合肥工业大学HFUT编译原理课程设计---算数表达式转四元式语法制导翻译（C++实现 QT实现GUI）

本文主要是介绍合肥工业大学HFUT编译原理课程设计---算数表达式转四元式语法制导翻译（C++实现 QT实现GUI），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

部分代码如下(仅供参考）

//部分函数和数据结构设计省略，可通过最下方链接下载

void firstvt_lastvt()     //遍历一遍所有产生式，更新firstvt、lastvt集合
{for(int s = 0; s < grammar.size(); s++){string grammar_this = grammar[s];       //存储每一次遍历的产生式int t = grammar_this.find("->");        //t为‘-’的位置string grammar_left = grammar_this.substr(0, t);  //左串 即非终结符t+=2;string grammar_right = grammar_this.substr(t);     //右串vector<string> Y;Y = splitStringtoVector(grammar_right);         //右串分割为终结符与非终结符组成的vector一元组int k = Y.size();//Y[0]为终结符  P -> a...if(vt.count(Y[0]) != 0)firstvt[vn[grammar_left]].insert(Y[0]);//Y[1]为终结符  P -> Qa...else if(k > 1 && vt.count(Y[1]) != 0)firstvt[vn[grammar_left]].insert(Y[1]);//Y[0]为非终结符 P -> Q...if(vn.count(Y[0]) != 0){firstvt[vn[grammar_left]] = merge_set(firstvt[vn[grammar_left]],firstvt[vn[Y[0]]]);}// P -> ...aif(vt.count(Y[k-1]) != 0)lastvt[vn[grammar_left]].insert(Y[k-1]);// P -> ...aQelse if(k > 2 && vt.count(Y[k-2]) != 0)lastvt[vn[grammar_left]].insert(Y[k-2]);// P -> ...Qif(vn.count(Y[k-1]) != 0)lastvt[vn[grammar_left]] = merge_set(lastvt[vn[grammar_left]],lastvt[vn[Y[k-1]]]);}
}void iteration()    //迭代计算firstvt与lastvt集合
{bool flag = false; //收敛标志set <string> old_firstvt[50];set <string> old_lastvt[50];int times = 0;                   //直到收敛经历的迭代轮数while(!flag){flag = true;times++;firstvt_lastvt();for(auto t = vn.begin(); t != vn.end(); t++){if(firstvt[t->second].size() != old_firstvt[t->second].size() || lastvt[t->second].size() != old_lastvt[t->second].size())  //不收敛flag = false;old_firstvt[t->second] = firstvt[t->second];old_lastvt[t->second] = lastvt[t->second];}}cout << "times: " << times << endl;
}float string_to_float(string s)
{if(s[0] == '-')return -string_to_float(s.substr(1));float ans = 0;if(s.find('.') != string::npos){string l = s.substr(0,s.find('.'));string r = s.substr(s.find('.')+1);float base_l = 1;float base_r = 0.1;for(int i = l.size()-1; i >= 0; i--){ans+=(l[i] - '0')*base_l;// cout << ans << endl;base_l*=10;}for(int i = 0; i < r.size(); i++){ans+=(r[i] - '0')*base_r;base_r/=10;// cout << ans << endl;}}else{float base = 1;for(int i = s.size()-1; i >= 0; i--){ans+=(s[i] - '0')*base;base*=10;// cout << ans << endl;}}return ans;
}int get_ind(string s)   //获取中间结果下标
{int ans = 0;int base = 1;for(int i = s.size()-1; i > 0; i--){ans+=(s[i]-'0')*base;base*=10;}return ans;
}bool contain_alp(string s)  //输入表达式是否包含字母
{for(int i = 0; i < s.size(); i++){if(s[i] >= 'a' && s[i] <= 'z')return true;}return false;
}void main_control(string inText)
{vector <string>().swap(s);vector <string>().swap(sm);bool num_alp = contain_alp(inText); //true为含字母表达式FILE *history = fopen("C:\\Users\\21911\\Desktop\\history.txt","a+");if(history == nullptr){cout << "历史文件获取失败！\n";return;}FILE *f = fopen("C:\\Users\\21911\\Desktop\\curAnalysis.txt","w+");   //以重写方式打开文件if(f == nullptr){cout << "open file error!\n";return;}ind = 1;int timess = 0; //规约次数string in = inText;in_before = splitStringtoVector(in);for(int i = 0; i < in_before.size(); i++)cout << in_before[i] << " ";cout << endl;in = trans(in); //转换in_after = splitStringtoVector(in);in_after.insert(in_after.end(),1,"#");in_before.insert(in_before.end(),1,"#");int index = 0;  //指示in_afters.push_back("#");sm.push_back("#");  //结束符入栈int k = 0;  //指示符号栈栈顶int j;      //指示最靠顶部的终结符string a;   //指示下一输入符号string Q;   //存储可规约串中间的终结符string pp = "T0";float result[MAXN]; //存放中间结果 Tk 的值  Tk = result[k]string result_alp[MAXN];int indind = 0; //指示使用到的编号Tk的下标ktry{do{cout << timess++ << ": ";for(int u = 0; u < s.size(); u++)cout << s[u];cout << setw(15) << "\t";for(int u = 0; u < sm.size(); u++)cout << sm[u];cout << endl;a = in_after[index++];         //下一输入符号if(vt.count(s[k]) != 0)   //即in_[i] 属于 vtj = k;elsej = k-1;                //栈内最靠顶部的终结符while(table[vt[s[j]]][vt[a]] == 1)    //最靠近栈顶的终结符的优先级大于现行输入终结符  进行规约{do{Q = s[j];if(j>=1 && vt.count(s[j-1]) != 0)j=j-1;elsej=j-2;}while(table[vt[s[j]]][vt[Q]] == 0);   //找到可规约串的开头//规约s[j+1] ~ s[k]int ss = match(s,j+1,k);            //找到此步进行规约用到的产生式编号if(ss == -1){illegal = false;exit(1);}float op_l,op_r;                    //此步规约式的左右操作数string temp1,temp2,temp3;           //暂存左右操作数与操作符//s[j+1] s[j+2] s[j+3]if(ss == 1 || ss == 2 || ss == 4 || ss == 5)    //若为 + - * / 运算{temp1 = sm[j+1];    //左操作数 （为Tk编号 或者 字符串）temp2 = sm[j+2];    //操作符temp3 = sm[j+3];    //右操作数 （为Tk编号 或者 字符串）if(!num_alp)    //不含字母/**/{// str.append(tos(result[get_ind(temp1)]) + tos(result[get_ind(temp3)]) + temp2);if(temp1[0] == 'T')op_l = result[get_ind(temp1)];elseop_l = string_to_float(temp1);if(temp3[0] == 'T')op_r = result[get_ind(temp3)];elseop_r = string_to_float(temp3);//获取左右操作数的float形式// cout << op_l << "  " << op_r;switch(temp2[0])    //对 + - * /分类   获取结果存入result[indind]{case '+':result[indind] = op_l + op_r; break;case '-':result[indind] = op_l - op_r; break;case '*':result[indind] = op_l * op_r; break;case '/':result[indind] = op_l / op_r; break;}// cout << "  " << result[indind] << endl;string stream = "(" + sm[j+2] + ", " + sm[j+1] + ", "  + sm[j+3] + ", " +  pp + ")\t\t" + pp + "=";fputs(stream.data(),f);fprintf(f, "%0.6f\n",result[indind]);       //写入文件}else{result_alp[indind] = temp1+temp2+temp3;string stream = "(" + sm[j+2] + ", " + sm[j+1] + ", "  + sm[j+3] + ", " +  pp + ")\t\t" + pp + "=";fputs(stream.data(),f);/*fprintf(f, "%s\n",result_alp[indind]);*/fputs((result_alp[indind]+'\n').data(),f);//写入文件}}// s[j+1]else if(ss != 8)    // 非F->(E) 即不带()的产生式{if(!num_alp){if(sm[j+1][0] == 'T')op_l = result[get_ind(sm[j+1])];elseop_l = string_to_float(sm[j+1]);result[indind] = op_l;string stream = "( =: ," + sm[j+1] + ", " + pp + ")\t\t\t" + pp + "=";fputs(stream.data(),f);fprintf(f, "%0.6f\n",result[indind]);}else {result_alp[indind] = sm[j+1];string stream = "( =: ," + sm[j+1] + ", " + pp + ")\t\t\t" + pp + "=";fputs(stream.data(),f);
//                    fprintf(f, "%s\n",result_alp[indind]);fputs((result_alp[indind]+'\n').data(),f);}}// s[j+1]='(' s[j+2] s[j+3]=')'else    // F->(E)单独分析  E位于sm[j+2]的位置{if(!num_alp){if(sm[j+2][0] == 'T')op_l = result[get_ind(sm[j+2])];elseop_l = string_to_float(sm[j+2]);result[indind] = op_l;string stream = "( =: ," + sm[j+2] + ", " + pp + ")\t\t\t" + pp + "=";fputs(stream.data(),f);fprintf(f, "%0.6f\n",result[indind]);}else{result_alp[indind] = sm[j+2];string stream = "( =: ," + sm[j+2] + ", " + pp + ")\t\t\t" + pp + "=";fputs(stream.data(),f);fputs((result_alp[indind]+'\n').data(),f);}}// 删除s[j+1]~s[k]for(int q = j+1; q <= k; q++){s.erase(s.begin()+j+1);// if(ss != 7 && ss != 6 && ss != 3 && ss != 0)sm.erase(sm.begin()+j+1);}k = j+1;    //重置符号栈栈顶位置s.push_back(grammar[ss].substr(0,grammar[ss].find("->")));// 将找到的规约所用的产生式的左部加入符号栈pp = "T";pp.append(to_string(indind++));sm.push_back(pp);//新建一个中间值Tk加入带语义的符号栈pp = "T";pp.append(to_string(indind));   //下一个存放中间值中间编号cout << timess++ << ": ";for(int u = 0; u < s.size(); u++)cout << s[u];cout << setw(15) << "\t";for(int u = 0; u < sm.size(); u++)cout << sm[u];cout << endl;//输出规约后的符号栈}//退出循环 即table[vt[s[j]]][vt[a]] != 1if(table[vt[s[j]]][vt[a]] == -1 || table[vt[s[j]]][vt[a]] == 0){// cout << "1";k++;s.push_back(a);try{if(index >= 1)sm.push_back(in_before[index-1]);}catch(exception &e){cout << "002\n";cout << index;throw(e);}}if(table[vt[s[j]]][vt[a]] == -2)//算符优先分析表中为空cout << "error\n";}while(a != "#");}catch(exception &e){cout << "here\n";throw(e);}if(illegal){string his = inText+"\n";fputs(his.data(),history);if(indind >=1 && !num_alp)his = to_string(result[indind-1]);else if(indind >= 1 && num_alp)his = inText;his+='\n';fputs(his.data(),history);}fclose(history);fclose(f);in_before.clear();in_after.clear();pp.clear();f = nullptr;history = nullptr;
}