要求：
1．以S属性的语法制导定义为基础，将下表的语义规则嵌套在语法分析的过程中，即实现语法制导的翻译过程。
| 产 生 式 |
语 义 规 则 |
| L -> E n |
print (E.val) |
| E-> E1 + T |
E.val := E1 .val + T.val |
| E ->T |
E.val := T.val |
| T-> T1 * F |
T.val := T1.val * F.val |
| T ->F |
T.val := F.val |
| F->(E) |
F.val := E.val |
| F ->digit |
F.val := digit.lexval |
2．以词法分析和语法分析部分的上机结果为基础，添加语义分析部分。即以LR文法为基础。当进行产生式归约时执行对应的语义动作。
3．输入：
5+3+8*2
输出：24
注：只能完成加法和乘法的运算，相对于之前上传的LR文法只是添加了把数字变成符号的过程（即把(2+5)*5变成(a+a)*a）再定义一个数字栈，与符号栈的动作对应，最后取出数据栈栈顶就是结果
#include <iostream>
#include <string.h>
#include<stack>
using namespace std;
/*
E->E+T
E->T
T->T*F
T->F
F->(E)
F->id
*/
/*初始化分析表*/
void Initial(string analysis[12][9]){
/*移进规约*/
analysis[0][0] = "s5"; analysis[0][3] = "s4"; analysis[0][6] = "1"; analysis[0][7] = "2"; analysis[0][8] = "3";
analysis[1][1] = "s6"; analysis[1][5] = "acc";
analysis[2][1] = "r2"; analysis[2][2] = "s7"; analysis[2][4] = "r2"; analysis[2][5] = "r2";
analysis[3][1] = "r4"; analysis[3][2] = "r4"; analysis[3][4] = "r4"; analysis[3][5] = "r4";
analysis[4][0] = "s5"; analysis[4][3] = "s4"; analysis[4][6] = "8"; analysis[4][7] = "2"; analysis[4][8] = "3";
analysis[5][1] = "r6"; analysis[5][2] = "r6"; analysis[5][4] = "r6"; analysis[5][5] = "r6";
analysis[6][0] = "s5"; analysis[6][3] = "s4"; analysis[6][7] = "9"; analysis[6][8] = "3";
analysis[7][0] = "s5"; analysis[7][3] = "s4"; analysis[7][8] = "10";
analysis[8][1] = "s6"; analysis[8][4] = "ss";//表示s11
analysis[9][1] = "r1"; analysis[9][2] = "s7"; analysis[9][4] = "r1"; analysis[9][5] = "r1";
analysis[10][1] = "r3"; analysis[10][2] = "r3"; analysis[10][4] = "r3"; analysis[10][5] = "r3";
analysis[11][1] = "r5"; analysis[11][2] = "r5"; analysis[11][4] = "r5"; analysis[11][5] = "r5";
/*出现错误*/
analysis[0][1] = analysis[0][2] = analysis[0][5] = analysis[4][1] = analysis[4][2] = analysis[4][5] = "e1";
analysis[6][1] = analysis[6][2] = analysis[6][5] = analysis[7][1] = analysis[7][2] = analysis[7][5] = "e1";
analysis[0][4] = analysis[1][4] = analysis[4][4] = analysis[6][4] = analysis[7][4] = "e2";
analysis[1][0] = analysis[1][2] = analysis[1][3] = analysis[8][0] = analysis[8][2] = analysis[8][3] = "e3";
analysis[8][5] = "e4";
analysis[2][0] = analysis[2][3] = "r2";
analysis[3][2] = analysis[3][3] = "r4";
analysis[5][0] = analysis[5][3] = "r6";
analysis[9][0] = analysis[9][3] = "r1";
analysis[10][0] = analysis[10][3] = "r3";
analysis[11][0] = analysis[11][3] = "r5";
}
/*输出移进还是规约，规约的话输出用到的产生式*/
void print(int into)
{
if (into == 0)
{
cout << "--移进--" << endl;
return;
}
cout << "--按";
switch (into)
{
case 1:cout << "E->E+T"; break;
case 2:cout << "E->T"; break;
