正商物业电话:学习编译原理时做的词法分析器的

学习编译原理时做的词法分析器
作者：程红秀    文章来源：http://www.59hao.com/chx    点击数：     更新时间：2005-5-24

主要的代码如下（这里给出的是命令行代码，稍加修改就可以做成上面的界面了），具体请参考源文件：
#include
#include
#include
#include
#define  MAX 18   //分析表的最大容量
#define  MAXBUF 255
char  ch =‘ ‘;   // 存放读入当前的输入字符
int lineno;
struct reserve   //关键字
{
char lexptr[MAXBUF];
int token;
};
struct reserve symtable[MAX];
char * str[]={"program","input","output","begin","end","var","integer","real","for","to","if","then","else","do","while","write","array","proceure" };
void init()     //对符号表进行初始化
{
for( int j=0; j<18; j++)
{
strcpy(symtable[j].lexptr,str[j]);
symtable[j].token=j+3;
}
}
int search(char *temp)
{
for(int i=0; i
void analyse(FILE *fpin,FILE *fpout)    //分析程序
{
char arr[MAXBUF];
int i=0;
int j=0;
while((ch=fgetc(fpin))!=EOF)    //读入字符判断，空格、字母、数字、界符
{
if(ch==‘ ‘||ch==‘\t‘)
{
}
else if(ch==‘\n‘)    //如果是换行符，则行号加1
{
lineno++;
}
else if(isdigit(ch))   //如果是数字
{
while(isdigit(ch))   //判断和读取数字
{
arr[j]=ch;
j++;
ch=fgetc(fpin);
}
arr[j]=‘\0‘;
j=0;
fseek(fpin,-1L,SEEK_CUR);
fprintf(fpout,"%s\t%d\n",arr,2) ;
}
else if (isalpha(ch))  //如果是字母
{
while(isalpha(ch)||isdigit(ch))
{
arr[j]=ch;
j++;
ch=fgetc(fpin);
}
fseek(fpin,-1L,SEEK_CUR);
arr[j]=‘\0‘;
j=0;
if (search(arr)) //如果是关键字
{
fprintf(fpout,"%s\t%d\n",arr,search(arr));
}
else
fprintf(fpout,"%s\t%d\n",arr,1); //普通标志符
}
else if(ch==‘:‘)
{
ch=fgetc(fpin);
if(ch==‘=‘)
{
fprintf(fpout,"%s\t%d\n",":=",29);    //如果是 :=
}
else
{
fprintf(fpout,"%s\t%d\n",":",30);   //如果是 :
fseek(fpin,-1L,SEEK_CUR);
}
}
else if (ch==‘>‘)
{
ch=fgetc(fpin);
if(ch==‘=‘)    //如果是 >=
{
fprintf(fpout,"%s\t%d\n",">=",32);
}
else
{
fprintf(fpout,"%s\t%d\n",">",31);  //如果是 >
fseek(fpin,-1L,SEEK_CUR);
}
}
else if(ch==‘<‘)
{
ch=fgetc(fpin);
if(ch==‘>‘)
{
fprintf(fpout,"%s\t%d\n","<>",35);  // 如果是 <>
}
else if(ch==‘=‘)
{
fprintf(fpout,"%s\t%d\n","<=",34);   //如果是 <=
}
else
{
fprintf(fpout,"%s\t%d\n","<",33);   //如果是 <
fseek(fpin,-1L,SEEK_CUR);
}
}
else if(ch==‘/‘)
{
ch=fgetc(fpin);
if(ch==‘*‘)
{
ch=fgetc(fpin);
s:
while(ch!=‘*‘)
{
ch=fgetc(fpin);
}
while(ch==‘*‘)
{
ch=fgetc(fpin);
while(ch!=‘/‘)
{
goto s;   //如果是注释 /*  */
}
}
}
else if(ch==‘/‘)
{
ch=fgetc(fpin);
while(ch!=‘\n‘)
{
ch=fgetc(fpin);   //如果是注释 //
}
}
else
{
fprintf(fpout,"%s\t%d\n","/",24);
fseek(fpin,-1L,SEEK_CUR);
}
}
else if(ch==‘+‘)
{
fprintf(fpout,"%s\t%d\n","+",21);
}
else if(ch==‘-‘)
{
fprintf(fpout,"%s\t%d\n","-",22);
}
else if(ch==‘*‘)
{
fprintf(fpout,"%s\t%d\n","*",23);
}
else if(ch==‘(‘)
{
fprintf(fpout,"%s\t%d\n","(",25);
}
else if(ch==‘)‘)
{
fprintf(fpout,"%s\t%d\n",")",26);
}
else if(ch==‘[‘)
{
fprintf(fpout,"%s\t%d\n","[",27);
}
else if(ch==‘]‘)
{
fprintf(fpout,"%s\t%d\n","]",28);
}
else if(ch==‘.‘)
{
fprintf(fpout,"%s\t%d\n",".",39);
}
else if(ch==‘;‘)
{
fprintf(fpout,"%s\t%d\n",";",36);
}
else if(ch==‘=‘)
{
fprintf(fpout,"%s\t%d\n","=",38);
}
else if(ch==‘,‘)
{
fprintf(fpout,"%s\t%d\n",",",40);
}
else fprintf(fpout,"无法识别的字符 %c\n",ch)  ;
}
}
void main()
{
printf("***************************词法分析器*************************\n\n\n");
printf("直接输入源代码请按1，从文件中读入源代码请按2 \n") ;
char filenamein[10];
char filenameout[10];
printf("请输入源文件名：\n");
scanf("%s",filenamein);
printf("请输入保存词法分析结果的文件名：\n");
scanf("%s",filenameout);
FILE* fpin=fopen(filenamein,"r");
FILE* fpout=fopen(filenameout,"w");
init();
analyse(fpin,fpout);
fclose(fpin);
fclose(fpout);
_getch();
}