NAME
Pegex::Grammar - Pegex Grammar Base Class
SYNOPSIS
Define a Pegex grammar (for the Foo syntax):
package Pegex::Grammar::Foo;
use base 'Pegex::Grammar';
use constant text => q{
foo: <bar> <baz>
... rest of Foo grammar ...
};
use constant receiver => 'Pegex::Receiver';
then use it to parse some Foo:
use Pegex::Grammar::Foo;
my $ast = Pegex::Grammar::Foo->parse('my/file.foo');
DESCRIPTION
Pegex::Grammar is a base class for defining your own Pegex grammar classes. It provides a single action method, `parse()`, that invokes a Pegex parser (usually Pegex::Parser) for you, and then returns the kind of result that you want it to. In other words, subclassing Pegex::Grammar is usually all you need to do to create a parser/compiler for your language/syntax.
Pegex::Grammar classes are very simple. You just need to define a text
property that returns your Pegex grammar string, or (if you don't want to incur the compilation of the grammar each time) a tree
property which returns a precompiled grammar.
You also need to define the receiver class or object that will produce a result from your parse. 'Pegex::Receiver' is the easiest choice, as long as you are satisfied which its results. Otherwise you can subclass it or define something different.
PROPERTIES
There are 2 properties of a Pegex::Grammar: tree
and text
.
- tree
-
This is the data structure containing the compiled grammar for your syntax. It is usually produced by
Pegex::Compiler
. You can inline it in thetree
method, or else themake_tree
method will be called to produce it.The
make_tree
method will call on Pegex::Compiler to compile thetext
property by default. You can define your ownmake_tree
method to do override this behavior.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. See the src/ subdirectory in http://github.com/ingydotnet/pegex-pm/.
- text
-
This is simply the text of your grammar, if you define this, you should (probably) not define the
tree
property. This grammar text will be automatically compiled when thetree
is required.
AUTHOR
Ingy döt Net <ingy@cpan.org>
COPYRIGHT AND LICENSE
Copyright (c) 2010, 2011, 2012. Ingy döt Net.
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
See http://www.perl.com/perl/misc/Artistic.html