cifafenxiqi.c

编译原理语法&词法分析器（附带实验报告）希望对大家有用

#include<stdio.h>
#include<string.h>

char prog[80],token[6];
char ch;
int syn,p,m,n,sum;
char * rwtab[6]={"begin","if","then","while","do","end"};
main()
{
 p=0;
 printf("\nplease intput string:");
do
{
 ch=getchar();
 prog[p++]=ch;
}while(ch!='#');
p=0;
do
{
 scaner();
 switch(syn)
 {
  case 11:printf("(%d,%d)",syn,sum);break;
  case -1:printf("input error\n");  break;
  default:printf("(%d,%s)",syn,token);
 }
}while(syn!=0);
getch();
}

/*词法扫描程序：*/
scaner()
{
 for(n=0;n<8;n++)
  token[n]=NULL;
  m=0;
  ch=prog[p++];
  while(ch==' ')ch=prog[p++];
  if((ch<='z'&&ch>='a')||(ch<='Z'&&ch>='A'))
  {
   while((ch<='z'&&ch>='a')||(ch<='Z'&&ch>='A')||(ch<='9'&&ch>='0'))
   {
    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)
       {
        syn=n+1;
        break;
        }
    }
   else
       if((ch<='9'&&ch>='0'))
         {
          sum=0;
          while((ch<='9'&&ch>='0'))
          {
           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;
                    }
                    else
                        if(ch=='=')
                        {
                         syn=22;
                         token[m++]=ch;
                         }
                         else
                         {
                          syn=20;
                          ch=prog[--p];
                          }
          break;
          case '>':token[m++]=ch;
                   ch=prog[p++];
                   if(ch=='=')
                   {
                   syn=24;
                   token[m++]=ch;
                    }
                   else
                   {
                    syn=23;
                    ch=prog[--p];
                    }
          break;
          case ':':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=18;token[0]=ch;break;
          case '<>':syn=21;token[0]=ch;break;
          case '<=':syn=22;token[0]=ch;break;
          case '>=':syn=24;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;
          }
      }