kw/parser-bundle

Parser for context free grammars

KwParserBundle

This bundle provides a simple Lexer and a SLR Parser. Both classes can be accessed as a symfony service., _(*1)

You must provide a context free grammar through configuration to make the tokenization and parsing work., _(*2)

Installation

1) download the composer package

``` bash $ php composer.phar require kw/parser-bundle:dev-master, <sub>(*3)</sub>

### 2) Enable the Bundle
``` php
<?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., <sub>(*4)</sub>

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., <sub>(*5)</sub>

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, <sub>(*6)</sub>

Here is an example of a valid configuration for a simple CFG:, <sub>(*7)</sub>

``` ymal, <sub>(*8)</sub>

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: '', <sub>(*9)</sub>

```, <sub>(*10)</sub>