521 lines
12 KiB
C++
521 lines
12 KiB
C++
#include <deque>
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#include <cstring>
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#include <fstream>
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#include <iostream>
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#include <sstream>
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#include <algorithm>
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#include <set>
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#include "grammar.h"
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Grammar::Grammar()
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{
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}
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Grammar::~Grammar()
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{
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}
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void Grammar::read_grammar() {
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ifstream infile;
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infile.open(grammar_file, ios::in);
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if (!infile.is_open())
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{
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cout << "读取文件失败" << endl;
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return;
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}
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string buf;
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string arrow = "->";
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string farrow;
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bool start_flag = true;
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string left;
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string forms;
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while (!infile.eof()) {
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// 清理 string
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buf.clear();
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left.clear();
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forms.clear();
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farrow.clear();
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grammar_rules.push_back(pair<string, vector<string>>());
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getline(infile, buf);
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stringstream ss(buf);
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// 读取产生式左侧
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ss >> left;
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grammar_rules.back().first = left;
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symbols.push_back(left);
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VNs.push_back(left);
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// 存储 start
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if (start_flag) {
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start = left;
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start_flag = false;
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}
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// 读取 -> 符号 并保证合法
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ss >> farrow;
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if (farrow != arrow) {
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cout << "语法读取出错" << endl;
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}
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// 读取产生式右侧
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while (ss >> forms)
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{
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grammar_rules.back().second.push_back(forms);
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symbols.push_back(forms);
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forms.clear();
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}
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}
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// 符号集 和 非终结符 去重
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set<string> ssymbols(symbols.begin(), symbols.end());
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symbols.clear();
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symbols.resize(ssymbols.size());
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symbols.assign(ssymbols.begin(), ssymbols.end());
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set<string> sVNs(VNs.begin(), VNs.end());
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VNs.clear();
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VNs.resize(sVNs.size());
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VNs.assign(sVNs.begin(), sVNs.end());
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// 符号集 和 非终结符 排序 以保证差集的成功
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sort(symbols.begin(), symbols.end());
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sort(VNs.begin(), VNs.end());
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// 取差集 得到终极符
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set_difference(symbols.begin(), symbols.end(), VNs.begin(), VNs.end(), back_inserter(VTs));
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infile.close();
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}
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void Grammar::print_grammar()
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{
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cout << "[start]: " << endl << start << endl << endl;
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cout << "[VTs]:" << endl;
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for (int i = 0; i < VTs.size(); i++) {
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cout << VTs[i] << " ";
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if (((i + 1) % 5) == 0)
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cout << endl;
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}
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cout << endl << endl;
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cout << "[VNs]:" << endl;
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for (int i = 0; i < VNs.size(); i++) {
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cout << VNs[i] << " ";
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if (((i + 1) % 5) == 0)
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cout << endl;
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}
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cout << endl << endl;
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cout << "[symbols]:" << endl;
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for (int i = 0; i < symbols.size(); i++) {
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cout << symbols[i] << " ";
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if (((i + 1) % 5) == 0)
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cout << endl;
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}
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cout << endl << endl;
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cout << "[grammar_rules]: " << grammar_rules.size() << endl;
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for (int i = 0; i < grammar_rules.size(); ++i) {
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cout << grammar_rules[i].first << " -> ";
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for (int j = 0; j < grammar_rules[i].second.size(); ++j) {
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cout << "\"" << grammar_rules[i].second[j] << "\" ";
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}
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cout << endl;
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}
