scriptbox

DslExpression.class.php (6055B)

---

 <?php
 
 namespace dsl\ast;
 
 define('LEFT', 0);
 define('RIGHT', 1);
 
 use dsl\DslParserException;
 use dsl\DslToken;
 
 class DslExpression extends DslElement implements DslStatement
 {
 	private $value;
 
 	public function __construct( $valueTokens )
 	{
 		$this->parse( $valueTokens );
 	}
 
 	public function execute( & $context ) {
 
 		if   ( is_array( $this->value ) )
 			foreach( $this->value as $v)
 				$v->execute( $context );
 		else
 			return $this->value->execute( $context );
 	}
 
 	/**
 	 * @param DslToken[] $tokens
 	 * @throws DslParserException
 	 */
 	public function parse($tokens)
 	{
 		//echo "<h5>Expression:</h5><pre>"; var_export( $tokens ); echo "</pre>";
 		if   ( ! $tokens ) {
 			$this->value = new DslNull();
 			return;
 		}
 
 		$this->parseExpression( $tokens );
 		// Groups
 	}
 
 
 	/**
 	 * Parsing an expression using the shunting yard algorithm.
 	 *
 	 *  Precedences see https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Operators/Operator_Precedence#assoziativit%C3%A4t
 	 * @param DslToken[] $tokens
 	 * @throws DslParserException
 	 */
 	private function parseExpression( $tokens )
 	{
 		$precedence = [
 			','  =>  2,
 			'='  =>  3,
 			'+=' =>  3,
 			'-=' =>  3,
 			'||' =>  5,
 			'&&' =>  6,
 			'==' => 10,
 			'!=' => 10,
 			'<'  => 11,
 			'<=' => 11,
 			'>'  => 11,
 			'>=' => 11,
 			'+'  => 13,
 			'-'  => 13,
 			'/'  => 14,
 			'*'  => 14,
 			'%'  => 14,
 			'**' => 15,
 			'!'  => 16,
 			'$'  => 19, // function call, provided by the lexer
 			'.'  => 19,
 		];
 
 		$assoc = [
 			','   => LEFT,
 			'='   => RIGHT,
 			'-='  => RIGHT,
 			'+='  => RIGHT,
 			'||'  => LEFT,
 			'&&'  => LEFT,
 			'=='  => LEFT,
 			'!='  => LEFT,
 			'<'   => LEFT,
 			'<='  => LEFT,
 			'> '  => LEFT,
 			'>='  => LEFT,
 			'+'   => LEFT,
 			'-'   => LEFT,
 			'/'   => LEFT,
 			'*'   => LEFT,
 			'%'   => LEFT,
 			'^'   => RIGHT,
 			'!'   => RIGHT,
 			'**'  => RIGHT,
 			'.'   => RIGHT,
 			'$'   => LEFT,
 		];
 
 
 		// for the purpose of comparing only; it's forced to top priority explicitly
 		$precedence['('] = 0;
 		$precedence[')'] = 0;
 
 		$output_queue   = [];
 		$operator_stack = [];
 
 		if   ( $tokens instanceof DslStatement ) {
 
 			$this->value = $tokens;
 			return;
 		}
 
 		if   ( $tokens instanceof DslToken )
 			$tokens = [$tokens];
 
 		if   ( ! is_array($tokens))
 			throw new DslParserException("tokens must be an array, but it is ".get_class($tokens));
 
 		// while there are tokens to be read:
 		while ( $tokens ) {
 			// read a token.
 			$token = array_shift($tokens);
 
 			if ($token->isOperator() ) {
 
 				// while there is an operator at the top of the operator stack with
 				// greater than or equal to precedence:
 				while ($operator_stack &&
 					$precedence[end($operator_stack)->value] >= $precedence[$token->value] + $assoc[$token->value]) {
 					// pop operators from the operator stack, onto the output queue.
 
 					$left  = array_pop( $output_queue );
 					$right = array_pop( $output_queue );
 					$output_queue[] = $this->createNode( array_pop($operator_stack),$left,$right );
 				}
 				// push the read operator onto the operator stack.
 				$operator_stack[] = $token;
 
 				// if the token is a left bracket (i.e. "("), then:
 			} elseif ($token->value === '(') {
 				// push it onto the operator stack.
 				$operator_stack[] = $token;
 
 				// if the token is a right bracket (i.e. ")"), then:
 			} elseif ($token->value === ')') {
 				// while the operator at the top of the operator stack is not a left bracket:
 				while (end($operator_stack)->value !== '(') {
 					// pop operators from the operator stack onto the output queue.
 					$left  = array_pop( $output_queue );
 					$right = array_pop( $output_queue );
 					$output_queue[] = $this->createNode( array_pop($operator_stack),$left,$right );
 
 					// /* if the stack runs out without finding a left bracket, then there are
 					// mismatched parentheses. */
 					if (!$operator_stack) {
 						throw new DslParserException("Mismatched ')' parentheses");
 					}
 				}
 
 				// pop the left bracket from the stack.
 				array_pop($operator_stack);
 
 			}
 			elseif		// if the token is a number, then push it to the output queue.
 				    (true) {
 					$output_queue[] = $this->tokenToStatement( $token );
 
 					// if the token is an operator, then:
 			} else {
 				throw new DslParserException( 'Unexpected token '.$token->value, $token->lineNumber);
 			}
 		} // if there are no more tokens to read:
 
 		// while there are still operator tokens on the stack:
 		while ($operator_stack) {
 			$token = array_pop($operator_stack);
 
 			// if the operator token on the top of the stack is a bracket, then
 			// there are mismatched parentheses.
 			if ($token->type == DslToken::T_OPERATOR && $token->value == '(') {
 				throw new DslParserException( "Mismatched '(' parentheses");
 			}
 			// pop the operator onto the output queue.
 			$left  = array_pop( $output_queue );
 			$right = array_pop( $output_queue );
 			$output_queue[] = $this->createNode( $token,$left,$right );
 		}
 
 		$this->value = $output_queue[0];
 	}
 
 	/**
 	 * @param $op DslToken
 	 * @param $left
 	 * @param $right
 	 * @throws DslParserException
 	 */
 	private function createNode($op, $left, $right)
 	{
 		if   ( $op->value == '=' )
 			return new DslAssignment( $right,$left );
 		if   ( $op->value == ',' )
 			return new DslSequence( $right,$left );
 		if   ( $op->value == '.' )
 			return new DslProperty( $right, $left );
 		if   ( $op->value == '$' )
 			return new DslFunctionCall( $right, $left );
 		else
 			return new DslOperation( $op->value,$right,$left );
 	}
 
 	/**
 	 * @param $token DslToken
 	 */
 	private function tokenToStatement($token)
 	{
 		switch( $token->type ) {
 			case DslToken::T_NONE:
 				return new DslInteger( 0 );
 			case DslToken::T_NUMBER:
 				return new DslInteger( $token->value );
 			case DslToken::T_TEXT:
 				return new DslString( $token->value );
 			case DslToken::T_STRING:
 				return new DslVariable( $token->value );
 			case DslToken::T_DOT:
 				return new DslProperty( $token->value );
 			default:
 				throw new DslParserException('Unknown token '.$token->value,$token->lineNumber);
 		}
 	}
 }