0917 实验一 词法分析程序

0917 实验一 词法分析程序
 1 #include <stdio.h>  
  2 #include <string.h>  
  3   
  4 char prog[80],token[8],ch;  
  5 int syn,p,m,n,sum;  
  6 char *rwtab[6]={"begin","if","then","while","do","end"};  
  7    
  8 void scaner(void);  
  9   
 10 main()  
 11 {  
 12     p=0;  
 13     printf("\n Please input the source code:\n");  
 14       
 15     do{  
 16             scanf("%c",&ch);  
 17             prog[p++]=ch;  
 18     }while(ch!=‘#‘);  
 19       
 20     p=0;  
 21     do{  
 22             scaner();  
 23             switch(syn)  
 24             {  
 25                 case 11:  
 26                     printf("( %d,%d )\n",syn,sum); 
 27                 break;  
 28                   
 29                 case -1:  
 30                     printf("you have input a wrong string\n");  
 31                     //getch();  
 32                     return 0;  
 33                 break;  
 34                   
 35                 default:   
 36                 printf("( %d,%s )\n",syn,token);  
 37                 break;  
 38             }  
 39         }while(syn!=0);  
 40     //getch();  
 41                     printf(" Over.\n");
 42  }  
 43   
 44 void scaner(void)  
 45 {    
 46     sum=0;  
 47       
 48     for(m=0;m<8;m++)  
 49         token[m++]= NULL;  
 50       
 51         ch=prog[p++];  
 52         m=0;  
 53           
 54     while((ch==‘ ‘)||(ch==‘\n‘))  
 55         ch=prog[p++];  
 56       
 57     if(((ch<=‘z‘)&&(ch>=‘a‘))||((ch<=‘Z‘)&&(ch>=‘A‘)))  
 58      {   
 59         while(((ch<=‘z‘)&&(ch>=‘a‘))||((ch<=‘Z‘)&&(ch>=‘A‘))||((ch>=‘0‘)&&(ch<=‘9‘)))  
 60         {  
 61             token[m++]=ch;  
 62             ch=prog[p++];  
 63         }  
 64           
 65         p--;  
 66         syn=10;  
 67   
 68         for(n=0;n<6;n++)  
 69         if(strcmp(token,rwtab[n])==0)  
 70         {   
 71             syn=n+1;  
 72             break;  
 73         }  
 74      }  
 75      else if((ch>=‘0‘)&&(ch<=‘9‘))  
 76      {   
 77         while((ch>=‘0‘)&&(ch<=‘9‘))  
 78         {  
 79             sum=sum*10+ch-‘0‘;  
 80             ch=prog[p++];  
 81         }  
 82         p--;  
 83         syn=11;  
 84     }  
 85     else   
 86     {  
 87         switch(ch)  
 88         {  
 89         case ‘<‘:  
 90             token[m++]=ch;  
 91             ch=prog[p++];  
 92             if(ch==‘=‘)  
 93             {   
 94                 syn=22;  
 95                 token[m++]=ch;  
 96             }  
 97             else  
 98             {    
 99                 syn=20;  
100                 p--;  
101             }  
102         break;  
103   
104         case ‘>‘:  
105             token[m++]=ch;  
106             ch=prog[p++];  
107             if(ch==‘=‘)  
108             {  
109                 syn=24;  
110                 token[m++]=ch;  
111             }  
112             else  
113             {   
114                 syn=23;  
115                 p--;  
116             }  
117         break;  
118   
119         case ‘+‘:  
120             token[m++]=ch;  
121             ch=prog[p++];  
122             if(ch==‘+‘)  
123             {  
124                 syn=17;  
125                 token[m++]=ch;  
126             }  
127             else  
128             {  
129                 syn=13;  
130                 p--;  
131             }  
132         break;  
133   
134         case ‘-‘:  
135             token[m++]=ch;  
136             ch=prog[p++];  
137             if(ch==‘-‘)  
138             {  
139                 syn=29;  
140                 token[m++]=ch;  
141             }  
142             else  
143             {   
144                 syn=14;  
145                 p--;  
146             }  
147         break;  
148   
149         case ‘=‘:  
150             token[m++]=ch;  
151             ch=prog[p++];  
152             if(ch==‘=‘)  
153             {  
154                 syn=25;  
155                 token[m++]=ch;  
156             }  
157             else  
158             {  
159                 syn=18;  
160                 p--;  
161             }  
162         break;  
163   
164         case ‘*‘: syn=15;token[m++]=ch; break;
165         case ‘/‘: syn=16;token[m++]=ch; break;
166         case ‘(‘: syn=27;token[m++]=ch; break;
167         case ‘)‘: syn=28;token[m++]=ch; break;
168         case ‘;‘: syn=26;token[m++]=ch; break; 
169         case ‘#‘: syn=0;token[m++]=ch; break;
170         case ‘:‘: syn=17;token[m++]=ch; break;
171         default: syn=-1;  break; 
172         }  
173     }  
174         token[m++]=‘\0‘;  
175 }