【编译原理】手工构造词法分析器

【问题描述】通过设计c语言常见单词的正规文法或正规式，而后得到NFA，再确定化得到DFA，根据DFA的转换矩阵或转换图，用c++语言实现词法分析器。
【输入形式】输入一段完整的c语言程序
【输出形式】各类单词的token字【样例输入】int main(){int a = 10;double b = -20.9;if(a<=b)        a+=b;return a;}【样例输出】line1:(type, int)line1:(keyword, main)line1:(bracket, ()line1:(bracket, ))line1:(bracket, {)line2:(type, int)line2:(identify, a)line2:(OPT, =)line2:(integer, 10)line2:(bracket, ;)line3:(type, double)line3:(identify, b)line3:(OPT, =)line3:(decimal, -20.9)line3:(bracket, ;)line4:(keyword, if)line4:(bracket, ()line4:(identify, a)line4:(OPT, <=)line4:(identify, b)line4:(bracket, ))line5:(identify, a)line5:(OPT, +=)line5:(identify, b)line5:(bracket, ;)line6:(keyword, else)line6:(identify, a)line6:(OPT, =)line6:(integer, 0)line6:(bracket, ;)line7:(keyword, return)line7:(identify, a)line7:(bracket, ;)line8:(bracket, })【样例说明】需要识别的关键字包括void, int, main, double, return, float, if, else, do, while, for, scanf, printf, char, sqrt, abs, 运算符(算术、关系、逻辑、位)；需要识别的其他单词有标识符, 整数（十进制形式、指数形式），实数（十进制形式、指数形式），字符串；过滤注释及空格。【评分标准】根据设计文档的质量、lex文件的正确性，代码的正确性、代码的时间空间复杂度、识别单词的种类等综合评分

构造DFA:

看起来也不是DFA

直接上代码：

#include <iostream>
#include <string.h>
#include <vector>using namespace std;vector<string> keyword = { "scanf","printf","if","else","for","while","return","do","main","abs","sqrt","float" };
vector<string> type = { "int","void","char","double","short" };
vector<char> bracket = { ',', '\\', ';', ':', '(', ')', '[',  ']', '{', '}', '"', '\'' };struct Store {int line = 0;string token;string word;
};vector<Store> msg;class Compile
{public:void scan();void print();void Pushmsg(string s);void JudgeFloat(string s);
private:int line = 1;char ch = ' ';string word;Store temp;
};
void Compile::Pushmsg(string s)
{temp.line = line;temp.token = s;temp.word = word;msg.push_back(temp);word.clear();
}
void Compile::JudgeFloat(string s)
{word += ch;ch = getchar();if (ch == '+' || ch == '-'){word += ch;ch = getchar();}if (ch < '1' || ch > '9'){cout << "Error at Line " << line << ": Illegal floating point number \"" << word << "\".\n";exit(-1);}else{word += ch;while ((ch = getchar()) && (ch >= '0' && ch <= '9')){word += ch;}Pushmsg("float");}
}
void Compile::scan()
{/*读取第一个有效字符*/ch = getchar();while (ch == ' ' || ch == '\n'){if (ch == '\n')line++;ch = getchar();}while (ch != '\0' && ch != EOF){while (ch == ' ' || ch == '\n'){if (ch == '\n')line++;ch = getchar();}//判断是否整数、小数、浮点数if (ch == '+' || ch == '-'){word += ch;ch = getchar();if (ch == '='){word += ch;Pushmsg("OPT");ch = getchar();}elseif (ch >= '1' && ch <= '9'){word += ch;while ((ch = getchar()) && (ch >= '0' && ch <= '9')){word += ch;}Pushmsg("integer");}}if (ch >= '1' && ch <= '9'){word += ch;ch = getchar();while (ch >= '0' && ch <= '9'){word += ch;ch = getchar();}//判度小数、浮点数if (ch == '.'){word += ch;ch = getchar();while (ch >= '0' && ch <= '9'){word += ch;ch = getchar();}if (ch == 'e'){JudgeFloat(word);}elsePushmsg("decimal");}elsePushmsg("integer");}int flag = 0;if (ch == '_' || isalpha(ch)){while (isalnum(ch)||ch == '_'){word += ch;ch = getchar();}for (vector<string>::iterator it = keyword.begin(); it != keyword.end(); it++){if (word == (*it)){Pushmsg("keyword");flag = 1;}}if (flag == 0){for (vector<string>::iterator it = type.begin(); it != type.end(); it++){if (word == (*it)){Pushmsg("type");flag = 1;}}if (flag == 0){Pushmsg("identify");}}}if (ch == '/'){char temp = getchar();if (temp == '/'){do {ch = getchar();} while (ch != '\n');}elseif (temp == '*'){do {ch = getchar();} while (ch != '/');ch = getchar();}else if (temp == '='){word += "/=";Pushmsg("OPT");ch = getchar();}else{word += '/';Pushmsg("OPT");ch = getchar();}}// 0 开头的情况if (ch == '0'){word += ch; ch = getchar();Pushmsg("integer");}//对typeidentify进行判断char temp;if (ch == '%' || ch == '&'){temp = getchar();if (isalnum(temp)){word += ch;word += temp;Pushmsg("typeidentify");ch = getchar();}}int flag2 = 0;//对bracket进行匹配for (vector<char>::iterator it = bracket.begin(); it != bracket.end(); it++){if (ch == (*it)){word += ch; ch = getchar();Pushmsg("bracket");break;flag2 = 1;}}//bracket没有匹配成功，对OPT进行判断if (flag2 == 0){switch (ch){case '*':case '=':case '<':case '>':case '!':temp = getchar();if (temp == '=') {word += ch;word += temp; ch = getchar();Pushmsg("OPT");break;}else {word += ch; ch = getchar();Pushmsg("OPT");break;}break;default:break;}}}}void Compile::print()
{for (vector<Store>::iterator it = msg.begin(); it != msg.end(); it++)cout << "line" << (*it).line << ":(" << (*it).token << ", " << (*it).word << ')' << endl;}
int main()
{Compile cp;cp.scan();cp.print();
}

