1、 输入串应是词法分析的输出二元式序列，即某算术表达式“实验项目一”的输出结果。输出为输入串是否为该文法定义的算术表达式的判断结果。
2、 递归下降分析程序应能发现输入串出错。
3、 设计两个测试用例（尽可能完备，正确和出错），并给出测试结果
-1, input strings should be the output of lexical analysis of binary sequence, that is, the arithmetic expression of a
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SELECT `a`.`aid`,`a`.`title`,`a`.`create_time`,`m`.`username` FROM `jrk_downrecords` `a` INNER JOIN `jrk_member` `m` ON `a`.`uid`=`m`.`id` WHERE `a`.`status` = 1 GROUP BY `a`.`aid` ORDER BY `a`.`create_time` DESC LIMIT 10 [ RunTime:0.065547s ]
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SHOW FULL COLUMNS FROM `jrk_member` [ RunTime:0.000929s ]
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SHOW FULL COLUMNS FROM `jrk_searchrecords` [ RunTime:0.000815s ]
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SHOW FULL COLUMNS FROM `jrk_articles` [ RunTime:0.001179s ]
UPDATE `jrk_articles` SET `hits` = 2 WHERE `id` = 112357 [ RunTime:0.031987s ]
