OK. I downloaded it and duplicated the problem. The behavior is
clearly both a bug and not as documented. -- jeffrey
On 01/07/2014 11:43 AM, Ruslan Zakirov wrote:
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 $rec->value;
sub dummy {
shift;
return [@_];
}
On Tue, Jan 7, 2014 at 9:52 PM, Jeffrey Kegler
<[email protected]
<mailto:[email protected]>> wrote:
Things do look problematic here.
Could you create a small example duplicating the failure? An
advantage of these is that it clarifies for me exactly what you
expect to happen.
A complication here is that in addition to Perl undef's, I
introduced "whatever" variables to Marpa. These are allowed to
have any value -- presumably they'd be for cases where you ignore
the value. That is, an 'undefined' value must be undef, but a
'whatever' value can be undef one time, 42 the next, and "hello"
the next.
"Whatever" values were intended to save stack operations. Marpa's
NAIF did these via callback, so every stack op save was a big
win. When a whatever value needs to be put on the stack, it's a
no-op, whereas when an Perl undef needs to be put on the stack,
it's a callback -- a vast difference in resource.
With the SLIF, I implement callbacks more cheaply, and future
changes may reduce this cost further. This means the time and
trouble to track whatever values is probably not worth it.
"Whatever" values may be deprecated in Libmarpa. I think I kept
them out of the Marpa::R2 documentation, so this deprecation would
only be relevant at the Libmarpa and THIF levels.
-- jeffrey
On 01/07/2014 02:12 AM, Ruslan Zakirov wrote:
Hi,
I know that at some point ignorable products was optimized and
resulted in undefined (=== random) values in actions, but hell
let me do what I mean.
Doc says pass reference to value and I'm passing it reference to
undef.
It worked just fine at some point but then it was broken.
Responsible change is
dae6a5697dec6a5bb039418e3329db615e535dec and the following part
in particular:
- push @{$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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