• 一、 实验目的
• 二、 实验内容
• 三、 实验要求
• 四、 运行结果
  • 1.解析文法
  • 2.语法分析

一、 实验目的

设计一个LL(1)语法分析器，利用语法分析器对符号串的识别，加深对语法分析原理的理解。

二、 实验内容

设计并实现一个LL(1)语法分析器，实现对算术文法G[E]:E->E+T|T T->TF|F F->(E)|i所定义的符号串进行识别，例如符号串(string1.txt) abc+age+80为文法所定义的句子，符号串(string2.txt) (abc-80(s5)不是文法所定义的句子。

三、 实验要求

• 检测左递归，如果有则进行消除，实现remove_left_recursion()函数；消除直接左递归（已实现）。

• 求解FIRST集和FOLLOW集，分别实现getFirst()和getFollow()函数；

• 理解构建LL(1)分析表getTable()中的代码，实现格式打印分析表的功能（显示Table部分）；

• 对于输入符号串，实现自顶向下的LL(1)分析，打印出分析过程：AnalyzePredict函数。

四、 运行结果

测试源文件：

E->T|E+T;

T->F|T*F;

F->i|(E);

1.解析文法

	原文法	消除左递归后
规格显示
FIRST集
FOLLOW集
Table表

2.语法分析

1)对string1 (string1.txt)的tocken(out1.txt)进行语法分析

String1.txt	out1.txt

分析结果parse_result1.txt

2)对string2 (string2.txt)的tocken(out2.txt)进行语法分析

String2.txt	Out2.txt

分析结果parse_result2.txt

实验代码:

parse_my.cpp

#include 
#include 
#include 
#include 
#include 

lex.cpp

#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
const int maxn = 1e4;
const int maxlen = 1e4;
char operate[11][10] = { "+","-","*","/",">","<","=","(",")",";" ,"|"};
char keyword[5][10] = { "if","then","else","while","do" };

class lexical {
private:
	static const int rowope = 11;//操作符个数	
	static const int rowkey = 5;//关键字个数
	struct Twotuples {
		char kind[10];
		char proper[10];
	}tuples[maxlen];
	string filename;
public:
	bool isCal(char *s, int &length) {
		char sub[100];
		for (int i = 0; i < rowope; i++) {
			int len = strlen(operate[i]);
			strncpy(sub, s, len);
			sub[len] = '\0';
			if (strcmp(sub, operate[i]) == 0) {
				length = len;
				return true;
			}
		}
		return false;
	}
	bool isKey(char *s, int &length) {
		char sub[100];
		int num = 0;
		while (isalpha(*(s + num))) {
			num++;
		}
		length = num;
		for (int i = 0; i < rowkey; i++) {
			strncpy(sub, s, length);
			sub[length] = '\0';
			if (strcmp(sub, keyword[i]) == 0 && !isalpha(*(s + length))) {
				return true;
			}
		}
		return false;
	}
	bool isTen(char *s, int &length) {
		if (s[0] == '0'&&!isdigit(s[1]) && s[1] != 'x') {
			length = 1;
			return true;
		}
		else
			if (s[0] >= '1'&&s[0] <= '9') {
				int num = 0;
				while (isdigit(*(s + num))) {
					num++;
				}
				length = num;
				return true;
			}
		return false;
	}
	bool isEight(char *s, int &length) {
		if (s[0] == '0' && (s[1] >= '1'&&s[1] <= '7')) {
			int num = 0;
			while (s[num] >= '0'&&s[num] <= '7') {
				num++;
				cout<<"1";
			}
			length = num;
			return true;
		}
		return false;
	}
	bool isSixteen(char *s, int &length) {
		if (s[0] == '0' && s[1] == 'x' && ((s[2] >= '0'&&s[2] <= '9') || (s[2] >= 'a'&&s[2] <= 'f'))) {
			int num = 2;
			while ((s[num] >= '0'&&s[num] <= '9') || (s[num] >= 'a'&&s[num] <= 'f')) {
				num++;
				cout<<"2";
			}
			length = num;
			return true;
		}
		return false;
	}
	void scan(char *str, int &p1, int &p2) {
		int len = 0;
		char str_[] = "-";
		char sub[100];
		//运算符和界符
		if (isCal(str + p1, len)) {

