如何在c++中创建Backus Naur形式的规则？

#include <iostream>
#include <string>

struct Rule {
    std::string nonTerminal;
    std::string production;
};

int main() {
    Rule rule1 = {"<expression>", "<term> + <expression> | <term>"};
    Rule rule2 = {"<term>", "<factor> * <term> | <factor>"};
    Rule rule3 = {"<factor>", "( <expression> ) | <number>"};

    std::cout << "Expression Rule: " << rule1.nonTerminal << " -> " << rule1.production << std::endl;
    std::cout << "Term Rule: " << rule2.nonTerminal << " -> " << rule2.production << std::endl;
    std::cout << "Factor Rule: " << rule3.nonTerminal << " -> " << rule3.production << std::endl;

    return 0;
}