实验1.cpp

1 掌握手工生成词法分析器的方法

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <malloc.h>
#include <conio.h>
#define NULL 0
FILE *fp;
char ch;
char *keyword[33]={"auto","break","case","char","const","continue","default","do","double", 
"else","enum","extern","float","for","goto","if","int","long","register", 
"return","short","signed","sizeof","static","struct","switch","typedef", 
"union","unsigned","void","volatile","while","main"};
char *operatornum[]={"+","-","*","/","++","--"};
char *comparison[7]={"<","<=","=",">",">=","<>","=="};
char *interpunction[8]={",",";",":=",".","(",")","{","}"};
//////////////////////////////////////////////////////////////////////////////////////////
bool search(char searchstr[],int wordtype)
{
int i;
switch (wordtype)
{
case 1:for(i=0;i<=32;i++)
     {
      if(strcmp(keyword[i],searchstr)==0)
       return(true);
      
     }
case 2:{
  for(i=0;i<=5;i++)
  {
   if(strcmp(operatornum[i],searchstr)==0)
    return(true);
  }
  break;
     }
case 3: {
	for(i=0;i<=6;i++)
   {
    if(strcmp(comparison[i],searchstr)==0)
     return(true);
	}
	break;
   }
case 4: for(i=0;i<=7;i++)
   {
    if(strcmp(interpunction[i],searchstr)==0)
     return(true);
   }
  

}
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("<%s,关键字>\n",letter);

}
else
{
  printf("<%s,自定义变量>\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("<%s,数字>\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("<%s,算数运算符>\n",other);
else 
if (search(other,3))
   printf("<%s,关系运算符号>\n",other);
else
if (search(other,4))
    printf("<%s,分隔符号>\n",other);
else 
   printf("错误！非法字符：%s\n",other);
u: return (ch);
}

/////////////////////////////////////////////////////////////////////////////////////////////
void main ()
{
char str,c;
printf("**********************************词法分析器************************************\n");
if ((fp=fopen("源程序.txt","r"))==NULL)
  printf("源程序无法打开！\n");
else
{
  str =fgetc(fp);
  while (str!=EOF)
  {
   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();


}