0916作业二词法分析

  1 #include<stdio.h>
  2 #include<string.h>
  3 #include<stdlib.h>
  4 char prog[800],token[8];
  5 char ch;
  6 int syn,p,q,sum;
  7 char *rwtab[6]={"begin","if","then","while","do","end"};
  8 void scaner();
  9 main()
 10 {
 11     p=0;
 12     printf("
please input the source code:
");
 13     do{
 14         ch=getchar();
 15         prog[p]=ch;
 16         p++;
 17     }while(ch!='#');
 18     p=0;
 19     do
 20     {
 21         scaner();
 22         switch(syn)
 23         {
 24             case 11:printf("
(%d,%d)",syn,sum);break;
 25             case -1:printf("
(%s,出错)",token);break;
 26             default:printf("
(%d,%s)",syn,token);
 27         }
 28     }while(syn!=0);
 29 }
 30 
 31 
 32 void scaner()
 33 {
 34 
 35     int i;
 36     sum=0;
 37     for(q=0;q<8;q++)
 38         token[q]=NULL;
 39     ch=prog[p];
 40     q=0;
 41     while(ch==' '||ch=='
')
 42     {
 43         p++;
 44         ch=prog[p];    
 45     }
 46     if(('a'<=ch)&&(ch<='z')||('A'<=ch)&&(ch<='Z'))
 47     {
 48         while(('a'<=ch)&&(ch<='z')||('A'<=ch)&&(ch<='Z')||(ch>='0'&&ch<='9'))
 49         {
 50             token[q]=ch;
 51             p++;
 52             ch=prog[p];    
 53             
 54             q++;
 55         }
 56         syn=10;
 57         for(i=0;i<6;i++)
 58         {
 59              if(strcmp(token,rwtab[i])==0)
 60              {
 61                  syn=i+1;
 62                  break;
 63              }    
 64         }
 65     }
 66     else if(ch>='0'&&ch<='9')
 67     {
 68         while((ch>='0')&&(ch<='9'))
 69         {
 70             sum=sum*10+ch-'0';
 71             p++;
 72             ch=prog[p];
 73         }
 74         syn=11;
 75     }
 76     else switch(ch)
 77     {
 78         case '+':
 79              syn=13;
 80              token[q++]=ch;
 81              p++;
 82              break;
 83         case '-':
 84             syn=14;
 85              token[q++]=ch;
 86              p++;
 87              break;
 88         case '*':
 89             syn=15;
 90              token[q++]=ch;
 91              p++;
 92              break;
 93         case '/':
 94             syn=16;
 95              token[q++]=ch;
 96              p++;
 97              break;
 98         case ':':
 99             syn=17;
100              token[q++]=ch;
101              p++;
102              if(prog[p]=='=')
103              {
104                  syn=18;
105                  ch=prog[p];
106                  token[q++]=ch;
107                  p++;
108              }
109              break;
110         case '<':
111             syn=20;
112              token[q++]=ch;
113              p++;
114              if(prog[p]=='>')
115              {
116                  syn=21;
117                  ch=prog[p];
118                  token[q++]=ch;
119                  p++;
120              }
121              if(prog[p]=='=')
122              {
123                  syn=22;
124                  ch=prog[p];
125                  token[q++]=ch;
126                  p++;
127              }
128              break;
129         case '>':
130             syn=23;
131              token[q++]=ch;
132              p++;
133               if(prog[p]=='=')
134              {
135                  syn=24;
136                  ch=prog[p];
137                  token[q++]=ch;
138                  p++;
139              }
140              break;
141         case '=':
142             syn=25;
143              token[q++]=ch;
144              p++;
145              break;
146         case ';':
147             syn=26;
148              token[q++]=ch;
149              p++;
150              break;
151         case '(':
152             syn=27;
153              token[q++]=ch;
154              p++;
155              break;
156         case ')':
157             syn=28;
158              token[q++]=ch;
159              p++;
160              break;
161           case '#':
162              syn=0;
163              token[q++]=ch;
164              break;
165     }
166 }
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原文地址：https://www.cnblogs.com/zzy999/p/4826964.html