			strncpy(sub, str + p1, len);
			sub[len] = '\0';
			strcpy(tuples[p2].kind, sub);
			strcpy(tuples[p2].proper, str_);
			p1 += len;
			p2++;
		}
		//关键字
		if (isKey(str + p1, len)) {
			strncpy(sub, str + p1, len);
			sub[len] = '\0';

			strcpy(tuples[p2].kind, sub);
			strcpy(tuples[p2].proper, str_);
			p1 += len;
			p2++;
		}
		//标识符
		if (isalpha(*(str + p1))) {
			int len = 0;
			while (isalpha(*(str + p1 + len)) || isdigit(*(str + p1 + len))) {
				len++;
				cout<<"3";
			}
			strncpy(sub, str + p1, len);
			sub[len] = '\0';
			strcpy(tuples[p2].kind, "0");
			strcpy(tuples[p2].proper, sub);
			p1 += len;
			p2++;
		}
		//十进制数字

		if (isTen(str + p1, len)) {
			strncpy(sub, str + p1, len);
			sub[len] = '\0';

			strcpy(tuples[p2].kind, "1");
			strcpy(tuples[p2].proper, sub);
			p1 += len;
			p2++;
		}
		if (isEight(str + p1, len)) {
			strncpy(sub, str + p1 + 1, len - 1);
			sub[len - 1] = '\0';
			strcpy(tuples[p2].kind, "2");
			strcpy(tuples[p2].proper, sub);
			p1 += len;
			p2++;
		}
		if (isSixteen(str + p1, len)) {
			strncpy(sub, str + p1 + 2, len - 2);
			sub[len - 2] = '\0';

			strcpy(tuples[p2].kind, "3");
			strcpy(tuples[p2].proper, sub);
			p1 += len;
			p2++;
		}

	}
	lexical(string inputfile , string outputfile) {
		this->filename = inputfile;
		char *buffer = new char[maxlen];
		ifstream in(filename);
		if (!in.is_open()) {
			cout << "文件打开失败" << endl;
			exit(1);
		}
		in.getline(buffer, maxlen, '#');
		int len = strlen(buffer);
		bool flagend = false;
		for (int i = 0; i < strlen(buffer); i++) {
			if (buffer[i] == '#') {
				flagend = true;
				break;
			}
		}
		if (!flagend)buffer[len++] = '#';
		buffer[len] = '\0';
		cout << buffer << endl;
		int buf_ptr = 0;
		int tup_ptr = 0;


		while (true) {
			if (buffer[buf_ptr] == '#')break;
			if (buffer[buf_ptr] == ' ' || buffer[buf_ptr] == '\n') {
				buf_ptr++;
				continue;
			}
			if (buffer[buf_ptr] == '\t') {
				buf_ptr += 4;
				continue;
			}
			scan(buffer, buf_ptr, tup_ptr);
		}
		cout.setf(std::ios::left);
		ofstream out(outputfile);
		for (int i = 0; i < tup_ptr; i++) {
			out  << "<" << setw(5) << tuples[i].kind << "," << setw(5) << tuples[i].proper << ">" << endl;
			cout << "<" << setw(5) << tuples[i].kind << "," << setw(5) << tuples[i].proper << ">" << endl;
		}
		
		
	}
};
int main()
{
	string pwd = "C:\\Users\\46855\\Desktop\\c\\grammaticalAnalysis\\";
	// string filename1 = pwd + "parse_test1.txt";
	
	// string filename1 = pwd + "string1.txt";
	// string filename2= pwd + "Parsing\\out1.txt";

	string filename1 = pwd + "string2.txt";
	string filename2= pwd + "Parsing\\out2.txt";

	lexical *text = new lexical(filename1,filename2);
	system("pause");
	return 0;
}