编译原理（第三版） 语法分析器

语法分析器在词法分析器的基础上增加了递归下降分析程序，咱也不知道啥是递归下降程序，咱也不想问。
但是有程序框图和伪代码把程序跑通咱还是比较在行滴。为了便于理解，debug过程中的输出也保留了。

下面是完整代码。

  1 /*
  2     begin a:= 9; x:=2*3;b:=a+x end#
  3     x:= a+b*c end #
  4 */
  5 #include 
  6 #include 
  7 #include <string.h>
  8 #define _KEY_WORD_END "waiting for your expanding"
  9 typedef struct
 10 {
 11     int typenum;
 12     char *word;
 13 }WORD;
 14 char input[255];
 15 char token[255]="";
 16 int p_input;
 17 int p_token;
 18 char ch;
 19 char* rwtab[] = {"begin","if","then","while","do","end",_KEY_WORD_END};
 20 WORD * scaner();
 21 WORD* oneword = new WORD;
 22 int syn,kk;
 23 void expression();
 24 void factor()
 25 {
 26     if(syn == 10 || syn == 11)
 27     {
 28         oneword = scaner();
 29         syn = oneword->typenum;
 30         printf("%s   %d\n",oneword->word,syn);
 31     }
 32     else if(syn == 27)
 33     {
 34         oneword = scaner();
 35         syn = oneword->typenum;
 36         printf("%s   %d\n",oneword->word,syn);
 37         expression();
 38         if(syn == 28)
 39         {
 40             oneword = scaner();
 41             syn = oneword->typenum;
 42             printf("%s   %d\n",oneword->word,syn);
 43         }
 44         else{
 45             printf("右括号错误\n");
 46             kk = 1;
 47         }
 48     }
 49     else
 50     {
 51         printf("表达式错误\n");
 52         kk = 1;
 53     }
 54     return;
 55 }
 56 void term()
 57 {
 58     factor();
 59     while(syn == 15 || syn == 16)
 60     {
 61         oneword = scaner();
 62         syn = oneword->typenum;
 63         printf("%s   %d\n",oneword->word,syn);
 64         factor();
 65     }
 66     return;
 67 }
 68 void expression()
 69 {
 70     term();
 71     while(syn == 13 || syn == 14)
 72     {
 73         oneword = scaner();
 74         syn = oneword->typenum;
 75         printf("%s   %d\n",oneword->word,syn);
 76         term();
 77     }
 78     return;
 79 }
 80 void statement()
 81 {
 82     if(syn == 10)
 83     {
 84         oneword = scaner();
 85         syn = oneword->typenum;
 86         printf("%s   %d\n",oneword->word,syn);
 87         if(syn == 18)
 88         {
 89             oneword = scaner();
 90             syn = oneword->typenum;
 91             printf("%s   %d\n",oneword->word,syn);
 92             expression();
 93         }
 94         else{
 95             printf("赋值号错误\n");
 96             kk = 1;
 97         }
 98     }
 99     else{
100         printf("语句错误\n");
101         kk = 1;
102     }
103     return;
104 }
105 void yucu()
106 {
107     statement();
108     while(syn == 26)
109     {
110         oneword = scaner();
111         syn = oneword->typenum;
112         printf("%s   %d\n",oneword->word,syn);
113         statement();
114     }
115     return;
116 }
117 void Irparser()
118 {
119     if(syn == 1)
120     {
121         oneword = scaner();
122         syn = oneword->typenum;
123         printf("%s   %d\n",oneword->word,syn);
124         yucu();
125 
126         if(syn==6)
127         {
128             oneword = scaner();
129             syn = oneword->typenum;
130             if(syn == 0 && (kk == 0))
131                 printf("success\n");
132         }
133         else{
134             if(kk != 1)
135             {
136                 printf("缺少end错误\n");
137                 kk = 1;
138             }
139         }
140     }
141     else{
142         printf("begin错误\n");
143         kk = 1;
144     }
145     return;
146 }
147 int main()
148 {
149     int over = 1;
150 
151     printf("Enter Your words(end with #):");
152     scanf("%[^#]s",input);
153     p_input = 0;
154     printf("Your words:\n%s\n",input);
155 
156         //获取下一个单词符号
157         oneword = scaner();
158         syn = oneword->typenum;
159         Irparser();
160 
161     printf("\npress # to exit:");
162     scanf("%[^#]s",input);
163     return 0;
164 }
165 char m_getch()
166 {
167     ch = input[p_input];
168     p_input = p_input+1;
169     return(ch);
170 }
171 void getbc()
172 {
173     while(ch == ' '||ch == 10)
174     {
175         ch = input[p_input];
176         p_input++;
177     }
178 }
179 void concat()
180 {
181     token[p_token] = ch;
182     p_token++;
183     token[p_token] = '\0';
184 }
185 int letter()
186 {
187     if((ch >= 'a'&& ch <= 'z')|| (ch >='A'&&ch <= 'Z'))
188         return 1;
189     else
190         return 0;
191 }
192 int digit()
193 {
194     if(ch >= '0'&&ch <='9')return 1;
195     else return 0;
196 }
197 int reserve()
198 {
199     int i = 0;
200     while(strcmp(rwtab[i],_KEY_WORD_END))
201     {
202         if(!strcmp(rwtab[i],token))
203             return i+1;
204         i++;
205     }
206     return 10;
207 }
208 void retract()
209 {
210     p_input--;
211 }
212 
213 char* dtb()
214 {
215     return NULL;
216 }
217 
218 WORD* scaner()
219 {
220 
221     WORD* myword = new WORD;
222     myword->typenum = 10;
223     myword->word = "";
224     p_token = 0;
225     m_getch();
