解释器模式的一个简单示例

来源：互联网发布：战地2网络对战平台编辑：程序博客网时间：2024/05/01 10:39
<?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, $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) );
0 0