需要实现的词法分析程序的功能是，接受一个表达式，输出该表达式中的各类单词符号。测试词法分析程序时，可以按照一定格式输出各类单词符号。-Need to implement the functions of lexical analysis procedure is to accept an expression, the output of the expression of various types of word symbols. When testing lexical analysis