226     getbc();
227     if(letter())
228     {
229         while(letter()||digit())
230         {
231             concat();
232             m_getch();
233         }
234         retract();
235         myword->typenum = reserve();
236         myword->word = token;
237         return(myword);
238     }
239     else if(digit())
240     {
241         while(digit())
242         {
243             concat();
244             m_getch();
245         }
246         retract();
247         myword->typenum = 11;
248         myword->word = token;
249         return(myword);
250     }
251     else switch(ch)
252     {
253         case'=':m_getch();
254             if(ch == '=')
255             {
256                 myword->typenum = 25;
257                 myword->word = "==";
258                 return(myword);
259             }
260             retract();
261             myword->typenum = 21;
262             myword->word = "=";
263             return(myword);
264             break;
265         case'+':
266             myword->typenum = 13;
267             myword->word = "+";
268             return(myword);
269             break;
270         case'-':
271             myword->typenum = 14;
272             myword->word = "-";
273             return(myword);
274             break;
275         case'*':
276             myword->typenum = 15;
277             myword->word = "*";
278             return(myword);
279             break;
280         case'/':
281             myword->typenum = 16;
282             myword->word = "/";
283             return(myword);
284             break;
285         case'(':
286             myword->typenum = 27;
287             myword->word = "(";
288             return(myword);
289             break;
290         case')':
291             myword->typenum = 28;
292             myword->word = ")";
293             return(myword);
294             break;
295         case'[':
296             myword->typenum = 28;
297             myword->word = "[";
298             return(myword);
299             break;
300         case']':
301             myword->typenum = 29;
302             myword->word = "]";
303             return(myword);
304             break;
305         case'{':
306             myword->typenum = 30;
307             myword->word = "{";
308             return(myword);
309             break;
310         case'}':
311             myword->typenum = 31;
312             myword->word = "}";
313             return(myword);
314             break;
315         case',':
316             myword->typenum = 32;
317             myword->word = ",";
318             return(myword);
319             break;
320         case':':m_getch();
321             if(ch == '=')
322             {
323                 myword->typenum = 18;
324                 myword->word = ":=";
325                 return(myword);
326             }
327             retract();
328             myword->typenum = 17;
329             myword->word = ":";
330             return(myword);
331             break;
332         case';':
333             myword->typenum = 26;
334             myword->word = ";";
335             return(myword);
336             break;
337         case'>':m_getch();
338             if(ch == '=')
339             {
340                 myword->typenum = 24;
341                 myword->word = ">=";
342                 return(myword);
343             }
344             retract();
345             myword->typenum = 23;
346             myword->word = ">";
347             return(myword);
348             break;
349         case'<':m_getch();
350             if(ch == '=')
351             {
352                 myword->typenum = 22;
353                 myword->word = "<=";
354                 return(myword);
355             }
356             else if(ch == '>')
357             {
358                 myword->typenum = 21;
359                 myword->word = "<>";
360                 return(myword);
361             }
362             retract();
363             myword->typenum = 20;
364             myword->word = "<";
365             return(myword);
366             break;
367         case'!':m_getch();
368             if(ch == '=')
369             {
370                 myword->typenum = 40;
371                 myword->word = "!=";
372                 return(myword);
373             }
374             retract();
375             myword->typenum = -1;
376             myword->word = "ERROR";
377             return(myword);
378             break;
379         case'#':
380             myword->typenum = 0;
381             myword->word = "#";
382             return(myword);
383             break;
384         case'\0':
385             myword->typenum = 0;
386             myword->word = "OVER";
387             return(myword);
388             break;
389         default: myword->typenum = -1;
390             myword->word = "ERROR";
391             return(myword);
392     }
393 }

 

 

转载于:https://www.cnblogs.com/--lr/p/10838712.html