PHP解释器模式的一个简单示例分享

PHP解释器模式的一个简单示例分享

<?php// 解释器模式abstract class Expression{	private static $keyCount = 0;	private $key = NULL;	abstract function interpret(InterpreterContext $ctx);	/**	 * as array key	 * @return auto increment value	 */	public function getKey()	{		if(!isset($this->key)) {			self::$keyCount++;			$this->key = self::$keyCount;		}		return $this->key;	}}/** * context */class InterpreterContext{	private $expressionstore = array();	/**	 * store value	 */	public function replace(Expression $exp, $value)	{		$this->expressionstore[$exp->getKey()] = $value;	}	/**	 * find value	 */	public function lookup(Expression $exp)	{		return $this->expressionstore[$exp->getKey()];	}}/** * literal expression */class LiteralExpression extends Expression{	private $value;	public function construct($value)	{		$this->value = $value;	}	public function interpret(InterpreterContext $ctx)	{		$ctx->replace($this, $this->value);	}}/** * var=value expression */class VariableExpression extends Expression{	private $name;	private $val;	public function construct($name, $val=null)	{		$this->name = $name;		$this->val = $val;	}	public function interpret(InterpreterContext $ctx)	{		if(!is_null($this->val)) {			$ctx->replace($this, $this->val);			$this->val = null;		}	}	public function setValue($value)	{		$this->val = $value;	}	/**	 * @override	 */	public function getKey()	{		return $this->name;	}}abstract class OperatorExpression extends Expression{	protected $l_op;	protected $r_op;	public function construct(Expression $l, Expression $r)	{		$this->l_op = $l;		$this->r_op = $r;	}	/**	 * @param $ctx 		 InterpreterContext	 * @param $result_l  Expression $l's result	 * @param $result_r  Expression $r's result	 */	protected abstract function doInterpret(InterpreterContext $ctx, 		$result_l, $result_r);	public function interpret(InterpreterContext $ctx)	{		$this->l_op->interpret($ctx);		$this->r_op->interpret($ctx);		$result_l = $ctx->lookup($this->l_op);		$result_r = $ctx->lookup($this->r_op);		$this->doInterpret($ctx, $result_l, $result_r);	}}/** * equals */class EqualsExpression extends OperatorExpression{	protected function doInterpret(InterpreterContext $ctx, $result_l, $result_r)	{		$ctx->replace($this, $result_l == $result_r);	}}/** * or */class BooleanOrExpression extends OperatorExpression{	protected function doInterpret(InterpreterContext $ctx,<i>·本2文来源gaodai$ma#com搞$代*码网2</i><strong>搞gaodaima代码</strong> $result_l, $result_r)	{		$ctx->replace($this, $result_l || $result_r);	}}/** * and */class BooleanAndExpression extends OperatorExpression{	protected function doInterpret(InterpreterContext $ctx, $result_l, $result_r)	{		$ctx->replace($this, $result_l && $result_r);	}}/** * not */class BooleanNotExpression extends Expression{	private $expr;		public function construct(Expression $e) {		$this->expr = $e;	}		public function interpret(InterpreterContext $ctx) {		$this->expr->interpret($ctx);		$ctx->replace($this, !$ctx->lookup($this->expr));	}}// test code/*$ctx = new InterpreterContext();$literarl = new LiteralExpression('four');$literarl->interpret($ctx);// echo $ctx->lookup($literarl);$variable = new VariableExpression('input', '444');$variable->interpret($ctx);// echo $ctx->lookup($variable);$answer = new VariableExpression('input');$answer->interpret($ctx);echo $ctx->lookup($answer);*/// $input equas four or $input equals 4$ctx = new InterpreterContext();$input = new VariableExpression('input');$statement = new BooleanOrExpression(	new EqualsExpression($input, new LiteralExpression('four')),	new EqualsExpression($input, new LiteralExpression(4)));$input->setValue('four');$statement->interpret($ctx);var_dump($ctx->lookup($statement)); // true$input->setValue(4);$statement->interpret($ctx);var_dump($ctx->lookup($statement)); // true$input->setValue(42);$statement->interpret($ctx);var_dump($ctx->lookup($statement)); // false$not = new BooleanNotExpression($statement); // true$not->interpret($ctx);var_dump( $ctx->lookup($not) );

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