【编译原理】手工构造词法分析器相关推荐

html解析器编译原理,编译原理实验报告词法分析器（内含源代码）.docx
编译原理实验报告词法分析器(内含源代码) 编译原理实验(一) --词法分析器实验描述运行环境:vc++2008 对某特定语言A ,构造其词法规则. 该语言的单词符号包括: 1该程序能识别的单词符号 ...
C++：编译原理实验之词法分析器
一.实验目的学会针对DFA转换图实现相应的高级语言源程序. 深刻领会状态转换图的含义,逐步理解有限自动机. 掌握手工生成词法分析器的方法,了解词法分析器的内部工作原理. 加强对C语言的掌握二.实验 ...
编译原理：简单词法分析器的设计与实现
一.实验目的: 设计.编制并调试一个简单的c语言词法分析程序,加深对词法分析原理的理解二.实验要求: 对单词的构词规则有明确的定义: 编写的分析程序能够正确识别源程序中的单词符号: 识别出的单词以( ...
编译原理子集构造法实现
输入说明第一行点数n 边数m 集合中字符数目k 第二行集合中的字符接下去m行每一行三个值起点终点经过的边上的字符输出: 构造好的边新构造节点包含的原先的点的集合 #include ...
【编译原理】构造产生如下语言的上下文无关文法各一个：
13.构造产生如下语言的上下文无关文法各一个: (1) (an bm c2m | n,m≥0 } S->AB A->ε|aA B->ε|bBcc (2) w c wR| w∈{a,b ...
【编译原理】构造DFA例题
1.构造一个DFA,它接受Σ = {0,1}上能被5整除的二进制数列出状态转换表: 状态添0 添1 0 0 1 1 2 3 2 4 0 3 1 2 4 3 4 绘制DFA: 2.画出一个最简的DF ...
编译原理——构造词法分析器（基于 Flex 构造和手工构造）
文章目录一.概述二.基于 Flex 构造词法分析器 2.1 需求描述 2.2 编译流程 2.3 Flex 代码三.手工构造词法分析器 3.1 需求描述 3.2 实现流程 3.3 C++ 代码四 ...
编译原理——词法分析器
采用java图形化界面编写了java语言的词法分析器,该分析器可识别所有java关键字.软件工程课程中编译原理实验. Keyword.jvav package org.kyc.test1;public ...
编译原理——词法分析器的设计
两种设计方案以及各自优缺点我们先学手工构造词法分析器手工构造关系运算符的手工构造: 上面这个图其实我有点疑惑,下面说一下,我自己的理解 C语言中的关系运算符,有<. <=. > ...

【编译原理】手工构造词法分析器

构造DFA:

直接上代码：

【编译原理】手工构造词法分析器相关推荐

最新文章

热门文章