一、实验目的

实现一个递归下降语法分析程序，识别用户输入的算术表达式。

二、实验主要内容

1、文法如下：

E® TE`　　

E’® +TE’|-TE’|e

　　T® FT`

　　T’® *FT’|/FT’|e

　　F® (E)|i

2、求取各非终结符的First及Follow集合

3、编程实现下降递归分析法，识别从键盘输入的关于整数或浮点数的算术表达式（在此，上述文法中的i代表整数或浮点数）

4、对于语法错误，要指出错误具体信息。

5、运行实例如下：

-First, the purpose of the experiment to achieve a recursive descent parser to identify the user input an arithmetic expression. Second, the main contents of the experiment, the following grammar: ETE `E' +TE ' '　|-TE ' | e TFT` T' * FT ' |/FT'　| e F (E) | i to strike each nonterminal First and Follow collections of 3 programming fall recursive analysis, identification entered from the keyboard on integer or floating-point arithmetic expression (in this case, the grammar i represents an integer or floating point) for syntax errors, to point out that the error specific information. 5, the running instance as follows: