C ++二进制表达式的无效操作数（'IOperand *'和'IOperand *'）

Question

我知道问题已被多次询问，但我无法找到问题的答案，

我有这个运算符重载：

virtual IOperand *operator+(const IOperand &rhs) const = 0; //sum

来自这个界面：

class IOperand
{
  public:
    virtual std::string toString() const = 0; //stringthatrepresentstheinstance

    virtual eOperandType getType() const = 0; //returnsthetypeofinstance

    virtual IOperand *operator+(const IOperand &rhs) const = 0; //sum
    virtual IOperand *operator-(const IOperand &rhs) const = 0; //difference
    virtual IOperand *operator*(const IOperand &rhs) const = 0; //product
    virtual IOperand *operator/(const IOperand &rhs) const = 0; //quotient
    virtual IOperand *operator%(const IOperand &rhs) const = 0; //modulo

    virtual ~IOperand() {}
};

此接口由6个类“Int8”，“Int16”，“Int32”，“Float”，“Double”，“BigDecimal”继承并覆盖：

class Int8 : public IOperand
{
  private:
    std::string valueUnmodified;
    int8_t value;

  public:
    Int8(std::string my_value);
    virtual ~Int8();
    virtual std::string toString() const;
    virtual eOperandType getType() const;
    virtual IOperand *operator+(const IOperand &rhs) const;
    virtual IOperand *operator-(const IOperand &rhs) const;
    virtual IOperand *operator*(const IOperand &rhs) const;
    virtual IOperand *operator/(const IOperand &rhs) const;
    virtual IOperand *operator%(const IOperand &rhs) const;
};

以下是如何在Int8类中编写此运算符+

IOperand *Int8::operator+(const IOperand &rhs) const
{
    if (rhs.getType() != eOperandType::INT8)
        throw avm::AvmError("Operator error");
    int8_t nb;
    nb = std::stoi(rhs.toString());
    int8_t result;
    result = this->value + nb;

    return new Int8(std::to_string(result));
}

对我来说，直到这里看起来还不错，但当我尝试使用运算符+时：

IOperand *first = stack_.top();
IOperand *second = stack_.top();

IOperand *result = first + second;

我有错误：

invalid operands to binary expression ('IOperand *' and 'IOperand *')

在

IOperand *result = first + second;

我很难弄清楚发生了什么，请帮助

ps：stack_是一个std :: stack，是的，它不是空的

Answer 1

operator +需要根据原型

引用

   virtual IOperand *operator+(const IOperand &rhs) const;

但是你尝试添加指针：

IOperand *first = stack_.top();
IOperand *second = stack_.top();

IOperand *result = first + second;

// should be 
IOperand *result = *first + *second;