编译原理的词法分析.doc

#include"stdio.h"/*定义I/O库所用的某些宏和变量*/
#include"string.h"/*定义字符串库函数*/
#include"conio.h"/*提供有关屏幕窗口操作函数*/
#include"ctype.h"/*分类函数*/
charprog[80]={'\0'},
token[8];/*存放构成单词符号的字符串*/
charch;
intsyn,/*存放单词字符的种别码*/
n,
sum,/*存放整数型单词*/
m,p;/*p是缓冲区prog的指针，m是token的指针*/
char*rwtab[6]={"begin","if","then","while","do","end"};
voidscaner(){
m=0;
sum=0;
for(n=0;n<8;n++)
token[n]='\0';
ch=prog[p++];
while(ch=='')
ch=prog[p++];
if(isalpha(ch))/*ch为字母字符*/{
while(isalpha(ch)||isdigit(ch))/*ch为字母字符或者数字字符*/{
token[m++]=ch;
ch=prog[p++];}
token[m++]='\0';
ch=prog[p--];
syn=10;
for(n=0;n<6;n++)
if(strcmp(token,rwtab[n])==0)/*字符串的比较*/{
syn=n+1;
break;}}
else
if(isdigit(ch))/*ch是数字字符*/{
while(isdigit(ch))/*ch是数字字符*/{
sum=sum*10+ch-'0';
ch=prog[p++];}
ch=prog[p--];
syn=11;}
else
switch(ch){
case'<':m=0;token[m++]=ch;ch=prog[p++];
if(ch=='>'){
syn=21;
token[m++]=ch;}
elseif(ch=='='){
syn=22;
token[m++]=ch;}
else{
syn=20;
ch=prog[p--];}
break;
case'>':m=0;token[m++]=ch;ch=prog[p++];
if(ch=='='){
syn=24;
token[m++]=ch;}
else{
syn=23;
ch=prog[p--];}
break;
case':':m=0;token[m++]=ch;ch=prog[p++];
if(ch=='='){
syn=18;
token[m++]=ch;}

else{
syn=17;
ch=prog[p--];}
break;
case'+':syn=13;token[0]=ch;break;
case'-':syn=14;token[0]=ch;break;
case'*':syn=15;token[0]=ch;break;
case'/':syn=16;token[0]=ch;break;
case'=':syn=25;token[0]=ch;break;
case';':syn=26;token[0]=ch;break;
case'(':syn=27;token[0]=ch;break;
case')':syn=28;token[0]=ch;break;
case'#':syn=0;token[0]=ch;break;
default:syn=-1;}}
main()
{
printf("\n\nThesignificanceofthefigures:\n"
"1.figures1to6saidKeyword\n"
"2.figures10and11saidOtherindicators\n"
"3.figures13to28saidOperators\n");

p=0;

printf("\npleaseinputstring:\n");
do{
ch=getchar();
prog[p++]=ch;
}while(ch!='#');

p=0;

do{
scaner();
switch(syn){
case11:printf("(%d,%d)\n",syn,sum);break;
case-1:printf("\nERROR;\n");break;
default:printf("(%d,%s)\n",syn,token);
}
}while(syn!=0);

getch();
}
对源程序beginx:=9:ifx>9thenx:=2*x+1/3;end#