Tiny语言的词法分析器-C+版-课程设计报告

1、实 验 报 告 学号： 姓名： 专业：计算机科学与技术 班级：2班 第9周 课程名称 编译原理课程设计 实验课时8实验项目手工构造Tiny语言的词法分析器实验时间7-10周实验目的 熟悉Tiny语言词法；构造DFA；设计数据类型、数据结构；用C+实现Tiny语言的词法分析器实验环境 Windows 10 专业版 Microsoft Visual Studio 2013实验内容（算法、程序、步骤和方法） 一、Tiny语言记号Reserved wordsSpecial SymbolsOtherif+number(1 or more digits)then-else*endrepeat=until/

2、identifier(1 or more letters)read(write);:=二、构造Tiny语言DFAID：letter(letter)*Number: digit(digit)*三、根据DFA编写词法分析器#include#include#includeusing namespace std;static int rowCounter = 1;/静态变量，用于存储行数static bool bracketExist = false;/判断注释存在与否，false为不存在class Lexpublic:ofstream output;string line = ;Lex(string

3、 inputLine)line = inputLine;scan(Trim(line);rowCounter+;string Trim(string &str)/函数用于去除每行前后空格int s = str.find_first_not_of( t);int e = str.find_last_not_of( t);str = str.substr(s, e - s + 1);str += 0;return str;void scan(string inputLine)ofstream output;output.open(SampleOutput.txt, ios:app);string

4、line = inputLine;int i = 0;string str = ;int temp;string token = ;output rowCounter : line endl;/输出每行while (linei != 0)/根据DFA扫描并判断if (linei = )/注释bracketExist = true;if (bracketExist = true)output t rowCounter : ;while (linei != )output linei;/不处理，直接输出if (linei + 1 != NULL)i+;elsebreak;if (linei = )

5、/注释结束output lineiendl;bracketExist = false;if (bracketExist = false)/数字while (isdigit(linei)temp = temp * 10 + linei;if (!isdigit(linei + 1)output t rowCounter : NUM, val= temp - 0 = a&linei = A&linei = a&linei + 1 = A&linei + 1 = Z) | linei + 1 = | linei + 1 = | linei + 1 = | linei + 1 = NULL)if (i

6、sToken(token)output t rowCounter : token endl;elseint j = 0;while (tokenj != 0)output t rowCounter : tokenj = a&linei = A&linei = a&linei + 1 = A&linei + 1 = Z)if (isResearvedWord(str) /判断是否是保留字output t rowCounter : Reversed Word: str endl;break;elseoutput t rowCounter : ID, name= str endl;break;if

7、(linei + 1 != NULL)i+;str = ;if (linei + 1 != NULL)i+;elsebreak;if (linei + 1 = NULL)if (linei = ;)output t rowCounter : linei;break;/清空，以备下一行读取line = ;str = ;temp = 0;token = ;output endl;output.close();bool isResearvedWord(string s)/存储保留字，并判断string reservedWord8 = if, then, else, end, repeat, unti

8、l, read, write ;bool judge = false;for (int i = 0; i 8; i+)if (s = reservedWordi)judge = true;break;return judge;bool isToken(string s)/存储符号，并判断string token10 = +, -, *, /, =, , (, ), ;, := ;bool judge = false;for (int i = 0; i 10; i+)if (s = tokeni)judge = true;break;return judge;int main()ifstream

9、 input;input.open(SampleInput.tny);string line50;int i = 0;while (getline(input, linei)/cout linei endl;i+;input.close();cout endl endl Reading source file completed! endl;int j = 0;remove(SampleOutput.txt);for (j = 0; j i; j+)Lex lex(linej);cout endl endl Writing file completed! endl endl endl;retu

10、rn 0;四、重要数据结构string line:用于存储每一行的字符，并逐个读取分析。string token:用于存储TINY语言的符号，并调用遍历进行判断。string reservedWord:用于存储TINY语言的保留字，遍历进行判断，若为真，则输出Reserved word。static int rowCounter:静态变量，存储行号，每创建一个类的实例便加一。int temp:用于存储数字，并输出。static int bracketExist:静态变量，标记注释是否存在。string token, str分别用于临时存储读取的符号的字母串。五、算法总结 建立Lex class

11、，并读取每一行，创建Lex的实例，在Lex中处理。先判断是否在注释范围内，若是，则输出注释内容，直至产生“”字符。若不在注释区内，则读取单个字符，根据DFA进行判断。若为符号，则当下一个字符不是符号时输出；若为数字，则继续往下读，直至下一个字符不是数字为止，输出。若为字母，继续读取，直至下一个字符不是字母，把这一串字母和预先定义的保留字比对，若是，则输出“Reserved word”，若不是，则输出“ID，name=”字样。一行处理完毕，便开始创建下一行实例，直至文件尾。数据记录和计算 Tiny测试程序结 论（结 果） 1: Sample program1: Sample program2:

12、in TINY language -2: in TINY language -3: computes factorial3: computes factorial4: 4: 5: read x; input an integer 5: Reversed Word: read5: ID, name= x5: ;5: input an integer 6: if 0 x then dont compute if x = 0 6: Reversed Word: if6: NUM, val= 06: 6: ID, name= x6: Reversed Word: then6: dont compute

13、 if x = 0 7: fact := 1;7: ID, name= fact7: :=7: NUM, val= 17: ;8: repeat8: Reversed Word: repeat9: fact := fact * x;9: ID, name= fact9: :=9: ID, name= fact9: *9: ID, name= x9: ;10: x := x - 1;10: ID, name= x10: :=10: ID, name= x10: -10: NUM, val= 110: ;11: until x = 0;11: Reversed Word: until11: ID, name= x11: =11: NUM, val= 011: ;12: write fact output factorial of x 12: Reversed Word: w