kw/parser-bundle

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Parser for context free grammars

dev-master 2013-11-26 14:15 UTC

Unknown License

• Kay Wienöbst

• parser
• parse
• parsing
• lr
• slr
• glr
• cfg
• context free grammar

README

This bundle provides a simple Lexer and a SLR Parser. Both classes can be accessed as a symfony service.

You must provide a context free grammar through configuration to make the tokenization and parsing work.

##Installation

1) download the composer package

$ php composer.phar require kw/parser-bundle:dev-master

2) Enable the Bundle

<?php
// app/AppKernel.php

public function registerBundles()
{
    $bundles = array(
        // ...
        new Kw\ParserBundle\KwParserBundle()	
    );
}

3) Configuration

####Lexer In order to use the Lexer, to tokenize a string into an array of tokens (which can then be parsed by the GLR Parser) you must provide a set of terminal symbols. Each terminal symbol consists of a name (in upper case letters) and a regular expression.

####Parser in order to make the parser do its work a specification of the context free grammar to parse is necessary. You need to specify the start production name and the production rules.

for the productions you must stick to the following conventions:

• all non terminal symbols must be written in lowercase
• all terminal symbols must be in upper case

Here is an example of a valid configuration for a simple CFG:

#app/config/config.yml
kw_parser:
    cfg:
        start: 'e'
        productions:
            e:
                - ['t']
                - ['e', 'T_PLUS', 't']
            t:
                - ['t', 'T_MULT', 'f']
                - ['f']
            f:
                - ['T_ID']
                - ['T_OPEN', 'e', 'T_CLOSE']
        terminals:
            T_PLUS: '\+'
            T_MULT: '\*'
            T_ID: 'id'
            T_OPEN: '\('
            T_CLOSE: '\)'