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cout << endl << endl;
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}
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void Grammar::expand_grammar()
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{
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string new_start = start + "\'";
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pair<string, vector<string>> new_rule = pair<string, vector<string>>(new_start, vector<string>());
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new_rule.second.push_back(start);
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VNs.push_back(new_start);
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symbols.push_back(new_start);
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grammar_rules.insert(grammar_rules.begin(), new_rule);
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start = new_start;
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// 符号集排序
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sort(symbols.begin(), symbols.end());
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}
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void Grammar::init_grammar_set()
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{
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string symbol;
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// 对符号集中各符号进行推导 是否可以到达 $ 空符号
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for (int i = 0; i < symbols.size(); i++) {
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symbol = symbols[i];
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this->symbol_infer_empty(symbol);
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symbol.clear();
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}
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// 初始化符号在产生式的 出现 依赖 情况
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init_appears_depend();
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// 对符号集中各符号进行推导 FIRST 集
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for (int i = 0; i < symbols.size(); i++) {
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symbol = symbols[i];
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this->symbol_infer_first(symbol);
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symbol.clear();
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}
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// 对符号集中各符号进行推导 FOLLOW 集
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// 符号队列
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deque<string> queue;
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// 初次遍历所有符号 生成初始的 FOLLOW 集
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// 构建 start 的 FOLLOW 集
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follow[start] = this->symbol_infer_follow(start);
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follow[start].push_back("$");
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queue.push_back(start);
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// 构建除 start 的 FOLLOW 集
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for (int i = 0; i < symbols.size(); i++) {
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symbol = symbols[i];
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if (symbol == start) {
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symbol.clear();
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continue;
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}
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follow[symbol] = this->symbol_infer_follow(symbol);
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queue.push_back(symbol);
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symbol.clear();
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}
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// 对 符号队列 进行进一步生成
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while (!queue.empty()) {
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// 读取 符号队列 开头
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symbol = queue.front();
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queue.pop_front();
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// 若 FOLLOW 集发生改变
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vector<string> new_symbol_follow = this->symbol_infer_follow(symbol);
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if (follow[symbol].size() < new_symbol_follow.size()) {
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// 对依赖 该符号 的所有符号添加至 符号队列
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vector<string> dep = depend[symbol];
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for (int i = 0; i < dep.size(); i++) {
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queue.push_back(dep[i]);
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}
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follow[symbol] = new_symbol_follow;
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}
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symbol.clear();
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}
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}
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void Grammar::print_grammar_set()
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{
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// 打印符号在产生式的出现情况
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cout << "[left_appears]:" << endl;
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for (int i = 0; i < symbols.size(); i++) {
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cout << "LEFT( " << symbols[i] << " ) = {";
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for (int j = 0; j < left_appears[symbols[i]].size(); j++) {
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cout << " " << left_appears[symbols[i]][j] << " ";
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}
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cout << "}" << endl;
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}
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cout << endl << endl;
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cout << "[right_appears]:" << endl;
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for (int i = 0; i < symbols.size(); i++) {
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cout << "RIGHT( " << symbols[i] << " ) = {";
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for (int j = 0; j < right_appears[symbols[i]].size(); j++) {
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cout << " " << right_appears[symbols[i]][j] << " ";
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}
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cout << "}" << endl;
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}
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cout << endl << endl;
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// 打印 FOLLOW 集的依赖关系
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cout << "[depend]:" << endl;
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for (int i = 0; i < symbols.size(); i++) {
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cout << "DEPEND( " << symbols[i] << " ) = {";
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for (int j = 0; j < depend[symbols[i]].size(); j++) {
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cout << " " << depend[symbols[i]][j] << " ";
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}
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cout << "}" << endl;
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}
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cout << endl << endl;
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// 打印是否可以推导出 $ 空符号
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cout << "[infer_empty]:" << endl;
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for (int i = 0; i < symbols.size(); i++) {
