C++实现词法分析.doc

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1、#include#include#include#include#defineRWD8#defineOPEAR11#defineSEPAR6usingnamespacestd;//构建符号表stringRword[RWD]={"if","int","for","while","do","return","break","continue"};stringOpear[OPEAR]={"+","-","*","/","=",">","<",">=","<=","!=","

2、=="};stringSepar[SEPAR]={",",";","{","}","(",")"};voidmain(){vectorinput;vector::iteratoriter;/*将源代码中的单词从文件中读出按成分存放在input中*/ifstreammyf;stringstr="";myf.open("1.txt");if(myf.fail()){cout<<"error!"<

3、SEPAR;i++)//判断是否为分隔符{stringtemp="";temp+=ch;if(temp==Separ[i]){if(str!=""){input.push_back(str);str="";}str=ch;input.push_back(str);str="";ch=myf.get();break;}}if(ch=='t'

4、

5、ch==''

6、

7、ch=='')//判断是否为空格，回车{if(str!=""){input.push_back(str);str="";}ch=myf.get();}elseif(ch=='!

8、'

9、

10、ch=='>'

11、

12、ch=='<'

13、

14、ch=='=')//判断是否为运算符{if(str!=""){input.push_back(str);str="";}str=ch;ch=myf.get();if(ch=='='){str+=ch;input.push_back(str);ch=myf.get();str="";}else{input.push_back(str);}}elseif(ch=='+'

15、

16、ch=='-'

17、

18、ch=='*'

19、

20、ch=='/'){if(str!=""){input.push_back(str);str=

21、"";}str+=ch;input.push_back(str);ch=myf.get();str="";}else{str+=ch;ch=myf.get();}}myf.close();/*读文件结束*//*进行词法分析，并输出*/for(iter=input.begin();iter!=input.end();iter++){intsign=0;for(inti=0;i

22、eak;}}if(sign==0)//判断是否为运算符{for(inti=0;i

23、((*iter)[0]>'0'&&(*iter)[0]<='9')cout<<"(3,""<<*iter<<"")"<