词法分析器!内有文档!本程序识别的关键字为int real if then else while，仅当单独出现以上标识符时识别为关键字，对于inta,ifb等识别为标识符。 操作符分隔符! -lexical analyzer! Have documentation! The procedures for the identification of the keyword int el real if then se while, and only if there alone at the