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cout << symbols[i]<<" -> " << infer_empty[symbols[i]] << endl;
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}
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cout << endl << endl;
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// 打印 FIRST 集
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cout << "[FIRST]:" << endl;
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for (int i = 0; i < symbols.size(); i++) {
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cout << "FIRST( " << symbols[i] << " ) = {";
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for (int j = 0; j < first[symbols[i]].size(); j++) {
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cout << " " << first[symbols[i]][j] << " ";
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}
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cout << "}" << endl;
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}
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cout << endl << endl;
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// 打印 FOLLOW 集
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cout << "[FOLLOW]:" << endl;
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for (int i = 0; i < symbols.size(); i++) {
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cout << "FOLLOW( " << symbols[i] << " ) = {";
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for (int j = 0; j < follow[symbols[i]].size(); j++) {
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cout << " " << follow[symbols[i]][j] << " ";
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}
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cout << "}" << endl;
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}
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cout << endl << endl;
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}
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void Grammar::get_token_strings(vector<string>& my_token_strings)
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{
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token_strings.resize(my_token_strings.size());
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token_strings.assign(my_token_strings.begin(), my_token_strings.end());
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}
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void Grammar::print_token_strings()
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{
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for (int i = 0; i < token_strings.size(); i++) {
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cout << token_strings[i] << endl;
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}
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}
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void Grammar::init_appears_depend()
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{
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for (int k = 0; k < symbols.size(); k++) {
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left_appears[symbols[k]] = vector<int>();
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right_appears[symbols[k]] = vector<int>();
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depend[symbols[k]] = vector<string>();
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for (int i = 0; i < grammar_rules.size(); i++) {
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if (grammar_rules[i].first == symbols[k]) {
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// 产生式左侧相等 存入 left
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left_appears[symbols[k]].push_back(i);
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// 对该产生式构建依赖关系
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for (int m = 0; m < grammar_rules[i].second.size(); m++) {
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int n;
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// 判断该产生式右侧符号是否可以推导至 $ 空符号
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for (n = m + 1; n < grammar_rules[i].second.size(); n++) {
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if (!infer_empty[grammar_rules[i].second[n]]) {
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break;
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}
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}
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// 若可以推导 按照入栈的方式依次加入
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if (n == grammar_rules[i].second.size()) {
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if (symbols[k] != grammar_rules[i].second[m]) {
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depend[symbols[k]].push_back(grammar_rules[i].second[m]);
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}
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}
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}
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}
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for (int j = 0; j < grammar_rules[i].second.size(); j++) {
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// 产生式右侧相等 存入 left
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if (grammar_rules[i].second[j] == symbols[k]) {
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right_appears[symbols[k]].push_back(i);
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break;
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}
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}
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}
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}
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}
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bool Grammar::symbol_infer_empty(const string& symbol) {
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// 已经进行推导过
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if (infer_empty.find(symbol) != infer_empty.end()) {
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return infer_empty[symbol];
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}
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// 当符号为终结符时，当且仅当为 $ 可以推导出 $
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if (find(VTs.begin(), VTs.end(), symbol) != VTs.end()) {
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infer_empty[symbol] = (symbol == "$") ;
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return infer_empty[symbol];
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}
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// 当符号为非终结符时，通过产生式进行推导
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for (int i = 0; i < grammar_rules.size(); i++) {
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// 当该符号为产生式左侧时
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if (grammar_rules[i].first == symbol) {
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int j;
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vector<string> rule_right = grammar_rules[i].second;
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for (j = 0; j < rule_right.size(); j++) {
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// 递归推导 产生式右侧无法推导至 $ 时
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if (!(this->symbol_infer_empty(rule_right[j]))) {
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break;
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}
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}
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// 当且仅当产生式右侧可以推导至 $ 时
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if (j == rule_right.size()) {
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infer_empty[symbol] = true;
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return infer_empty[symbol];
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}
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}
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}
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// 当各产生式都无法推导至 $ 时，则无法推导
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infer_empty[symbol] = false;
