/**
 * @name 解释器模式
 * @brief: 定义语言的语法表示
 * @note 场景：SQL解析、正则表达式、数学公式计算
 */

class Expression {
public:
    virtual int interpret() = 0;
};

class Number : public Expression {
public:
    Number(int value) : value(value) {}
    int interpret() override { return value; }
private:
    int value;
};

class Add : public Expression {
public:
    Add(Expression* left, Expression* right)
        : left(left), right(right) {}
    int interpret() override {
        return left->interpret() + right->interpret();
    }
private:
    Expression* left;
    Expression* right;
};

// 使用：构建表达式树 (2 + (3 + 4))
Expression* expr = new Add(
    new Number(2),
    new Add(new Number(3), new Number(4))
);

int main()
{
    int result = expr->interpret();  // 输出9
}