大学作业-词法分析器

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1、大学作业-词法分析器#include#includeusingnamespacestd;#defineMAX22charch='';stringkey[15]={"begin","end","if","then","else","while","write","read","do","call","const","char","until","procedure","repeat"};intIskey(stringc)//关键字判断{inti;for(i=0;i

2、return1;return0;}intIsLetter(charc)//判断是否为字母{if(((c<='z')&&(c>='a'))

3、

4、((c<='Z')&&(c>='A')))return1;elsereturn0;}intIsDigit(charc)//判断是否为数字{if(c>='0'&&c<='9')return1;elsereturn0;}voidanalyse(FILE*fpin){stringarr="";while((ch=fgetc(fpin))!=EOF){arr="";if(ch==''

5、

6、ch=='t'

7、

8、ch==''){}el

9、seif(IsLetter(ch)){while(IsLetter(ch)

10、

11、IsDigit(ch)){if((ch<='Z')&&(ch>='A'))ch=ch+32;arr=arr+ch;ch=fgetc(fpin);}fseek(fpin,-1L,SEEK_CUR);if(Iskey(arr)){cout<<"(关键字,"<

12、

13、ch=='.'&&IsDigit(fgetc(fpin

14、))){arr=arr+ch;ch=fgetc(fpin);}fseek(fpin,-1L,SEEK_CUR);cout<<"(常数,"<

15、"=="<<",EQ)"<':{ch=fgetc(fpin);if(ch=='=')cout<<"("<<">="<<",LB)"<"<<",-)"<

16、se{cout<<"("<<"<"<<",-)"<>in_fn;if((fpin=fopen(in_fn,"r"))!=NULL)break;elsecout<<"输入有误，请重新输入:";}cout<<"分析如下："<

17、out<>a;}