重载模板运算符

Question

我正在尝试在我的模板 Vector 类上重载 += 运算符。

template<unsigned int dimensions, typename TValue>
class Vector
{
private:
    std::array<TValue, dimensions> m_values;
public:
    Vector(){
        for (int i = 0; i < dimensions; i++){
            m_values[i] = TValue();
        }
    };
    Vector(std::array<TValue, dimensions> elements){
        for (int i = 0; i < dimensions; i++){
            m_values[i] = elements[i];
        }
    };
    
    inline void set(VectorDimensions dimension, TValue value){
        m_values[dimension] = value;
    };
    
    inline TValue get(VectorDimensions dimension) const{
        return m_values[dimension];
    };

    inline unsigned int getSize() const{
        return dimensions;
    };

    const std::array<TValue, dimensions> getValues() const{
        return m_values;
    };

    friend ostream& operator<<(ostream& os, const Vector<dimensions, TValue>& vt) {
        array<TValue, dimensions> values = vt.getValues();
        os << '[';
        for (unsigned int i = 0; i < vt.getSize(); i++){
            os << values[i] << values[i+1] ? ", " : "";
        }
        os << ']';
        return os;
    };

    friend Vector<dimensions, TValue>& operator+=(const Vector<dimensions, TValue>& vt) {
        array<TValue, dimensions> values = vt.getValues();
        for (unsigned int i = 0; i < vt.getSize(); i++){
            m_values[i] += values[i];
        }
        return *this;
    };

};

为 += 运算符添加重载后，我收到许多以下错误：

错误 C2805：二进制 'operator +=' 的参数太少

错误 C4430：缺少类型说明符 - 假定为 int。注意：C++ 不支持 default-int

错误 C2334：'{' 之前的意外标记；跳过明显的函数体。

错误 C2238：';' 前面的意外标记

语法错误：缺少';'在'之前

错误 C2143：语法错误：缺少 ';'在'++'之前

错误 C2143：语法错误：在 ';' 之前缺少 ')'

错误 C2059：语法错误：'return'

错误 C2059：语法错误：'for'

错误 C2059：语法错误：')'

解释为什么或如何实际导致这些错误是由我做错了什么可能是有用的。谢谢

Answer 1

我能够通过从 += 运算符定义之前删除friend 关键字来停止错误。根据这个页面http://en.cppreference.com/w/cpp/language/operators

class X {
 public:
  X& operator+=(const X& rhs) // compound assignment (does not need to be a member,
  {                           // but often is, to modify the private members)
    /* addition of rhs to *this takes place here */
    return *this; // return the result by reference
  }

  // friends defined inside class body are inline and are hidden from non-ADL lookup
  friend X operator+(X lhs,       // passing first arg by value helps optimize chained a+b+c
                    const X& rhs) // alternatively, both parameters may be const references.
  {
     return lhs += rhs; // reuse compound assignment and return the result by value
  }
};

这就是 + 和 += 运算符的重载方式。