cifa.cpp

递归子程序法：对应每个非终结符语法单元编一个独立的处理过程（或子程序）。语法分析从读入第一个单词开始

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include <ctype.h>
#include <conio.h>
#define NULL 0
FILE *fp;
char ch;
char *keyword[8]={"do","begin","else","end","if","then","var","while"};
char *operatornum[4]={"+","-","*","/"};
char *comparison[6]={"<","<=","=",">",">=","<>"};
char *interpunction[11]={",",";",":",":=",".","(",")","{","}","[","]"};
bool search(char searchstr[],int wordtype)
{
 int i;
 switch (wordtype)
 {
 case 1:for(i=0;i<=7;i++)
     {
      if(strcmp(keyword[i],searchstr)==0)
       return(true);
      
     }
 case 2:{
  for(i=0;i<=3;i++)
  {
   if(strcmp(operatornum[i],searchstr)==0)
    return(true);
  }break;

     }
 case 3: {for(i=0;i<=5;i++)
   {
    if(strcmp(comparison[i],searchstr)==0)
     return(true); 
		 } break;
		 }
 case 4: {for(i=0;i<=10;i++)

   {
    if(strcmp(interpunction[i],searchstr)==0)
     return(true);
   }
   break;}
 }
 return(false);
}

char letterprocess (char ch)//字母处理函数
{
 int i=-1;
 char letter[20];
 while (isalnum(ch)!=0)
 {
  letter[++i]=ch;
  ch=fgetc(fp);
 };
 letter[i+1]='\0';
 if (search(letter,1))
 {
  printf("<keyword：%s>\n",letter);
 }
 else
 {
  printf("<indentifier：%s>\n",letter);
 }
 return(ch);
}

char numberprocess(char ch)//数字处理程序
{
 int i=-1;
 char num[20];
 while (isdigit(ch)!=0)
 {
  num[++i]=ch;
  ch=fgetc(fp);
 }
 if(isalpha(ch)!=0)
 {
  while(isspace(ch)==0)
  {
   num[++i]=ch;
            ch=fgetc(fp);
  }
  num[i+1]='\0';
  printf("错误！非法标识符：%s\n",num);
  goto u;
 }
 num[i+1]='\0';
    printf("<num：%s>\n",num);
   u: return(ch);
}
char otherprocess(char ch)
{
 int i=-1;
 char other[20];
 if (isspace(ch)!=0)
 {
  ch=fgetc(fp);
  goto u;
 }
 while ((isspace(ch)==0)&&(isalnum(ch)==0))
 {
  other[++i]=ch;
  ch=fgetc(fp);
 }
 other[i+1]='\0';
 if (search(other,2))
 { printf("<operatornum：%s>\n",other);}
 else if (search(other,3))
 {printf("<comparison：%s>\n",other);}
 else if (search(other,4))
 {   printf("<interpunction：%s>\n",other);}
   else 
   { printf("错误！非法字符：%s\n",other);}
u: return (ch);
}

void main ()
{
 char str,c;
 int i=-1;
 char zhushi[200];

 printf("**********************************词法分析器************************************\n");
 if ((fp=fopen("ex.txt","r"))==NULL)
  printf("文件无法打开！\n");
 else
 {
  str =fgetc(fp);
  while (str!=EOF)
  {
	  if(str=='/') //判断注释
	  {           
         str=fgetc(fp);
		   if(str=='*')
			{              
			  str=fgetc(fp);
		    while(str!='*')
			{   zhushi[++i]=str;
			    str=fgetc(fp);}
			    zhushi[i+1]='\0';
				str=fgetc(fp);
				if(str=='/')
			{			 
  		printf("注释：/*%s*/\n",zhushi);}
           else
				str=fgetc(fp);
		   }
	}
   else
   {
    if (isalpha(str)!=0)
    str=letterprocess(str);
   else
   {
    if (isdigit(str)!=0)
     str=numberprocess(str);
    else
     str=otherprocess(str);
   }
   }
  };
  printf("词法分析结束，谢谢使用！\n");
  printf("点任意键退出!\n");
 }
   c=getch();
}