case 3:cout << "T->T*F"; break;
case 4:cout << "T->F"; break;
case 5:cout << "F->(E)"; break;
case 6:cout << "F->id"; break;
}
cout << "规约--" << endl;
}
/*为终结符合非终结符编号*/
int NumOfSymbols(char c){
/*switch (c){
case 'a':return 0;
case '+':return 1;
case '*':return 2;
case '(':return 3;
case ')':return 4;
case '#':return 5;
case 'E':return 6;
case 'T':return 7;
case 'F':return 8;
}*/
if (c == 'a'){ return 0; }
if (c == '+'){ return 1; }
if (c == '*'){ return 2; }
if (c == '('){ return 3; }
if (c == ')'){ return 4; }
if (c == '$'){ return 5; }
if (c == 'E'){ return 6; }
if (c == 'T'){ return 7; }
if (c == 'F'){ return 8; }
}
char GetSymbol(int num){
if (num == 0){ return 'a'; }
if (num == 1){ return '+'; }
if (num == 2){ return '*'; }
if (num == 3){ return '('; }
if (num == 4){ return ')'; }
if (num == 5){ return '$'; }
if (num == 6){ return 'E'; }
if (num == 7){ return 'T'; }
if (num == 8){ return 'F'; }
}
int Num[10];//存储数
char *Change(char*a){
int len = strlen(a);//字符串a的长度
char *b = new char[len];//存储字符
int charnum = 0;//记录b中实际有多少字符串
int cur1 = 0;//Num[]的角标
int cur2 = 0;//b[]的角标
for (int i = 0; i < len; i++){
if (a[i] <= 59 && a[i] >= 48){
int num_len = 1;//大于一位数的这个数的长度
int num = 0;//最后记录这个数的大小
b[cur1] = 'a';//遇见的数字，把a放进栈
charnum++;
cur1++;//b的角标向后挪
int curr = i + 1;//curr指向当前处理字符的下一个字符，如果依然是数字那么就值个多位数
/*记录这个多位数的位数*/
while (a[curr] <= 59 && a[curr] >= 48){
num_len++;
curr++;
}
int acc = num_len;//记录循环次数，百位*10*10，千位*10*10*10
for (int j = i; j < i + num_len; j++){
int tempsum = 1;
for (int k = 0; k < acc - 1; k++){
tempsum *= 10;
}
acc--;
num += (a[j] - 48)*tempsum;
}
Num[cur2] = num;//把得到的这个数（或多位数或一位数放入数组）
cur2++;//Num角标后挪
for (int l = 0; l < num_len - 1; l++){ i++; }//多位数有几位就向后挪几位，一位数不用挪
}
else{//不是数字的话直接放入b中
b[cur1] = a[i];
charnum++;
cur1++;
}
}
cout << "该式的原型为：" << endl;
char *c = new char[charnum];//重新存储一下b，因为长度不准确
for (int i = 0; i < charnum; i++){
c[i] = b[i];
cout << c[i] << " ";
}
cout << endl;
cout << "---------------" << endl;
return c;
}
void main(){
string analysis[12][9];
stack<int> s;//字符栈
stack<int> val;//数字栈
int curr = 0;//记录Num中还未放入数字栈的角标
char* input = "(20+6)*5+8$";
cout << "输入表达式：" << input << endl;
char* str = Change(input);
/*cin >> str;*/
int len = strlen(str);
Initial(analysis);
s.push(0);
/*循环中i表示当前处理得输入串中的角标*/
for (int i = 0; i < len;){
int stack_top = s.top();//记录栈顶状态
cout <<"此时栈定状态为："<< stack_top;
cout << " 此时输入字符为："<< str[i] << endl;
int lookahead = NumOfSymbols(str[i]);//记录当前输入串中，正在被处理的字符的标号
/*移进*/
if (analysis[stack_top][lookahead][0] == 's'){
if (analysis[stack_top][lookahead][1] == 's'){
print(0);
s.push(lookahead);
s.push(11);
