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.\"
.IX Title "Pegex::Grammar 3"
.TH Pegex::Grammar 3 2024-09-01 "perl v5.40.0" "User Contributed Perl Documentation"
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.SH NAME
Pegex::Grammar \- Pegex Grammar Base Class
.SH SYNOPSIS
.IX Header "SYNOPSIS"
Define a Pegex grammar (for the Foo syntax):
.PP
.Vb 3
\&    package Pegex::Foo::Grammar;
\&    use base \*(AqPegex::Base\*(Aq;
\&    extends \*(AqPegex::Grammar\*(Aq;
\&
\&    has text => q{
\&    foo: bar baz
\&    ... rest of Foo grammar ...
\&    };
.Ve
.PP
then use it to parse some Foo:
.PP
.Vb 5
\&    use Pegex::Parser;
\&    my $parse_tree = Pegex::Parser\->new(
\&        grammar => \*(AqPegex::Foo::Grammar\*(Aq,
\&        receiver => \*(AqPegex::Tree\*(Aq,
\&    )\->parse(\*(Aqmy/file.foo\*(Aq);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Pegex::Grammar is a base class for defining your own Pegex grammar classes.
You just need to provide the grammar view the \f(CW\*(C`text\*(C'\fR or the \f(CW\*(C`file\*(C'\fR
attributes.
.PP
When Pegex::Parser uses your grammar, it will want it in the tree
(compiled) form, so Pegex::Grammar provides automatic compilation support.
.SH "PROPERTIES AND METHODS"
.IX Header "PROPERTIES AND METHODS"
.IP tree 4
.IX Item "tree"
This is the data structure containing the compiled grammar for your syntax. It
is usually produced by \f(CW\*(C`Pegex::Compiler\*(C'\fR. You can inline it in the \f(CW\*(C`tree\*(C'\fR
method, or else the \f(CW\*(C`make_tree\*(C'\fR method will be called to produce it.
.Sp
The \f(CW\*(C`make_tree\*(C'\fR method will call on Pegex::Compiler to compile the \f(CW\*(C`text\*(C'\fR
property by default. You can define your own \f(CW\*(C`make_tree\*(C'\fR method to do
override this behavior.
.Sp
Often times you will want to generate your own Pegex::Grammar subclasses in an
automated fashion. The Pegex and TestML modules do this to be performant. This
also allows you to keep your grammar text in a separate file, and often in a
separate repository, so it can be shared by multiple programming language's
module implementations.
.Sp
See
<https://github.com/ingydotnet/pegex\-pgx> and <https://github.com/ingydotnet/pegex\-pm/blob/master/lib/Pegex/Pegex/Grammar.pm>.
.IP text 4
.IX Item "text"
This is simply the text of your grammar, if you define this, you should
(probably) not define the \f(CW\*(C`tree\*(C'\fR property. This grammar text will be
automatically compiled when the \f(CW\*(C`tree\*(C'\fR is required.
.IP file 4
.IX Item "file"
This is the file where your Pegex grammar lives. It is usually used when you
are making a Pegex module. The path is relative to your top level module
directory.
.IP make_tree 4
.IX Item "make_tree"
This method is called when the grammar needs the compiled version.
.SH AUTHOR
.IX Header "AUTHOR"
Ingy döt Net <ingy@cpan.org>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2010\-2020. Ingy döt Net.
.PP
This program is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
.PP
See <http://www.perl.com/perl/misc/Artistic.html>