cifafenxiqi.cpp

编译原理课程设计报告＋词法分析器（C++)源代码 逐个读入源程序字符并按照构词规则切分成一系列单词。单词是语言中具有独立意义的最小单位包括保留字、标识符、运算符、标点符号和常量等。

#include <iostream.h>
#include <fstream.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#include <conio.h>

#define  MAX 18  
#define  MAXBUF 255 
char  ch =' ';           //读下一个字符
int linenum;              //行数计数


/*关键字存储结构*/
struct reserve
{
 char lexptr[MAXBUF];
 int token;              //关键字
};

struct reserve symtable[MAX];//行数
char * str[]={"begin","void","main","program","int","char","real","for",
              "to","if","then","else","do","while","var","end","input","output"};
// 以上关键字符号依次的种别号从3～20


/*关键字的定义*/
void init()
{
 for( int j=0; j<18; j++)
 { 
  strcpy(symtable[j].lexptr,str[j]);
  symtable[j].token=j+3;       //关键字种别码从3开始
 }
}



/*查找符合的关键字*/
int search(char *temp)
{
 for(unsigned int i=0;i < 18;i++)
 {
	 if(!strcmp(symtable[i].lexptr ,temp))
		return  symtable[i].token;
 
 }
 return 0;
}     


/*读取源文件后，做词法分析，最后将结果输出在指定文件中*/
void analyse(FILE *fpin,FILE *fpout)
{
 char arr[MAXBUF];        //词法分析缓冲区
 int i=0;
 int j=0;
 
 while((ch=fgetc(fpin))!=EOF)
 {
  if(ch==' '||ch=='\t')
  {
   
  }
  else if(ch=='\n')
  {  
   linenum++;
  }
  else if(isdigit(ch))    //判断字符是否是数字字符
  { 
   while(isdigit(ch))
   { 
    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) ;  //是，就将数字字符及种别码2输出
  }
  else if (isalpha(ch))
  {
   while(isalpha(ch)||isdigit(ch))	  //判断字符是否是字母字符
   {
    arr[j]=ch;
    j++;
    ch=fgetc(fpin);
   }
   fseek(fpin,-1L,SEEK_CUR);
   arr[j]='\0';
   j=0;
   if (search(arr))
   {
    fprintf(fpout,"%s\t%d\n",arr,search(arr));
   }
   else  
    fprintf(fpout,"%s\t%d\n",arr,1); //是，就将字母字符及种别码1输出
  }
  else if(ch==':')                   //判断字符是否是运算符和界符
  {
   ch=fgetc(fpin);
   if(ch=='=') 
   {
    fprintf(fpout,"%s\t%d\n",":=",29);
   }
   else
   {
    fprintf(fpout,"%s\t%d\n",":",30);
    fseek(fpin,-1L,SEEK_CUR);
   }
  }
  else if (ch=='>')
  {
   ch=fgetc(fpin);
   if(ch=='=')
   {
    fprintf(fpout,"%s\t%d\n",">=",32);
   }
   else
   {
    fprintf(fpout,"%s\t%d\n",">",31);
    fseek(fpin,-1L,SEEK_CUR);
   }
  }
  else if(ch=='<')
  { 
   ch=fgetc(fpin);
   if(ch=='>')
   {
    fprintf(fpout,"%s\t%d\n","<>",35);
   }
   else if(ch=='=')
   {
    fprintf(fpout,"%s\t%d\n","<=",34);
   }
   else 
   {
    fprintf(fpout,"%s\t%d\n","<",33);
    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;
     }
    }
   }
   else if(ch=='/')
   {
    ch=fgetc(fpin);
    while(ch!='\n')
    {
     ch=fgetc(fpin);
    }
   }
   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 if(ch=='"')
  {
   fprintf(fpout,"%s\t%d\n","\"",41);
  }
   else if(ch=='{')
  {
   fprintf(fpout,"%s\t%d\n","{",42);
  }
    else if(ch=='}')
  {
   fprintf(fpout,"%s\t%d\n","}",43);
  }
  else fprintf(fpout,"无法识别的字符 %c\n",ch)  ;
   }
} 


void main()
{
 printf("***************************词法分析器*************************\n\n\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(请注明文件格式)：\n");
 scanf("%s",filenameout);
 FILE* fpin=fopen(filenamein,"r");     //将源文件以只读的方式打开
 FILE* fpout=fopen(filenameout,"w");   
 init();
 analyse(fpin,fpout);
 fclose(fpin);                        //关闭文件
 fclose(fpout);
 
}