编译原理_词法分析器_C语言版_简单易懂

token[m++]=ch; break; case '+': i=35; token[m++]=ch; break; case '-':i=36; token[m++]=ch; break; case '=':i=37; token[m++]=ch; break; case '==':i=38; token[m++]=ch; break; case '*': i=15; token[m++]=ch; break; case '(': i=55; token[m++]=ch; break; case ')': i=56; token[m++]=ch; break; case ';': i=57; token[m++]=ch; break; case '#': i=0; token[m++]=ch; break; default: i=-1; break; } token[m++]='\0'; }
#include <stdio.h> #include <string.h> char ch,token[8],prog[80]; char *a[6]={"标示符","整常数","if","else","while","for"}; int p,i,sum,m,n;
panduan(); main() { p=0; printf("please input string :\n"); do { scanf("%c",&ch); prog[p++]=ch; } while(ch!='#'); p=0; do { panduan(); switch(i) { case 1:printf("(%s,%d,指向%s在符号表的入口)\n",token,i,token); break; case 2:printf("(%d,%d,指向%d在符号表的入口)\n",sum,i,sum); break; case -1:printf("error!"); default: printf("(%s,%d,-)\n",token,i); break; } } while(i!=0); printf("词法分析成功!\n"); }
panduan()
ቤተ መጻሕፍቲ ባይዱ
{ sum=0; for(m=0;m<8;m++) token[m++]=NULL; ch=prog[p++]; m=0; while((ch==' ')||(ch=='\n')) ch=prog[p++]; if(((ch<='z')&&(ch>='a'))||((ch<='Z')&&(ch>='A'))) { while(((ch<='z')&&(ch>='a'))||((ch<='Z')&&(ch>='A'))||((ch>='0')&&(ch<='9') )) { token[m++]=ch; ch=prog[p++]; } p--; i=1;//如果是字母，输出的标示类别为 for(n=0;n<6;n++) if(strcmp(token,a[n])==0) { i=n+1; break; } } else if((ch>='0')&&(ch<='9')) { while((ch>='0')&&(ch<='9')) { sum=sum*10+ch-'0'; ch=prog[p++]; } p--; i=2; } else switch(ch)// 以下为自己定义符号类的标示类别号 { case '<': i=39; token[m++]=ch; break; case '<=': i=40; token[m++]=ch; break; case '>':i=41;