简单的词法分析小程序

Posted 2020-08-13 笑看风云动

 

实验：词法分析

一.实验目的：编写一个词法分析

    实验要求：输入：源程序字符串

                 输出：二元组（种别，单词本身）

二.词法分析程序设计

   词法规则：字母<a|b|c|...|z>

                 数字<0|1|2|...|9>

                整数常数：<数字>

                标识符：<变量〉

               关键字：<main|scanf|printf|...|const>

               运算符：<+|-|*|...|:=>

               界符   :<(|)|,|;|.>

   各单词对应的种别码

 

                

三：源代码展示

  1 #include<stdio.h>
  2 #include<malloc.h> 
  3 #include<stdlib.h>
  4 #include<ctype.h>
  5 typedef struct node
  6 {
  7     char ch;
  8     struct node *next;
  9 }QNode,*QueuePtr;
 10 
 11 typedef struct
 12 {
 13     QueuePtr front;
 14     QueuePtr rear;
 15 }LinkQueue;
 16 
 17 LinkQueue Q;
 18 QueuePtr p;        //定义一个指针变量 
 19 char *keyword[30]={"main","scanf","printf","void","int","float","double","char","long","short","signed",
 20                "struct","do","while","for","switch","case","break","continue","if","define","typedef","union",
 21                 "static","sizeof","return","extern","goto","auto","const"};
 22 char *operatornum[6]={"+","-","*","/","++","--"};  
 23 char *comparison[8]={"<","<=","=",">",">=","<>","==","!="};  
 24 char *interpunction[8]={",",";",":=",".","(",")","{","}"};  
 25 char *biaoshifu[6]={"%","$","^","&","_","#"};   //特殊标识符  
 26 char *zhushifu[3]={"//","/*","*/"};          //注释符  
 27 char *luoji[3]={"&&","||","!"};             //逻辑运算符  
 28 char *k="";
 29 
 30 void InitQueue()      //初始化一个带节点的空队列 
 31 {
 32     Q.front=Q.rear=(QueuePtr)malloc(sizeof(QNode));
 33     if(!Q.front)   
 34       exit(0);
 35     Q.front->next=NULL;
 36 }
 37 void Printf()
 38 {
 39     QueuePtr p;        //定义一个指针变量 
 40     p=Q.front;
 41     while(!(p==Q.rear))
 42     {
 43         p=p->next;
 44         printf("%c",p->ch);
 45     }
 46     printf("\\n");
 47 }
 48 void Creat()    //创建队列 
 49 {
 50     char ch;
 51     QueuePtr p;
 52     printf("请输入您要分析的字符串");
 53     ch=getchar();
 54     while(ch!=\'@\')
 55     {
 56         p=(QueuePtr)malloc(sizeof(QNode));
 57         p->ch=ch;
 58         p->next=NULL;
 59         Q.rear->next=p;
 60         Q.rear=p;
 61         ch=getchar();
 62     }
 63 }
 64 
 65 
 66 int search(char searchstr[],int wordtype)//符号匹配   
 67 {  
 68     int i;  
 69     switch (wordtype)  
 70     {  
 71         case 1:  
 72             for(i=0;i<30;i++)  
 73             {  
 74                 if(strcmp(keyword[i],searchstr)==0)  
 75                 return i;  
 76             }  
 77             break;  
 78         case 2:  
 79             for(i=0;i<=5;i++)  
 80             {  
 81                 if(strcmp(operatornum[i],searchstr)==0)  
 82                 return 30+i;  
 83             }  
 84          break;  
 85               
 86         case 3:   
 87             for(i=0;i<=7;i++)  
 88             {  
 89              if(strcmp(comparison[i],searchstr)==0)  
 90                 return 36+i;  
 91             }  
 92             break;  
 93      
 94         case 4:   
 95             for(i=0;i<=7;i++)  
 96             {  
 97                 if(strcmp(interpunction[i],searchstr)==0)  
 98                 return 44+i;  
 99             }  
100     
101             break;  
102         case 5:   
103             for(i=0;i<=5;i++)  
104             {  
105                 if(strcmp(biaoshifu[i],searchstr)==0)  
106                     return 52+i;  
107             }  
108             break;  
109         case 6:  
110              for(i=0;i<=2;i++)  
111              {  
112                 if(strcmp(zhushifu[i],searchstr)==0)  
113                     return 58+i;  
114             }  
115             break;  