cout << "将状态11移进栈。" << endl;
i++;
}
else{
print(0);
s.push(lookahead);
s.push(analysis[stack_top][lookahead][1] - '0');
cout << "将状态" << analysis[stack_top][lookahead][1] - '0' << "移进栈。" << endl;
i++;//移进了一个后,就可以看下一个字符了
}
}
/*规约*/
else if (analysis[stack_top][lookahead][0] == 'r'){
int times;//如需规约，弹栈的次数
int NumofNon_Terminal;//需要移进栈的终结符的编号
print(analysis[stack_top][lookahead][1] - '0');//输出规约的式子
switch (analysis[stack_top][lookahead][1] - '0'){
case 1: times = 6; NumofNon_Terminal = NumOfSymbols('E'); break;
case 2: times = 2; NumofNon_Terminal = NumOfSymbols('E'); break;
case 3: times = 6; NumofNon_Terminal = NumOfSymbols('T'); break;
case 4: times = 2; NumofNon_Terminal = NumOfSymbols('T'); break;
case 5: times = 6; NumofNon_Terminal = NumOfSymbols('F'); break;
case 6: times = 2; NumofNon_Terminal = NumOfSymbols('F'); break;
}
for (int j = 0; j < times; j++){
s.pop();
}
int pre_top=s.top();//记录此时的栈顶
cout << "弹栈" << times << "次后,栈顶状态为"<< pre_top << endl;
s.push(NumofNon_Terminal);
char c = GetSymbol(NumofNon_Terminal);//为了输出字符，通过序号找到
cout << "放入"<< c << endl;
/*处理数字栈中的树*/
if (analysis[pre_top][NumofNon_Terminal].size() == 1){
s.push(analysis[pre_top][NumofNon_Terminal][0] - '0');
cout << "将状态" << analysis[pre_top][NumofNon_Terminal][0] - '0' << "移进栈。" << endl;
}
else{
s.push(10);
cout << "将状态10移进栈。" << endl;
}
if (analysis[stack_top][lookahead][1] - '0' == 1){
int temp1 = val.top();
val.pop();
int temp2 = val.top();
val.pop();
val.push(temp1 + temp2);
cout << "弹出了" << temp1 << " " << temp2 << "，放入" << val.top() << endl;
}
if (analysis[stack_top][lookahead][1] - '0' == 3){
int temp1 = val.top();
val.pop();
int temp2 = val.top();
val.pop();
val.push(temp1 * temp2);
cout << "弹出了" << temp1 << " " << temp2 << "，放入" << val.top() << endl;
}
if (analysis[stack_top][lookahead][1] - '0' == 6){
val.push(Num[curr]);
curr++;
cout << "放入" << val.top() << endl;
}
}
/*错误恢复*/
else if (analysis[stack_top][lookahead][0] == 'e'){
cout << "出现错误" << endl;
switch (analysis[stack_top][lookahead][1]){
case '1':{ //期望遇到a,那就把a放进去
s.push(0);
s.push(5);
cout << "缺少运算符,加入a" << endl;
break;
}
case '2':{
//遇见右括号，没有左括号，说明右括号错误
i++;
cout << "不匹配的右括号,将忽略该字符" << endl;
break;
}
case '3':{
//期望遇见运算符,加进+
s.push(1);
s.push(6);
cout << "缺少运算符,加入a" << endl;
break;
}
case '4':{
//提前结束,但期望遇见右括号，那就加入有括号
s.push(4);
s.push(11);
cout << "缺少右括号" << endl;
break;
}
}
}
else{
if (analysis[stack_top][lookahead][0] == 'a'){
cout << "接受"<<endl;
cout << "结果为：" << val.top() << endl;
return;
}
else{
cout << "无法识别,完蛋了！" << endl;
return;
}
}
cout << "--------------------------------------" << endl;
}
}