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<?php |
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/****************************************************************************** |
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* An implementation of dicto (scg.unibe.ch/dicto) in and for PHP. |
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* |
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* Copyright (c) 2016 Richard Klees <[email protected]> |
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* |
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* This software is licensed under The MIT License. You should have received |
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* a copy of the license along with the code. |
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*/ |
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namespace Lechimp\Dicto\Definition; |
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/** |
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* Baseclass for Parsers. |
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*/ |
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abstract class Parser { |
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/** |
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* @var SymbolTable |
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*/ |
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private $symbol_table; |
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/** |
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* @var Tokenizer|null |
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*/ |
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protected $tokenizer = null; |
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/** |
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* @var array|null (Symbol, array $matches) |
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*/ |
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protected $token = null; |
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public function __construct() { |
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$this->symbol_table = $this->create_symbol_table(); |
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$this->add_symbols_to($this->symbol_table); |
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} |
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/** |
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* Parse the string according to this parser. |
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* |
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* @return mixed |
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*/ |
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public function parse($source) { |
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try { |
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$this->tokenizer = $this->create_tokenizer($source); |
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$this->token = $this->tokenizer->current(); |
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return $this->root(); |
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} |
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finally { |
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$this->tokenizer = null; |
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$this->token = null; |
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} |
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} |
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/** |
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* The root for the parse tree. |
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* |
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* @return mixed |
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*/ |
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abstract protected function root(); |
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// Factory Methods |
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/** |
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* Build the Tokenizer. |
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* |
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* @return Tokenizer |
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*/ |
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public function create_tokenizer($source) { |
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assert('is_string($source)'); |
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return new Tokenizer($this->symbol_table, $source); |
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} |
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/** |
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* Build the SymbolTable |
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* |
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* @return SymbolTable |
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*/ |
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37 |
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protected function create_symbol_table() { |
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return new SymbolTable(); |
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} |
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/** |
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* @param SymbolTable |
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* @return null |
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*/ |
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abstract protected function add_symbols_to(SymbolTable $table); |
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// Helpers for defining the grammar. |
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// Helpers for actual parsing. |
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/** |
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* Set the current token to the next token from the tokenizer. |
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* |
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* @return null |
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*/ |
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protected function fetch_next_token() { |
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assert('is_array($this->token)'); |
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assert('$this->tokenizer !== null'); |
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$this->tokenizer->next(); |
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$this->token = $this->tokenizer->current(); |
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} |
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/** |
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* Get the current symbol. |
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* |
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* @return Symbol |
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*/ |
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protected function current_symbol() { |
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return $this->token[0]; |
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} |
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/** |
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* Get the current match. |
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* |
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* @return string[] |
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*/ |
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protected function current_match() { |
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return $this->token[1]; |
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} |
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/** |
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* Advance the tokenizer to the next token if current token |
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* was matched by the given regexp. |
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* |
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* @param string $regexp |
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* @return null |
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*/ |
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protected function advance($regexp) { |
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assert('is_string($regexp)'); |
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assert('is_array($this->token)'); |
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assert('$this->tokenizer !== null'); |
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if (!$this->is_current_token_matched_by($regexp)) { |
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throw new ParserException("Syntax Error: Expected '$regexp'"); |
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} |
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$this->tokenizer->next(); |
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$this->token = $this->tokenizer->current(); |
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} |
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/** |
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* Advance the tokenizer to the next token if current token |
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* was matched by the given operator. |
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* |
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* @param string $op |
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* @return null |
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*/ |
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protected function advance_operator($op) { |
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$this->advance($this->symbol_table->operator_regexp($op)); |
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} |
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/** |
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* Is the end of the file reached? |
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* |
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* @return bool |
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*/ |
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public function is_end_of_file_reached() { |
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return $this->is_current_token_matched_by(""); |
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} |
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/** |
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* Check if the current token was matched by the given regexp. |
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* |
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* @param string $regexp |
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* @return bool |
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*/ |
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protected function is_current_token_matched_by($regexp) { |
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assert('is_string($regexp)'); |
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return $this->token[0]->regexp() == $regexp; |
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} |
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/** |
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* Check if the current token is the given operator. |
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* |
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* @param string $operator |
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* @return bool |
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*/ |
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protected function is_current_token_operator($operator) { |
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return $this->is_current_token_matched_by |
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($this->symbol_table->operator_regexp($operator)); |
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} |
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} |
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lechimp-p /
dicto.php
