use strict; use warnings; use 5.010;
use Marpa::R2;
use Marpa::R2::Grammar;
use MarpaX::Repa::Actions;
my $grammar = Marpa::R2::Grammar->new( {
start => 'start',
actions => 'main',
default_action => 'dummy',
rules => [
[ start => [qw/x y/] ],
],
} );
$grammar->precompute;
my $rec = Marpa::R2::Recognizer->new( { grammar => $grammar } );
$rec->alternative('x',\undef, 1);
$rec->earleme_complete;
$rec->alternative('y',\"some", 1);
$rec->earleme_complete;
use Data::Dumper;
say Dumper $rec->value;
sub dummy {
shift;
return [@_];
}
On Tue, Jan 7, 2014 at 9:52 PM, Jeffrey Kegler <
[email protected]> wrote:
> Things do look problematic here.
>
> Could you create a small example duplicating the failure? An advantage of
> these is that it clarifies for me exactly what you expect to happen.
>
> A complication here is that in addition to Perl undef's, I introduced
> "whatever" variables to Marpa. These are allowed to have any value --
> presumably they'd be for cases where you ignore the value. That is, an
> 'undefined' value must be undef, but a 'whatever' value can be undef one
> time, 42 the next, and "hello" the next.
>
> "Whatever" values were intended to save stack operations. Marpa's NAIF
> did these via callback, so every stack op save was a big win. When a
> whatever value needs to be put on the stack, it's a no-op, whereas when an
> Perl undef needs to be put on the stack, it's a callback -- a vast
> difference in resource.
>
> With the SLIF, I implement callbacks more cheaply, and future changes may
> reduce this cost further. This means the time and trouble to track
> whatever values is probably not worth it. "Whatever" values may be
> deprecated in Libmarpa. I think I kept them out of the Marpa::R2
> documentation, so this deprecation would only be relevant at the Libmarpa
> and THIF levels.
>
> -- jeffrey
>
> On 01/07/2014 02:12 AM, Ruslan Zakirov wrote:
>
> Hi,
>
> I know that at some point ignorable products was optimized and resulted
> in undefined (=== random) values in actions, but hell let me do what I mean.
> Doc says pass reference to value and I'm passing it reference to undef.
>
> It worked just fine at some point but then it was broken.
>
> Responsible change is
> dae6a5697dec6a5bb039418e3329db615e535dec and the following part in
> particular:
>
> - push @{$token_values}, ${$value_ref};
> + my $value = ${$value_ref};
> + last SET_VALUE_IX if not defined $value;
> + push @{$token_values}, $value;
>
> I don't see how it is related to whole change.
>
> Also, I see that "# Position 1 is reserved for undef" in $token_values
> then this probably just a bug and the following should be applied:
>
> diff --git a/cpan/lib/Marpa/R2/Recognizer.pm
> b/cpan/lib/Marpa/R2/Recognizer.pm
> index d700590..219e839 100644
> --- a/cpan/lib/Marpa/R2/Recognizer.pm
> +++ b/cpan/lib/Marpa/R2/Recognizer.pm
> @@ -669,10 +669,9 @@ sub Marpa::R2::Recognizer::alternative {
> {
> Marpa::R2::exception('alternative(): value must be undef or
> ref');
> } ## end if ( $ref_type ne 'SCALAR' and $ref_type ne 'REF' and...)
> + last SET_VALUE_IX if not defined $$value_ref;
> $value_ix = scalar @{$token_values};
> - my $value = ${$value_ref};
> - last SET_VALUE_IX if not defined $value;
> - push @{$token_values}, $value;
> + push @{$token_values}, $$value_ref;
> } ## end SET_VALUE_IX:
> $length //= 1;
>
> --
> Best regards, Ruslan.
> --
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--
Best regards, Ruslan.
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