printf("Error! Can't create file : key0.txt"); return; } fclose (floading); /*建立保留字表文件：key0.txt*/ if ((floading=fopen("key1.txt","w"))==NULL) { printf("Error! Can't create file : key1.txt"); return; } /*建立分隔符表文件：key1.txt*/
没找到：写入整数常量表文件
写入输出文件 5. 浮点类型判断函数 void intb_search(char *word)
接收数据
查表
找到：写入输出文件
没找到：写入整数常量表文件
写入输出文件
2
6. 字符串常量判断函数 void cc_search(char *word) 7. 字符常量判断函数 void c_search(char *word)
二、实验目的
1、理解词法分析在编译程序中的作用； 2、掌握词法分析程序的实现方法和技术； 3、加深对有穷自动机模型的理解。
三、主要函数
void load ( ) void char_search (char *word) void main ( ) void intb_search(char *word) void scan ( ) void c_search(char *word) void inta_search(char *word) void cc_search(char *word)
4
if ((floading=fopen("key2.txt","w"))==NULL) {
printf("Error! Can't create file : key2.txt"); return; } fclose(floading); /*建立运算符表文件：key2.txt*/ if ((floading=fopen("key3.txt","w"))==NULL) { printf("Error! Can't create file : key3.txt"); return; } fclose (floading); /*建立标识符表文件：key3.txt*/ if ((floading=fopen("c40.txt","w"))==NULL) { printf("Error! Can't create file : c40.txt"); return; } fclose (floading); /*建立整数类型常量表文件：c40.txt*/ if ((floading=fopen("c41.txt","w"))==NULL) { printf("Error! Can't create file : c41.txt"); return; } fclose (floading); /*建立浮点类型常量表文件：c41.txt*/ if ((floading=fopen("c42.txt","w"))==NULL) { printf("Error! Can't create file : c42.txt"); return; } fclose (floading); /*建立字符类型常量表文件：c42.txt*/ if ((floading=fopen("c43.txt","w"))==NULL) { printf("Error! Can't create file : c43.txt"); return; } fclose (floading); /*建立字符串类型常量表文件：c43.txt*/ if ((floading=fopen("defination.txt","w"))==NULL) { printf("Error! Can't create file : defination.txt"); return; }
int mm; for (mm=0;mm<=34;mm++) {
xx0[mm]=0; } for (mm=0;mm<=9;mm++) {
xx1[mm]=0; } for (mm=0;mm<=30;mm++) {
xx2[mm]=0; } FILE *floading; if ((floading=fopen("key0.txt","w"))==NULL) {
3
char
*key0[]={"
","auto","break","case","char","const","continue","default","do","double","else","enum","extern","float","for","goto","if",
"int","long","register","return","short","signed","sizeof","static","struct","switch","typedef","_Complex","_Imaginary","
同 4、5 函数图 8.主扫描函数 void scan ( )
函数开始
读入源文件中的一个单词
判断 宏定义 无效字符
忽略 忽略
字符串
调用保留字及标识符函数 void char_search 进行处理
字符常量
调用字符常量判断函数 void c_search 进行处理
字符串常量
调用字符串常量判断函数 void cc_search 进行处理
编译原理 C 语言词法分析器
一、实验题目
编制并调试 C 词法分析程序。 a.txt 源代码:
main() { int sum=0 ,it=1;/* Variable declaration*/ if (sum==1) it++; else it=it+2; }
设计其词法分析程序，能识别出所有的关键字、标识符、常数、运算符（包括复合运算符，如++）、界符；能过 滤掉源程序中的注释、空格、制表符、换行符；并且能够对一些词法规则的错误进行必要的处理，如：标识符只 能由字母、数字和下划线组成，且第一个字符必须为字母或下划线。实验要求:要给出所分析语言的词法说明， 相应的状态转换图，单词的种别编码方案，词法分析程序的主要算法思想等。
四、设计
1.主函数 void main ( )
绘制程序界面
调用初始化函数：void load ( ) 实现文件的建立
调用主扫描函数：void scan ( ) 实现文件的扫描
分析完成后指引用户查看相关文件，直到用户输入退出命令
1
函数结束
2. 初始化函数 void load ( ) 通过文件指针建立相关文件
union","unsigned","void","volatile","while"};
/*保留字表*/
char *key1[]={" ","(",")","[","]","{","}",",",";","'"};
/*分隔符表*/
char
*key2[]={"
","+","-","*","/","%","<",">","==",">=","<=","!=","!","&&","||","<<",">>","~","|","^","&","=","?:","->","++","--",".","+
整数常量
调用整数类型判断函数 void inta_search 进行处理
浮点数常量
调用浮点类型判断函数 void intb_search 进行处理
注释
写入注释文件
限制符
查运算符、分隔符表并写入输出文件
五、关键代码
#include <stdio.h> #include <string.h> #include <stdlib.h>
=","-=","*=","/="Байду номын сангаас;