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<?php |
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/** |
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* This file is part of PHP-Yacc package. |
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* |
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* For the full copyright and license information, please view the LICENSE |
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* file that was distributed with this source code. |
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*/ |
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declare(strict_types=1); |
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namespace PhpYacc\Lalr; |
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use PhpYacc\Exception\LogicException; |
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use PhpYacc\Yacc\Production; |
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class Item implements \ArrayAccess, \IteratorAggregate |
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{ |
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/** |
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* @var Production |
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*/ |
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protected $production; |
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/** |
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* @var int |
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*/ |
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protected $pos = 0; |
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/** |
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* Item constructor. |
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* |
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* @param Production $production |
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* @param int $offset |
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*/ |
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public function __construct(Production $production, int $offset) |
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{ |
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\assert($offset >= 1); |
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\assert($offset <= \count($production->body)); |
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$this->production = $production; |
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$this->pos = $offset; |
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} |
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/** |
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* @return \Generator |
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*/ |
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public function getIterator(): \Generator |
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{ |
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for ($i = $this->pos, $l = \count($this->production->body); $i < $l; $i++) { |
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yield $this->production->body[$i]; |
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} |
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} |
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/** |
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* @param int $n |
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* |
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* @return Item |
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*/ |
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public function slice(int $n): self |
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{ |
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return new self($this->production, $this->pos + $n); |
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} |
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/** |
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* @param mixed $index |
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* |
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* @return bool |
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*/ |
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public function offsetExists($index) |
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{ |
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return isset($this->production->body[$index + $this->pos]); |
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} |
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/** |
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* @param mixed $index |
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* |
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* @throws LogicException |
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* |
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* @return \PhpYacc\Grammar\Symbol |
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*/ |
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public function offsetGet($index) |
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{ |
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if (!$this->offsetExists($index)) { |
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throw new LogicException("Offset $index does not exist"); |
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} |
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return $this->production->body[$index + $this->pos]; |
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} |
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/** |
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* @param mixed $index |
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* @param mixed $value |
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* |
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* @throws LogicException |
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*/ |
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public function offsetSet($index, $value) |
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{ |
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throw new LogicException('Not supported'); |
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} |
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/** |
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* @param mixed $index |
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* |
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* @throws LogicException |
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* |
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* @return void |
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*/ |
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public function offsetUnset($index) |
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{ |
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throw new LogicException('Not supported'); |
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} |
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/** |
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* @return bool |
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*/ |
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public function isHeadItem(): bool |
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{ |
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return $this->pos === 1; |
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} |
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/** |
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* @return bool |
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*/ |
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public function isTailItem(): bool |
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{ |
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return $this->pos === \count($this->production->body); |
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} |
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/** |
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* @return Production |
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*/ |
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public function getProduction(): Production |
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{ |
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return $this->production; |
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} |
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/** |
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* @return int |
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*/ |
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public function getPos(): int |
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{ |
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return $this->pos; |
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} |
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/** |
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* @return string |
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*/ |
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public function __toString() |
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{ |
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$result = '('.$this->production->num.')'; |
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for ($i = 0, $l = \count($this->production->body); $i < $l; $i++) { |
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if ($i === 1) { |
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$result .= ' :'; |
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} |
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if ($i === $this->pos) { |
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$result .= ' .'; |
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} |
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$result .= ' '.$this->production->body[$i]->name; |
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} |
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if ($i === 1) { |
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$result .= ' :'; |
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} |
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if ($i === $this->pos) { |
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$result .= ' .'; |
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} |
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return $result; |
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} |
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} |
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stenin-nikita /
PHP-Yacc
