104 lines
2.6 KiB
ReStructuredText
104 lines
2.6 KiB
ReStructuredText
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Simple Parser Example
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=====================
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Extend the ``Doctrine\Common\Lexer\AbstractLexer`` class and implement
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the ``getCatchablePatterns``, ``getNonCatchablePatterns``, and ``getType``
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methods. Here is a very simple example lexer implementation named ``CharacterTypeLexer``.
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It tokenizes a string to ``T_UPPER``, ``T_LOWER`` and``T_NUMBER`` tokens:
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.. code-block:: php
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<?php
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use Doctrine\Common\Lexer\AbstractLexer;
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/**
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* @extends AbstractLexer<CharacterTypeLexer::T_*, string>
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*/
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class CharacterTypeLexer extends AbstractLexer
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{
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const T_UPPER = 1;
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const T_LOWER = 2;
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const T_NUMBER = 3;
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protected function getCatchablePatterns(): array
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{
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return [
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'[a-bA-Z0-9]',
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];
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}
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protected function getNonCatchablePatterns(): array
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{
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return [];
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}
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protected function getType(&$value): int
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{
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if (is_numeric($value)) {
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return self::T_NUMBER;
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}
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if (strtoupper($value) === $value) {
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return self::T_UPPER;
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}
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if (strtolower($value) === $value) {
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return self::T_LOWER;
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}
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}
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}
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Use ``CharacterTypeLexer`` to extract an array of upper case characters:
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.. code-block:: php
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<?php
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class UpperCaseCharacterExtracter
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{
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public function __construct(private CharacterTypeLexer $lexer)
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{
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}
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/** @return list<string> */
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public function getUpperCaseCharacters(string $string): array
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{
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$this->lexer->setInput($string);
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$this->lexer->moveNext();
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$upperCaseChars = [];
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while (true) {
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if (!$this->lexer->lookahead) {
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break;
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}
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$this->lexer->moveNext();
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if ($this->lexer->token->isA(CharacterTypeLexer::T_UPPER)) {
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$upperCaseChars[] = $this->lexer->token->value;
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}
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}
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return $upperCaseChars;
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}
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}
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$upperCaseCharacterExtractor = new UpperCaseCharacterExtracter(new CharacterTypeLexer());
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$upperCaseCharacters = $upperCaseCharacterExtractor->getUpperCaseCharacters('1aBcdEfgHiJ12');
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print_r($upperCaseCharacters);
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The variable ``$upperCaseCharacters`` contains all of the upper case
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characters:
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.. code-block:: php
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Array
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(
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[0] => B
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[1] => E
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[2] => H
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[3] => J
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)
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This is a simple example but it should demonstrate the low level API
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that can be used to build more complex parsers.
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