asd.cpp

以上一共五个在VC环境下编写的程序

//---------------------------简单词法分析器-----------------------------
#include<iostream>
#include<stdio.h>
using namespace std;
#define MAX 50
typedef struct tnode{
	char ch[20];   //用字符的数组实现字符串的输入
	int length;    //当前字符串的长度
	int id;        //编码值
    struct tnode *next;  //用链表存储编码信息
}tnode;

char text[MAX];  //作为缓冲，存储处理后文本文件


//文本预处理---------------------------------------------------------------------
void pretreatment()
{FILE *fp,*fop;
 char filename[15],file[15],ch;
 int i=0;
 cout<<endl;
 cout<<"--------文本预处理--------"<<endl;
 cout<<"请输入文本文件的文件名:";
 cin>>filename;
 if((fp=fopen(filename,"r"))==NULL){
	 cout<<"不能打开该文件"<<endl;
	 exit(0);}
 ch=fgetc(fp);
 cout<<"请输入存储处理后文本文件的文件名:";
 cin>>file;
 if((fop=fopen(file,"w+"))==NULL){
	 cout<<"不能打开该文件"<<endl;
	 exit(0);}
 while(ch!=EOF)           
 {if((ch!=' ')&&(ch!='\n'))   //当当前字符不为空格和换行符时读入(处理空格和回车)
 {fputc(ch,fop);     
  text[i]=ch;       //将文本内容写入数组(空格和回车除外)
  i++;
 }
 ch=fgetc(fp);
 }
 fclose(fp);
 fclose(fop);

 cout<<"处理后文本文件输出＝》"<<endl;      
 cout<<"请输入存储编码文件的文件名:";
 cin>>filename;
 if((fp=fopen(filename,"r"))==NULL){
	 cout<<"不能打开该文件"<<endl;
	 exit(0);}
 cout<<"文本信息输出＝》"<<endl;
 ch=fgetc(fp);
 while(ch!=EOF)
 {putchar(ch);
  ch=fgetc(fp);
 }
 fclose(fp);
 cout<<endl;
 cout<<"--------处理完毕--------"<<endl;
 cout<<endl;
}

//建表,字符串扫描与匹配------------------------------------------------------
//新建编码表-------------------------------------------
void scanANDmatch()
{char *r,*s,*t,*c,*w;
 struct tnode *p,*q,*l;
 int i,n,leng=0;
 cout<<endl;
 cout<<"--------建表&扫描&匹配--------"<<endl;
 cout<<"-----编码信息构造-----"<<endl;
 cout<<"请输入编码表节点个数：";
 cin>>n;
 p=(struct tnode *)malloc(sizeof(struct tnode));
 p->next=NULL;
 q=p;
 l=p;
 cout<<"请输入各节点单词及其编码值："<<endl;
 for(i=1;i<=n;i++)
 {cout<<"请输入第"<<i<<"个单词内容：";
  cin>>p->ch;
  c=p->ch;
  while(*c!=NULL)    //计算当前字符串的长度(一个曾经的思维过程，此处无用但保留)
  {leng++;
   c++;
  }
  p->length=leng;   //将当前字符串长存入结构体
  leng=0;
  cout<<"请输入其编码值：";
  cin>>p->id;
 //cout<<p->ch<<endl;
  p=(struct tnode *)malloc(sizeof(struct tnode));  
  p->next=q->next;q->next=p;
  q=p;
 }                          //生成不带头节点的链表
 cout<<"-----构造编码表成功-----"<<endl<<endl;

//字符串扫描与匹配-----------------------------------------
 cout<<"Token串输出为："<<endl;
 p=l;                      //恢复链表起始地址指针
 s=text;    //定义指针b指向数组起始地址
 t=p->ch;   //定义指针c指向当前单词的起始地址
 r=s;  //存储数组首地址指针，便于恢复

to: while(*s!=NULL)              //注意:这里不要写为while(*s!=' '),否则将进入死循环
{if((*s>='a' && *s<='z')&&(*(s+1)<='a' || *(s+1)>='z'))   //判定是否为变量 
 {p=l;
  while(p->id!=1)   //设定变量编码值均为1
  {p=p->next;}
  cout<<"("<<*s<<","<<p->id<<")"<<endl;
  p=l;  //恢复指针p
  s=s+1;  //数组指针前移一位
 }
 if(*s>='0' && *s<='9')                        //判定是否为常量
 {p=l;
  while(p->id!=2)   //设定常量编码值均为2
  {p=p->next;}
  cout<<"("<<*s<<","<<p->id<<")"<<endl;
  p=l;   
  s=s+1;
 }
 w=s;  //存储当前数组指针地址
 while(*s!=NULL){                    //关键字及界符输出
	 while(*s==*t){
		 if((*s==':')&&(*(s+1)=='='))   //为判定是否为":="做超前搜索
		 {//p=l;
		  //t=p->ch;
		  while(*(t+1)!='=')
		  {p=p->next; 
		   t=p->ch;
		  }
          if((*t==':')&&(*(t+1)=='=')){
		  cout<<"("<<p->ch<<","<<p->id<<")"<<endl;
		  p=l;
		  t=p->ch;
		  s=s+2;   //数组指针前移两位 
		  goto to;
		  }
		  }
         s++;
		 t++;
		 if(*t==NULL){           //匹配，输出关键字或界符与其的编码值
			 cout<<"("<<p->ch<<","<<p->id<<")"<<endl;
			 p=l;
			 t=p->ch;
			 goto to; //while语句过多，只能采用goto了
		     }
	 }
	if(*s!=*t) {s=w; p=p->next; t=p->ch;}  //未匹配上，回到上次s的位置，指针p前移，继续扫描	 
 }
}
 cout<<endl;
 cout<<"--------操作完毕--------"<<endl<<endl;
}


void main()
{char w;
 int k=1;
 cout<<endl;
 cout<<"     **********************"<<endl;
 cout<<"        *简单词法分析器*"<<endl;
 cout<<"     **********************"<<endl;
 cout<<"              ------计0306,曾庚卓,20032969"<<endl<<endl;
 cout<<"---------------目录---------------"<<endl<<endl;
 cout<<"  1-----------文本预处理"<<endl;
 cout<<"  2-----------建表&扫描&匹配"<<endl;
 cout<<"  3-----------退出"<<endl<<endl;

do
{
	cout<<"请按键选择：";
cin>>w;
switch(w)
{
 case '1':pretreatment();break;	
 case '2':scanANDmatch();break;
}}
	while(w!='3');
cout<<"---------------结束任务!---------------"<<endl<<endl;
}