帮我写一段消除普通文法的直接左递归和间接左递归的c++代码

消除普通文法的直接左递归和间接左递归的 C++ 代码如下：

// 消除直接左递归
void eliminate_direct_left_recursion(vector<string>& productions, char non_terminal) {
    vector<string> new_productions;
    vector<string> old_productions;
    for (string production : productions) {
        if (production[0] == non_terminal) {
            old_productions.push_back(production);
        } else {
            new_productions.push_back(production);
        }
    }
    if (old_productions.size() == 0) {
        return;
    }
    string new_non_terminal = string(1, non_terminal) + "'";
    new_productions.push_back(new_non_terminal + " -> ε");
    for (string old_production : old_productions) {
        string new_production = old_production.substr(1) + new_non_terminal;
        new_productions.push_back(new_production);
    }
    new_productions.push_back(new_non_terminal + " -> " + old_productions[0].substr(1) + new_non_terminal);
    productions = new_productions;
}

// 消除间接左递归
void eliminate_indirect_left_recursion(map<char, vector<string>>& grammar) {
    vector<char> non_terminals;
    for (auto it = grammar.begin(); it != grammar.end(); it++) {
        non_terminals.push_back(it->first);
    }
    int n = non_terminals.size();
    for (int k = 0; k < n; k++) {
        char A = non_terminals[k];
        for (int i = 0; i < k; i++) {
            char B = non_terminals[i];
            for (int j = 0; j < grammar[A].size(); j++) {
                string production = grammar[A][j];
                if (production[0] == B) {
                    vector<string> new_productions;
                    for (string B_production : grammar[B]) {
                        string new_production = B_production + production.substr(1);
                        new_productions.push_back(new_production);
                    }
                    grammar[A].erase(grammar[A].begin() + j);
                    grammar[A].insert(grammar[A].end(), new_productions.begin(), new_productions.end());
                    j += new_productions.size() - 1;
                }
            }
        }
        eliminate_direct_left_recursion(grammar[A], A);
    }
}

其中，`eliminate_direct_left_recursion`函数用于消除一个非终结符的直接左递归，`eliminate_indirect_left_recursion`函数用于消除文法中的间接左递归。两个函数均接受一个文法的数据结构，`vector<string>`表示一个非终结符的产生式集合，`map<char, vector<string>>`表示整个文法。在实际使用时，需要先将文法转换成这种数据结构。