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Postings from April 2018
On Thu, Apr 19, 2018 at 06:37:26PM -0700, L A Walsh wrote:
> Dan Book via RT wrote:
> > On Thu, Apr 19, 2018 at 6:09 PM, L A Walsh <perl-diddler@tlinx.org> wrote:
> > ...
> >
> > > The manpage shows:
> > > Functions for real @ARRAYs
> > > "each", "keys", "pop", "push", "shift", "splice", "unshift",
> > > "values"
> > >
> > > Functions for real %HASHes
> > > "delete", "each", "exists", "keys", "values"
> > >
> >
> > each, keys, and values work on both arrays and hashes. As does exists and
> > delete, technically.
> >
> > -Dan
> >
> Yes...for dereferencing to work in this case, the scalar would have to
> hold either an ARRAY or HASH reference. It really makes no sense to try
> to use "each", "keys" nor "values" on a a scalar that has value 'undef'.
> It would make no sense and would (should) generate an error as it does
> now.
But when you have a scalar reference which is overloaded, perl can't know
what overload method to call in those cases. For example:
use overload
'@{}' => sub { print "array deref\n" ; return \@real_a },
'%{}' => sub { print "hash deref\n" ; return \%real_h },
;
my $r = bless [];
push $r, 3; # prints "array derdef", modifies @real_a
$r->{foo} = 'bar'; # prints "hash derdef", modifies %real_h
@k = keys $r; # what overload method does this call?
What should perl do in the last case?
--
The optimist believes that he lives in the best of all possible worlds.
As does the pessimist.
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