 at 21:29 UTC

for and foreach make the argument an alias to (not a copy of) the values in the list.

Even if you copy a reference, you still get a reference, so I don't understand what you are trying to say.

my $href = {
  'x' => {
     'y' => {
         'z' => [ $xref, $yref, $zref ],
      },
     #'strange' => { ..... },
  },
  #'charm' => { .... },
};
for my $obj ( %$href ) {
    print "$obj: ",ref($obj),$/;
    my $copy= $obj;
    print "$copy: ",ref($copy),$/;
}
__END__
prints:
x:
x:
HASH(0x1a65030): HASH
HASH(0x1a65030): HASH
[download]

tye

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