vendor/twig/twig/lib/Twig/ExpressionParser.php

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<?php

/*
 * This file is part of Twig.
 *
 * (c) Fabien Potencier
 * (c) Armin Ronacher
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

/**
 * Parses expressions.
 *
 * This parser implements a "Precedence climbing" algorithm.
 *
 * @see http://www.engr.mun.ca/~theo/Misc/exp_parsing.htm
 * @see http://en.wikipedia.org/wiki/Operator-precedence_parser
 *
 * @author Fabien Potencier <fabien@symfony.com>
 *
 * @internal
 */
class Twig_ExpressionParser
{
    const OPERATOR_LEFT = 1;
    const OPERATOR_RIGHT = 2;

    protected $parser;
    protected $unaryOperators;
    protected $binaryOperators;

    private $env;

    public function __construct(Twig_Parser $parser, $env = null)
    {
        $this->parser = $parser;

        if ($env instanceof Twig_Environment) {
            $this->env = $env;
            $this->unaryOperators = $env->getUnaryOperators();
            $this->binaryOperators = $env->getBinaryOperators();
        } else {
            @trigger_error('Passing the operators as constructor arguments to '.__METHOD__.' is deprecated since version 1.27. Pass the environment instead.', E_USER_DEPRECATED);

            $this->env = $parser->getEnvironment();
            $this->unaryOperators = func_get_arg(1);
            $this->binaryOperators = func_get_arg(2);
        }
    }

    public function parseExpression($precedence = 0)
    {
        $expr = $this->getPrimary();
        $token = $this->parser->getCurrentToken();
        while ($this->isBinary($token) && $this->binaryOperators[$token->getValue()]['precedence'] >= $precedence) {
            $op = $this->binaryOperators[$token->getValue()];
            $this->parser->getStream()->next();