116         case 7:   
117             for(i=0;i<=2;i++)  
118             {  
119                 if(strcmp(luoji[i],searchstr)==0)  
120                     return 61+i;  
121             }  
122         break;  
123     }  
124   
125     return -1;  
126 }  
127 void Analyze()
128 {
129     char str;
130     char letter[20];  
131     char num[20];  
132     char other[20];  
133     int i;
134     do      
135     {
136         Q.front=Q.front->next;        //获取单个字符 
137         str=Q.front->ch;
138         if (isalpha(str)!=0)        //如果是字符 
139         {
140             i=-1;
141            while (isalnum(str)!=0)  
142           {  
143             letter[++i]=str;  
144             Q.front=Q.front->next;
145             str=Q.front->ch;  
146           }  
147            letter[i+1]=\'\\0\';  
148            if (search(letter,1)!=-1)  
149           {  
150             printf("( %d,%s )\\n",search(letter,1),letter);  
151             
152           }  
153           else  
154           {  
155               printf("( %d,%s )\\n",64,letter);   
156            }  
157         }    
158         else  
159         {  
160             if (isdigit(str)!=0)  
161             {
162                 i=-1;
163                 while (isdigit(str)!=0)  
164                 {  
165                    num[++i]=str;  
166                    Q.front=Q.front->next;
167                    str=Q.front->ch; 
168                 }  
169                 if(isalpha(str)!=0)         //数字后面是字符   
170                 {  
171                     while(isspace(str)==0)  
172                    {  
173                      num[++i]=str; 
174                      Q.front=Q.front->next; 
175                      str=Q.front->ch; 
176                     }  
177                    num[i+1]=\'\\0\';  
178                    printf("错误！非法标识符：%s\\n",num);  
179                 
180                 }  
181                 num[i+1]=\'\\0\';  
182                 printf("( %d,%s )\\n",65,num);  
183             }
184             else  
185             {
186               i=-1;    
187               if (isspace(str)!=0)  
188               {  
189                  Q.front=Q.front->next;
190                  str=Q.front->ch;
191                  
192               }  
193               while ((isspace(str)==0)&&(isalnum(str)==0))  
194               {  
195                   Q.front=Q.front->next;
196                  str=Q.front->ch; 
197                  other[++i]=str;  
198                 
199                  
200                }  
201                   other[i+1]=\'\\0\';  
202               if (search(other,2)!=-1)  
203                   printf("( %d,%s )\\n",search(other,2),other);  
204               else if (search(other,3)!=-1)  
205                   printf("( %d,%s )\\n",search(other,3),other);  
206               else if (search(other,4)!=-1)  
207                   printf("( %d,%s )\\n",search(other,4),other);  
208               else if (search(other,5)!=-1)  
209                   printf("( %d,%s )\\n",search(other,5),other);  
210               else if (search(other,6)!=-1)  
211                   printf("（ %s,注释符号 ）\\n",other);  
212               else if (search(other,7)!=-1)  
213                   printf("( %d,%s )\\n",search(other,7),other);  
214               else   
215                   printf("错误！非法字符：%s\\n",other);  
216             }
217         }  
218     }while(Q.front!=Q.rear);  
219      printf("词法分析结束，谢谢使用！\\n"); 
220 }
221 
222 int main()
223 {
224     
225     InitQueue();    //创建空链队列 
226     Creat();        //创建队列 
227     Printf();       //输出队列 
228     Analyze();      //词法分析 
229     return 0;
230 }