C ++對二進制表達式無效的操作數（“ IOperand *”和“ IOperand *”）

Question

我知道這個問題已經問了很多遍了，但是我找不到我的問題的答案，

我有這個運算符重載：

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

從此界面：

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() {}
};

該接口被6個類“ Int8”，“ Int16”，“ Int32”，“ Float”，“ Double”，“ BigDecimal”繼承和覆蓋，如下所示：

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;
};

這是在Int8類中寫這個operator +的方法

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));
}

對我來說，到這里為止看起來還不錯，但是當我嘗試像這樣使用operator +時：

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

IOperand *result = first + second;

我有錯誤：

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

在

IOperand *result = first + second;

我很難弄清楚發生了什么，請幫助

ps：stack_是std :: stack，是的，它不為空

Answer 1

操作員+需要根據您的原型提供參考

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

但是您嘗試添加指針：

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

IOperand *result = first + second;

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