/*
*词法分析程序
*Code by:Prudence
*QQ:95678648
*/
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <malloc.h>
#define MAXLENGHT 80 //定义标志符的最大程度
#define SIZE 5 //关键字表大小
char word[SIZE][MAXLENGHT]={"begin","else","end","if","then"};
char cn[MAXLENGHT];//存放解析过程中的字符，做为临时变量使用
struct WordTable //为链表结构，存放词法分析过程中单词
{
int type;//1为关键字，2为标志符，3为数字，4为运算符
union
{
long value;
char name[MAXLENGHT];
}k;
WordTable *next;
}wt;
void InsertLastNode(char *name,int type,long value)
{
WordTable *n=&wt;
while(n->next!=NULL)
n=n->next;
WordTable *newp=(WordTable *)malloc(sizeof(WordTable));
newp->type=type;
newp->next=NULL;
if(type!=3)
strcpy(newp->k.name,cn);
else
newp->k.value=value;
n->next=newp;
}
void getword()
{
int k,len=0,mid;
int low,high;//二分法查找关键字表
char c;
while((c=getchar())!='#')
{
if(isalpha(c)||c=='_')//关键字
{
k=0;
memset(cn,0,MAXLENGHT);
do
{
cn[k++]=c;
len++;
c=getchar();
}while(isalpha(c) || isdigit(c) ||c=='_');
ungetc(c,stdin);
if(len>MAXLENGHT)
{
printf("变量定义太长\n");
exit(1);
}
low=0;
high=SIZE;
while(low<=high)
{
mid=(low+high)/2;
if(strcmp(cn,word[mid])<0)
high=mid-1;
else if(strcmp(cn,word[mid])>0)
low=mid+1;
else
break;
}
if(low>high)
{
InsertLastNode(cn,2,0);
}
else
{
InsertLastNode(cn,1,0);
}
}
else if(isdigit(c))//数字
{
long value=0;
do
{
value=value*10+c-'0';
}while(isdigit(c=getchar()));
ungetc(c,stdin);
InsertLastNode(NULL,3,value);
}
else//特殊字符
{
k=0;
memset(cn,0,MAXLENGHT);
if(c=='<')
{
cn[k++]=c;
c=getchar();
if(c=='='||c=='>')
{
cn[k++]=c;
c=getchar();
}
ungetc(c,stdin);
InsertLastNode(cn,4,0);
}
else if(c=='>')
{
cn[k++]=c;
c=getchar();
if(c=='=')
{
cn[k++]=c;
c=getchar();
}
ungetc(c,stdin);
InsertLastNode(cn,4,0);
}
else if(c=='=')
{
cn[k++]=c;
InsertLastNode(cn,4,0);
}
else if(c=='+')
{
cn[k++]=c;
InsertLastNode(cn,4,0);
}
else if(c=='-')
{
cn[k++]=c;
InsertLastNode(cn,4,0);
}
else if(c=='*')
{
cn[k++]=c;
InsertLastNode(cn,4,0);
}
else if(c=='/')
{
cn[k++]=c;
InsertLastNode(cn,4,0);
}
else
{
if(c==' ' || c=='\t' ||c==10 || c==13)
continue;
printf("不能识别的符号\n");
exit(1);
}
}
}
}
void output()
{
WordTable *p=wt.next;
while(p!=NULL)
{
switch(p->type)
{
case 1:
printf("(%s,关键字)\n",p->k.name);
break;
case 2:
printf("(%s,标志符)\n",p->k.name);
break;
case 3:
printf("(%d,数字)\n",p->k.value);
break;
case 4:
printf("(%s,运算符)\n",p->k.name);
break;
}
p=p->next;
}
}
void main()
{
printf("********************************词法分析程序***********************************\n");
printf(" Code by:Prudence \n");
printf(" QQ:95678648 \n");
printf("*********************************以#号结束*************************************\n");
getword();
printf("*******************************************************************************\n");
output();
}
阿里云助力开发者！2核2G 3M带宽不限流量！6.18限时价，开
发者可享99元/年，续费同价！