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return infer_empty[symbol];
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}
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vector<string> Grammar::symbol_infer_first(const string& symbol)
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{
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// 已经推导过 FIRST 集
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if (first.find(symbol) != first.end()) {
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return first[symbol];
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}
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vector<string> symbol_first;
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// 当符号为终结符时 FIRST 集为它本身
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if (find(VTs.begin(), VTs.end(), symbol) != VTs.end()) {
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symbol_first.push_back(symbol);
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first[symbol] = symbol_first;
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return first[symbol];
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}
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// 当符号为非终结符时，通过产生式进行推导
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for (int i = 0; i < grammar_rules.size(); i++) {
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// 当该符号为产生式左侧时
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if (grammar_rules[i].first == symbol) {
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int j;
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for (j = 0; j < grammar_rules[i].second.size(); j++) {
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// 依次添加所有产生式右侧的
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vector<string> firsts = symbol_infer_first(grammar_rules[i].second[j]);
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for (int k = 0; k < firsts.size(); k++) {
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symbol_first.push_back(firsts[k]);
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}
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// 若产生式右侧无法推导至 $ 空字符时 中断
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if (!infer_empty[grammar_rules[i].second[j]]) {
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break;
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}
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}
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// 当且仅当产生式右侧可以推导至 $ 时 将 $ 加入到 FIRST 集中
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if (j == grammar_rules[i].second.size()) {
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symbol_first.push_back("$");
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}
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}
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}
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// 对当前 FIRST 集进行 去重 与 排序
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set<string> ssymbol_first(symbol_first.begin(), symbol_first.end());
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symbol_first.clear();
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symbol_first.resize(ssymbol_first.size());
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symbol_first.assign(ssymbol_first.begin(), ssymbol_first.end());
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sort(symbol_first.begin(), symbol_first.end());
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// 返回非终结符的 FIRST 集
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first[symbol] = symbol_first;
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return first[symbol];
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}
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vector<string> Grammar::symbol_infer_follow(const string& symbol)
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{
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vector<string> symbol_follow;
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// 获取该符号出现在哪些产生式右侧
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vector<int> right_appear = right_appears[symbol];
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for (int i = 0; i < right_appear.size(); i++) {
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int cnt;
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// 获取该产生式右侧的符号
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vector<string> rule_right = grammar_rules[right_appear[i]].second;
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// 依次遍历 该产生式右侧 至 该符号 后一位
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for (cnt = 0; cnt < rule_right.size(); cnt++) {
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if (rule_right[cnt] == symbol) {
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break;
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}
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}
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cnt++;
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// 遍历 剩余产生式右侧
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for (; cnt < rule_right.size(); cnt++) {
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// 依次获取 后置元素 的 FIRST 集
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vector<string> symbol_first = first[rule_right[cnt]];
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// 将 该 FIRST 集 循环添加至 symbol_follow 中
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for (int j = 0; j < symbol_first.size(); j++) {
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symbol_follow.push_back(symbol_first[j]);
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}
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// 若不可达 $ 中断遍历
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if (!infer_empty[rule_right[cnt]]) {
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break;
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}
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}
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// 当剩余产生式右侧均可到达 $ 时
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if (cnt == rule_right.size()) {
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if (follow.find(grammar_rules[right_appear[i]].first) != follow.end()) {
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// 将产生式左侧的 FOLLOW 集 加入到 当前符号的 FOLLOW 集中
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vector<string> first_follow = follow[grammar_rules[right_appear[i]].first];
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for (int j = 0; j < first_follow.size(); j++) {
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symbol_follow.push_back(first_follow[j]);
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}
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}
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}
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}
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// 删除不需要的 $ 空字符
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auto it = remove(symbol_follow.begin(), symbol_follow.end(), "$");
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auto it1 = symbol_follow.erase(it, symbol_follow.end());
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// 对当前 FOLLOW 集 进行去重排序
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set<string> ssymbol_follow(symbol_follow.begin(), symbol_follow.end());
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symbol_follow.clear();
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symbol_follow.resize(ssymbol_follow.size());
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symbol_follow.assign(ssymbol_follow.begin(), ssymbol_follow.end());
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sort(symbol_follow.begin(), symbol_follow.end());
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return symbol_follow;
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}
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