词法分析器_无符号数状态图分析

  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstring>
  4 #include <cstdlib>
  5 #define _KEY_WORDEND "waiting for your expanding"
  6 using namespace std;
  7 typedef struct //词的结构，二元组形式（单词种别，单词自身的值）
  8 {
  9     int typenum; //单词种别
 10     char * word;
 11 }WORD;
 12 char input[255];
 13 char token[255] = "";
 14 int p_input; //指针
 15 int p_token;
 16 char ch;
 17 char * rwtab[] = { "begin","if","then","while","do","end","int","main",
 18                         "else","float","double","return","cout",_KEY_WORDEND };
 19  
 20 WORD * scanner();//扫描
 21  
 22 int main()
 23 {
 24     int over = 1;
 25     WORD* oneword = new WORD;
 26  
 27     //实现从文件读取代码段
 28     cout << "read something from data.txt" << endl;
 29     FILE *fp;
 30     if((fp=freopen("data.txt","r",stdin))==NULL)
 31         {
 32                 printf("Not found file!\n");
 33                 return 0;
 34         }
 35         else
 36         {
 37                 while ((scanf("%[^#]s", &input)) != EOF)
 38                 {
 39                         p_input = 0;
 40                         printf("your words:\n%s\n", input);
 41                         while (over < 1000 && over != -1)
 42                         {
 43                                 oneword = scanner();
 44                                 if (oneword->typenum < 1000)
 45                                 {
 46                                         if(oneword->typenum != 999)
 47                                                 cout << "<"<< oneword->word <<","<< oneword->typenum <<">"<< endl;
 48                                 }
 49                                 over = oneword->typenum;
 50                         }
 51                         scanf("%[^#]s", input);
 52                 }
 53         }
 54     return 0;
 55 }
 56 
 57 
 58 
 59 //回退一个字符
 60 void retract()
 61 {
 62     p_input--;
 63 }
 64 
 65 //从输入缓冲区读取一个字符到ch中
 66 char m_getch()
 67 {
 68     ch = input[p_input];
 69     p_input++;
 70     return ch;
 71 }
 72 
 73 //拼接单词
 74 void concat()
 75 {
 76     token[p_token] = ch;
 77     p_token++;
 78     token[p_token] = ‘\0‘;
 79 }
 80 
 81 //检索关键字表格
 82 int reserve()
 83 {
 84     int i = 0;
 85     while(strcmp(rwtab[i], _KEY_WORDEND))
 86     {
 87         if (!strcmp(rwtab[i], token))
 88             return i + 1;
 89         i++;
 90     }
 91     return 10;//如果不是关键字，则返回种别码10
 92 }
 93 
 94 int cm(){
 95     concat();
 96     m_getch();
 97 }
 98 
 99 //判断是否数字
100 int (digit())
101 {
102     if (ch >= ‘0‘&&ch <= ‘9‘)
103         return 1;
104     else
105         return 0;
106 }
107 
108 //匹配e字符 
109 int (E()){
110     if (ch == ‘e‘||ch == ‘E‘)
111         return 1;
112     else
113         return 0;
114 }
115 
116 //匹配+/-字符 
117 int (as()){
118     if(ch == ‘-‘||ch ==‘+‘)
119         return 1;
120     else
121         return 0;
122 }
123 
124 //匹配小数点 
125 int dot(){
126     if(ch == ‘.‘)
127         return 1;
128     else
129         return 0;
130 }
131 
132 void getbc()
133 {
134     while (ch == ‘ ‘ || ch == 10)
135     {
136         ch = input[p_input];
137         p_input++;
138     }
139 }
140 
141 
142 //1->4
143 //3->4
144 //后面的匹配是一样的，创建一个函数复用
145 
146 //4->R
147 WORD * s4(WORD * myword){
148     cm();
149     if (digit()){
150         cm();
151         if (digit()){
152             while((digit())) cm();
153             retract(); //回退一个字符
154             myword->typenum = reserve();//判断是否为关键字，返回种别码
155             myword->word = token;
156             return myword;
157         }
158         else{//other
159             retract(); //回退一个字符
160             myword->typenum = reserve();//判断是否为关键字，返回种别码
161             myword->word = token;
162             return myword;
163         }
164     }
165     else if (as()){
166         cm();
167         if (digit()){
168             cm();
169             while(1){
170                 if (digit()){
171                     cm();
172                 }else{//other
173                     retract(); //回退一个字符
174                     myword->typenum = reserve();//判断是否为关键字，返回种别码
175                     myword->word = token;
176                     return myword;
177                 }
178             }
179         }
180     }
181 }
182 
183 
184 
185 WORD * scanner(){
186     WORD * myword = new WORD;
187     myword->typenum = 10;  //初始值
188     myword->word = "";
189     p_token = 0;   //单词缓冲区指针
190     m_getch();
191     getbc();//去掉空白
192     
193     if (digit()){
194         cm();
195         while(1){//进行环循环匹配
196             if (digit()){
197                 cm();
198             }
199             else if (E()){
200                 return s4(myword);
201             }
202             else if (dot()){
203                 cm();
204                 if (digit()){
205                     cm();
206                     while(1){//进行环循环匹配
207                         if (digit()){
208                             cm();
209                         }
210                         if (E()){
211                             return s4(myword);
212                         }else{//other
213                             retract(); //回退一个字符
214                             myword->typenum = reserve();//判断是否为关键字，返回种别码
215                             myword->word = token;
216                             return myword;
217                         }
218                     }
219                 }
220             }else{//other
221                 retract(); //回退一个字符
222                 myword->typenum = reserve();//判断是否为关键字，返回种别码
223                 myword->word = token;
224                 return myword;
225             }
226         }
227     }
228 }