christophercastro / slr-phparser
A very simple LR(1) parser generator written in PHP.
dev-master
2015-05-11 11:16 UTC
Requires
- php: >=5.3
This package is not auto-updated.
Last update: 2024-05-21 14:35:15 UTC
README
A very simple LR(0) and LR(1) parser generator written in PHP.
Example
Simple calculator with operator precedence:
use Phparser\Grammar\Grammar; use Phparser\Lexer\Lexer; use Phparser\Parser\Parser; use Phparser\Rule\LR1\RulesCollection; /** * This will be used to hold the result of the calculator. */ $RESULT = 0; /** * Calculator's language definition. */ $productions = new RulesCollection([ 'S -> exp_a' => function ($info) { global $RESULT; $info = $info[0]; $RESULT = $info; }, 'exp_a -> exp_a T_PLS exp_a ' => function (&$info) { $info = $info[0] + $info[2]; }, 'exp_a -> exp_a T_SUB exp_a' => function (&$info) { $info = $info[0] - $info[2]; }, 'exp_a -> exp_a T_MUL exp_a' => function (&$info) { $info = $info[0] * $info[2]; }, 'exp_a -> exp_a T_DIV exp_a' => function (&$info) { $info = $info[0] / $info[2]; }, 'exp_a -> T_LP exp_a T_RP' => function (&$info) { $info = $info[1]; }, 'exp_a -> T_SQRT T_LP exp_a T_RP' => function (&$info) { $info = sqrt($info[2]); }, 'exp_a -> T_NUM' => function (&$info) { $info = intval($info[0]->value()); }, ]); /** * Tokens definition. */ $tokens = [ '\*' => 'T_MUL', '\/' => 'T_DIV', '\+' => 'T_PLS', '\-' => 'T_SUB', 'sqrt' => 'T_SQRT', '[0-9]+' => 'T_NUM', '\(' => 'T_LP', '\)' => 'T_RP', '\s+|\n+|\t+' => '', ]; /** * Startup the parser. */ $lexer = new Lexer($tokens); $grammar = new Grammar($productions); $parser = new Parser($lexer, $grammar); /** * Configure tokens precedence. */ $grammar->prec('T_MUL', 4); $grammar->prec('T_DIV', 3); $grammar->prec('T_SUB', 2); $grammar->prec('T_PLS', 1); /** * The expression to parse. */ $exp = '50 + 20 * 3 / 2 - 1'; /** * Run the parser. */ $parser->run($exp); /** * Draw parsing table. */ require 'tests/config/drawer.php'; echo "<h2>Parsing table:</h2>"; echo draw_table($grammar->transitionTable()->toArray());