documentBison Parser

Bison Parser

License: MIT Docs PHP Version Ask DeepWiki

Bison Parser reads GNU Bison grammar files (.y, .yy) into a syntax tree that keeps everything the file says, with the position of each part. It reads the language the GNU Bison manual defines, so a file Bison accepts is read as Bison reads it and a file Bison rejects raises an error at the same place. The manual is the specification, and spec/features states it clause by clause as scenarios that run the parser.

It reads grammars; it does not generate parsers. The tree is for tools that analyse, transform, document or generate from Bison grammars.

Requirements

• PHP 8.1+

Installation

composer require k-kinzal/bison-parser

Usage

use BisonParser\Parser;

$file = (new Parser())->parse(file_get_contents('grammar.y'));

foreach ($file->declarations as $declaration) {
    echo $declaration::class, ' at ', $declaration->location(), "\n";
}
foreach ($file->rules() as $rule) {
    echo $rule->name->value, ': ', count($rule->alternatives), " alternatives\n";
    foreach ($rule->alternatives as $alternative) {
        foreach ($alternative->symbols() as $symbol) {
            echo '  ', $symbol->kind->value, ' ', $symbol->value, "\n";
        }
    }
}

A tree prints back as a grammar file, and printing is stable, which is how a tree can be checked:

use BisonParser\Printer\Printer;

$text = (new Printer())->print($file);

Every node of the tree is described in the API documentation.

License

MIT License. See LICENSE for details.