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 printf("你好");
73 for(i=0;i<30;i++)
74 {
75 if(strcmp(keyword[i],searchstr)==0)
76 return i;
77 }
78 break;
79 case 2:
80 for(i=0;i<=5;i++)
81 {
82 if(strcmp(operatornum[i],searchstr)==0)
83 return 30+i;
84 }
85 break;
86
87 case 3:
88 for(i=0;i<=7;i++)
89 {
90 if(strcmp(comparison[i],searchstr)==0)
91 return 36+i;
92 }
93 break;
94
95 case 4:
96 for(i=0;i<=7;i++)
97 {
98 if(strcmp(interpunction[i],searchstr)==0)
99 return 44+i;
100 }
101
102 break;
103 case 5:
104 for(i=0;i<=5;i++)
105 {
106 if(strcmp(biaoshifu[i],searchstr)==0)
107 return 52+i;
108 }
109 break;
110 case 6:
111 for(i=0;i<=2;i++)
112 {
113 if(strcmp(zhushifu[i],searchstr)==0)
114 return 58+i;
115 }
116 break;
117 case 7:
118 for(i=0;i<=2;i++)
119 {
120 if(strcmp(luoji[i],searchstr)==0)
121 return 61+i;
122 }
123 break;
124 }
125
126 return 0;
127 }
128 void Analyze()
129 {
130 char str;
131 char letter[20];
132 char num[20];
133 char other[20];
134 int i;
135 p=Q.front;
136 while(p!=Q.rear)
137 {
138
139 p=p->next; //获取单个字符
140 str=p->ch;
141 if (isalpha(str)!=0) //如果是字符
142 {
143 i=-1;
144 while (isalnum(str)!=0)
145 {
146 letter[++i]=str;
147 str=p->next->ch;
148 }
149 letter[i+1]=‘\0‘;
150 if (search(letter,1))
151 {
152 printf("( %d,%s )",search(letter,1),letter);
153
154 }
155 else
156 {
157 printf("( %d,%s )\n",65,letter);
158 }
159 }
160 else
161 {
162 if (isdigit(str)!=0)
163 {
164 i=-1;
165 while (isdigit(str)!=0)
166 {
167 num[++i]=str;
168 str=p->next->ch;
169 }
170 if(isalpha(str)!=0) //数字后面是字符
171 {
172 while(isspace(str)==0)
173 {
174 num[++i]=str;
175 str=p->next->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 )",64,num);
183 }
184 else
185 {
186 i=-1;
187 if (isspace(str)!=0)
188 {
189 str=p->next->ch;
190
191 }
192 while ((isspace(str)==0)&&(isalnum(str)==0))
193 {
194 other[++i]=str;
195 str=p->next->ch;
196 }
197 other[i+1]=‘\0‘;
198 if (search(other,2))
199 printf("( %d,%s )\n",search(other,2),other);
200 else if (search(other,3))
201 printf("( %d,%s )\n",search(other,3),other);
202 else if (search(other,4))
203 printf("( %d,%s )\n",search(other,4),other);
204 else if (search(other,5))
205 printf("( %d,%s )\n",search(other,5),other);
206 else if (search(other,6))
207 printf("（ %s,注释符号 ）\n",other);
208 else if (search(other,7))
209 printf("( %d,%s )\n",search(other,7),other);
210 else
211 printf("错误！非法字符：%s\n",other);
212 }
213 }
214 };
215 printf("词法分析结束，谢谢使用！\n");
216 }
217
218 int main()
219 {
220
221 InitQueue(); //创建空链队列
222 Creat(); //创建队列
223 Printf(); //输出队列
224 Analyze(); //词法分析
225 return 0;
226 }
时间： 2024-08-08 09:32:07