Ron,
Execute the following and say what's your feeling -;
#!env perl
use Marpa::R2;
my $grammar = ":start ::= test\ntest ::= 'x'\n";
my $input = 'x';
my %hash = (grammar => Marpa::R2::Scanless::G->new( { source => \$grammar
}) );
Marpa::R2::Scanless::R->new($hashp);
Marpa::R2::Scanless::R->new($hashp);
Le samedi 21 décembre 2013 20:14:31 UTC+1, rns a écrit :
>
> The first thing that came to mind was
>
>
> my $self = shift;
>
>
> Not sure if this fully applies here though.
>
>
> On Sat, Dec 21, 2013 at 7:48 PM, Jeffrey Kegler <
> [email protected] <javascript:>> wrote:
>
>> I am forwarding the comment below from Jean-Damien into the group for
>> feedback.
>>
>> My sense of the matter is that Perl methods using named argument hashes
>> are entitled to consume them in the process. That means that after
>>
>> $hashp = { ... repeatedly useful things };
>> my $recognizer = Marpa::R2::Scanless::R->new($hashp);
>>
>> reuse of $hashp cannot be relied on to work, because Marpa::R2's
>> methods may consume the hash pointed to by $hashp. (Marpa often needs to
>> process its arguments in stages, and finds its useful to track those
>> already processed by deleting elements.) Note that the user can get around
>> this by copying the hash, which moves the overhead for these unusual
>> argument manipulations from application to user, which to my mind is a good
>> thing.
>>
>> Anyone else have a sense of this matter? Simply stating your personal
>> preference is OK, but I'll give greater weight to evidence of best
>> practices, traditions, etc.
>>
>> -- jeffrey
>>
>> -------- Original Message -------- Subject: Re: [Marpa--R2] Work on
>> multiple lexers: t+, but noisy (f9d2b50) Date: Sat, 21 Dec 2013
>> 08:00:51 -0800 From: jddurand <[email protected]> <javascript:>
>> Reply-To:
>> jeffreykegler/Marpa--R2
>> <reply+c-4923070-46b158946abddd67de008743caef1226be890a0d-173...@reply.github.com><javascript:>
>> To:
>> jeffreykegler/Marpa--R2 <[email protected]> <javascript:>
>>
>>
>> Playing with user's arguments has side-effects. The line:
>>
>> delete $args[0]->{grammar};
>>
>> in particular is disastrous for callers that are storing a reference to a
>> precompiled grammar, not having a reference to it anywhere else in this
>> program than in the hash given in input to R->new().
>>
>> For example, if the grammar is precompiled and referenced only in a hash
>> used as a R->new() parameter, then Scanless will happily destroy the
>> precompiled grammar.
>>
>> Example with the perl6 advent calendar where I modified the arguments to
>> R->new(). Look to $hashp in the source code at
>> https://gist.github.com/jddurand/8071223
>>
>> Output is:
>>
>> 2♥ 5♥ 7♦ 8♣ 9♠ : OK
>> 'grammar' name argument to scanless_r->new() is undefined
>> It should be a ref to Marpa::R2::Scanless::G
>> Marpa::R2 exception at /tmp/perl6advent.day18.with.marpa.pl line 22.
>>
>> —
>> Reply to this email directly or view it on
>> GitHub<https://github.com/jeffreykegler/Marpa--R2/commit/f9d2b50d9226c918738e9760c64c2893d6d13cc8#commitcomment-4923070>
>> .
>>
>>
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