词法分析程序

  1 #include <stdio.h> 
  2 #include <string.h>  
  3 char prog[30],token[5],ch; 
  4 int syn,p,m,n,sum;  
  5 char *rwtab[6]={"begin","if","then","while","do","end"}; 
  6 scaner(); 
  7 main() 
  8 {p=0;  
  9  printf("请输入你要分析的程序（按“#”结束）:"); 
 10  do{  
 11      scanf("%c",&ch); 
 12      prog[p++]=ch; 
 13  }while(ch!=‘#‘); 
 14    p=0; 
 15  do{  scaner(); 
 16    switch(syn)  
 17    {    case 11:printf("( %-10d%5d )\n",sum,syn); 
 18         break;  
 19         case -1:printf("you have input a wrong string\n"); 
 20         getch(); 
 21         exit(0);  
 22         default: printf("( %-10s%5d )\n",token,syn); 
 23         break; 
 24 }  
 25 }while(syn!=0); 
 26   getch();  
 27 } 
 28    scaner() 
 29    {  sum=0;  
 30     for(m=0;m<8;m++)token[m++]=NULL; 
 31      ch=prog[p++]; 
 32      m=0;  
 33  while((ch==‘ ‘)||(ch==‘\n‘))ch=prog[p++];  
 34  if(((ch<=‘z‘)&&(ch>=‘a‘))||((ch<=‘Z‘)&&(ch>=‘A‘)))  
 35  { 
 36      while(((ch<=‘z‘)&&(ch>=‘a‘))||((ch<=‘Z‘)&&(ch>=‘A‘))||((ch>=‘0‘)&&(ch<=‘9‘))) 
 37  {
 38          token[m++]=ch; 
 39          ch=prog[p++]; 
 40 }  
 41     p--; 
 42     syn=10;
 43     for(n=0;n<6;n++)  
 44     if(strcmp(token,rwtab[n])==0) 
 45     {  syn=n+1; 
 46        break;  
 47     } 
 48  }  
 49     else if((ch>=‘0‘)&&(ch<=‘9‘)) 
 50     {  while((ch>=‘0‘)&&(ch<=‘9‘)) 
 51     {  sum=sum*10+ch-‘0‘; 
 52         ch=prog[p++]; 
 53     } 
 54       p--;  
 55       syn=11; 
 56     }  
 57      else switch(ch)  
 58      {   case ‘<‘:token[m++]=ch; 
 59     ch=prog[p++]; 
 60 if(ch==‘=‘) 
 61 { 
 62     syn=22;  
 63     token[m++]=ch; 
 64 }  
 65 else  
 66 { 
 67    syn=20;  
 68    p--;  
 69 } 
 70  break;  
 71     case ‘>‘:token[m++]=ch; 
 72     ch=prog[p++]; 
 73     if(ch==‘=‘) 
 74     {   syn=24;  
 75         token[m++]=ch; 
 76  } 
 77  else  
 78  {    syn=23; 
 79        p--; 
 80  } 
 81  break;  
 82        case ‘+‘: token[m++]=ch; 
 83        ch=prog[p++]; 
 84 if(ch==‘+‘) 
 85 {    syn=17;  
 86      token[m++]=ch; 
 87  }  
 88 else  
 89 {     syn=13; 
 90       p--;  
 91 } 
 92 break; 
 93         case ‘-‘:token[m++]=ch;  
 94            ch=prog[p++]; 
 95     if(ch==‘-‘) 
 96     {        syn=29;  
 97          token[m++]=ch; 
 98     }  
 99         else  
100         {       syn=14; 
101                 p--; 
102         }  
103           break; 
104        case ‘!‘:ch=prog[p++];
105     if(ch==‘=‘) 
106     { syn=21;  
107       token[m++]=ch; 
108     } 
109     else 
110     { syn=31;
111        p--;
112     }  
113       break; 
114       case ‘=‘:token[m++]=ch; 
115           ch=prog[p++];
116            if(ch==‘=‘) 
117            { syn=25;  
118               token[m++]=ch;  
119            } 
120       else 
121       { syn=18; 
122          p--; 
123       } 
124         break;
125         case ‘*‘: syn=15;  
126           token[m++]=ch;  
127           break; 
128         case ‘/‘: syn=16;  
129            token[m++]=ch; 
130            break; 
131         case ‘(‘: syn=27;
132             token[m++]=ch; 
133             break; 
134         case ‘)‘: syn=28;  
135             token[m++]=ch; 
136             break; 
137         case ‘{‘: syn=5;  
138             token[m++]=ch; 
139             break; 
140         case ‘}‘: syn=6;
141             token[m++]=ch; 
142             break; 
143         case ‘;‘: syn=26;  
144             token[m++]=ch; 
145             break; 
146         case ‘\"‘: syn=30;  
147             token[m++]=ch; 
148              break; 
149         case ‘#‘: syn=0;  
150             token[m++]=ch; 
151              break; 
152         case ‘:‘:syn=17;  
153             token[m++]=ch;  
154              break;
155         default: syn=-1; 
156              break; 
157 }
158 token[m++]=‘\0‘; 
159 }