I'm not suggesting that you actually use this, but the following is a simple implementation of the :zero (here :ZeroDefault) attribute. It's intended to show you that what you would like to have is quite easy to implement in pure Perl without changing the interpreter at all or writing a single line of XS/C. All the usual attribute-gotchas apply. All the usual tie() gotchas apply, too. (Slowness, for example.)

#!/usr/bin/perl
use 5.006;
use strict;
use warnings;

package Attribute::Array::Zeroes;
use Tie::Array;
use base 'Tie::StdArray';
use Attribute::Handlers autotie => {
  '__CALLER__::ZeroDefault' => 'Attribute::Array::Zeroes'
};

sub FETCH {
  my $return = $_[0]->[$_[1]];
  return 0 if not defined $return;
  $return;
}

package main;
#use Attribute::Array::Zeroes;

my @x : ZeroDefault;

print "This is zero, not undef: $x[4]\n";

$x[5] = 1;
print "This, too: $x[0] and even this: $x[6]. This isn't: $x[5]\n";

[download]

Of course, this is just a hack and I haven't tested it thoroughly.

Cheers,
Steffen

In reply to Re: A pair of "mathematical" attributes for arrays? by tsee
in thread A pair of "mathematical" attributes for arrays? by blazar

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