PL/0 词法分析器

PL/0 词法分析器

 #include<stdio.h>
 #include <ctype.h>
 #include <stdlib.h>
 #include <string.h>

 typedef enum SymEnum
 {
     Identifier=, //标识符
     Const=,  //常数
     Key=,    //关键字
     Operator=,   //运算符
     Delimiter=   //界符
 } SymEnum;

 char KeyWord[][];    //关键字

 void Init()
 {
     strcpy(&KeyWord[][],"begin");
     strcpy(&KeyWord[][],"call");
     strcpy(&KeyWord[][],"const");
     strcpy(&KeyWord[][],"do");
     strcpy(&KeyWord[][],"end");
     strcpy(&KeyWord[][],"if");
     strcpy(&KeyWord[][],"odd");
     strcpy(&KeyWord[][],"procedure");
     strcpy(&KeyWord[][],"read");
     strcpy(&KeyWord[][],"then");
     strcpy(&KeyWord[][],"var");
     strcpy(&KeyWord[][],"while");
     strcpy(&KeyWord[][],"write");
 }

 //判断一个单词是否为关键字
 int IsKeyWord(char *word)
 {
     int i=,j=;
     while(i<=j)
     {
         int k=(i+j)/;
         if(strcmp(word,KeyWord[k])<=)
             j=k-;
         if(strcmp(word,KeyWord[k])>=)
             i=k+;
     }
     return i->j ?  : ;
 }

 //判断一个单词是否为界符
 int IsDelimiter(char word)
 {
     if(word==','||word==';'||word=='.'||word=='('||word==')')
         return ;
     return ;
 }

 //判断一个单词是否为操作符
 int IsOperator(char *word)
 {
     if(word[]=='+'||word[]=='-'||word[]=='*'||word[]=='/'||word[]=='<'||word[]=='>'||strcmp(word,":=")==||strcmp(word,">=")==||strcmp(word,"<=")==||word[]=='#'||word[]=='=')
         return ;
     return ;
 }

 //判断一个单词是否是常数
 int IsConst(char *word)
 {
     if(word[]>=''&&word[]<='')
         return ;
     return ;
 }

 //判断连个字符是否属于相同类型
 int IsSame(char f,char s)
 {
     int bf = (f>=''&&f<=''||f>='a'&&f<='z'||f>='A'&&f<='Z')?   :  ;
     int bs = (s>=''&&s<=''||s>='a'&&s<='z'||s>='A'&&s<='Z')?   :  ;
     return bf == bs;
 }

 //判断 word 的类型
 SymEnum TypeOfWord(char *word)
 {
     if(IsKeyWord(word))
         return Key;
     if(IsConst(word))
         return Const;
     if(IsOperator(word))
         return Operator;
     return Identifier;
 }

 int GetSym()
 {
     FILE *fp,*fout;
     if((fp=fopen("PL0.txt","r"))==NULL || (fout=fopen("source.txt","w+"))==NULL)
     {
         printf("Open Error!\n");
         exit();
     }
     SymEnum SYM;    //存放每个单词的类别，用内部编码形式表示；
     char word[];  //存储单词
     word[]='\0';
     int len=;      //单词长度
     char ch;
     while(fscanf(fp,"%c",&ch)!=EOF)
     {
         // ch 为空格，回车符，制表符
         if(ch==' '||ch=='\n'||ch=='\t')
         {
             // word 不为空
             if(len)
             {
                 //判断单词类型
                 SYM=TypeOfWord(word);
                 fprintf(fout,"%d %s\n",SYM,word);
                 //清空缓存区
                 len=;
                 word[len]='\0';
             }
             // word 为空，忽略 ch
         }
         else if(IsDelimiter(ch))
         {
             //word 不为空
             if(len)
             {
                 //判断单词的类型
                 SYM=TypeOfWord(word);
                 fprintf(fout,"%d %s\n",SYM,word);
                 // ch == delimiter
                 SYM=Delimiter;
                 fprintf(fout,"%d %c\n",SYM,ch);
                 //清空缓存区
                 len=;
                 word[len]='\0';
             }
             else
             {
                 //word 为空, ch 为界符
                 SYM=Delimiter;
                 fprintf(fout,"%d %c\n",SYM,ch);
                 //清空缓存区
                 len=;
                 word[len]='\0';
             }
         }
         else
         {
             if(len>)
             {
                 if(IsSame(word[len-],ch))
                 {
                     //判断 word 与 ch 是否同类型
                     word[len++]=ch;
                     word[len]='\0'; //字符串终结符
                 }
                 else
                 {
                     //判断单词类型
                     SYM=TypeOfWord(word);
                     fprintf(fout,"%d %s\n",SYM,word);
                     //清空缓存区，并把 ch 放入缓存区
                     len=;
                     word[len++]=ch;
                     word[len]='\0'; //字符串终结符
                 }
             }
             else
             {
                 word[len++]=ch;
                 word[len]='\0';
             }
         }
     }
     fclose(fp);
     fclose(fout);
     return ;
 }

 void PrintToScream()
 {
     FILE *fp;
     if((fp=fopen("source.txt","r+"))==NULL)
     {
         printf("Open File Error!\n");
         exit();
     }
     int id;
     char word[];
     printf("0-标识符 1-常数 2-关键字 3-操作符 4-界符\n");
     while(fscanf(fp,"%d %s",&id,word)!=EOF)
     {
         printf("(%d,%s)\n",id,word);
     }
     fclose(fp);
 }

 int main()
 {
     Init();
     GetSym();
     PrintToScream();
     return ;
 }