, 'sub_name' ] syntax - marpa parser

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Message from discussion , 'sub_name' ] syntax
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Date: Wed, 26 Sep 2012 10:46:01 +0200
Message-ID: <CAE05vi7WEFYYc4zWdZL2=x_7nNtDNhYtxANSZJvdwPERQC0...@mail.gmail.com>
Subject: Re: [ lhs => [qw(symbol1 symbol2)], 'sub_name' ] syntax
From: Peter Stuifzand <peter.stuifz...@gmail.com>
To: marpa-parser@googlegroups.com
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In Perl you can write these things in two ways. The =3D> operator is
called a fat comma, which can be used (almost?) everywhere where a
comma can be used. But on top of that the fat comma also stringifies
the left side. That would mean that

     [ conditition =3D> [ qw(word) ] ]

is the same as

     [ 'conditition', [ qw(word) ] ]

See this manpage:
http://perldoc.perl.org/perlop.html#Comma-Operator and
http://en.wikipedia.org/wiki/Fat_comma


--
Peter Stuifzand | peterstuifzand.nl | @pstuifzand


On Wed, Sep 26, 2012 at 10:39 AM, rns <sor...@gmail.com> wrote:
>
>
> On Wednesday, September 26, 2012 11:33:42 AM UTC+3, Peter Stuifzand wrote=
:
>>
>> No, it is documented. I even included a link to the documentation.
>> Method (2) is used in MarpaX::Simple::Lexer example.
>
> MarpaX::Simple::Lexer uses [ condition =3D> [qw(word)] ], a key/value pai=
r in
> a array (rather than hash) that seems to be undocumented.
>
>>
>>
>> --
>> Peter Stuifzand | peterstuifzand.nl | @pstuifzand
>>
>>
>> On Wed, Sep 26, 2012 at 10:29 AM, rns <sor...@gmail.com> wrote:
>> > So it's undocumented, unofficial and thus needs to be avoided, thanks
>> > for
>> > explaining.
>> >
>> > On Wednesday, September 26, 2012 11:23:05 AM UTC+3, Peter Stuifzand
>> > wrote:
>> >>
>> >> There are two ways to specify rules:
>> >>
>> >> 1. Hashes (key/value pairs)
>> >>
>> >>     { lhs =3D> 'Term', rhs =3D> [qw/Term Add Term/], action =3D> 'do_=
add' }
>> >>
>> >>
>> >> 2. Arrays with short form syntax.
>> >>
>> >> https://metacpan.org/module/Marpa::R2::Grammar#Rule-descriptors-as-ar=
rays
>> >>
>> >>     [ 'Term', [qw/Term Add Term/], 'do_add' ]
>> >>
>> >> So that would be:
>> >>
>> >>    [ lhs, rhs, action ]
>> >>
>> >> where both rhs and action are optional. The rhs part should be an
>> >> array ref. You can't include more key/value type options in this
>> >> syntax. If you want that, you have to use the first method.
>> >>
>> >> --
>> >> Peter Stuifzand | peterstuifzand.nl | @pstuifzand
>> >>
>> >>
>> >> On Wed, Sep 26, 2012 at 10:11 AM, rns <sor...@gmail.com> wrote:
>> >> > Is _subj_ (used, e.g., in [1] Marpa-Simple-Lexer [1]) official?
>> >> >
>> >> > It worked for me in Marpa::R2 but will it be supported? I've found
>> >> > nothing
>> >> > about it in the R2's doc so it's probably not.
>> >> >
>> >> > A list of key/value pairs, e.g. [ lhs =3D> [qw(symbol1 symbol2)],
>> >> > action
>> >> > =3D>
>> >> > 'sub_name' ] doesn't work in R2 and probably shouldn't.
>> >> >
>> >> > I kind of like the terseness.
>> >> >
>> >> > [1]
>> >> >>
>> >> >>         [ condition =3D> [qw(word)] ],
>> >> >>         [ condition =3D> [qw(quoted)] ],
>> >> >>         [ condition =3D> [qw(OPEN-PAREN SPACE? query SPACE?
>> >> >> CLOSE-PAREN)]
>> >> >> ],
>> >> >>         [ condition =3D> [qw(NOT condition)] ],
>> >> >>
>> >> >>         [ 'SPACE?' =3D> [] ],
>> >> >>         [ 'SPACE?' =3D> [qw(SPACE)] ],
>> >> >
>> >> > =E2=80=94
>> >> >
>> >> > https://github.com/ruz/Marpa-Simple-Lexer/blob/master/examples/syno=
psis.pl
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