C ++运算符+和运算符+ =重载 [英] C++ operator+ and operator+= overloading

问题描述

我在c ++中实现自己的矩阵类，以帮助我发展我对语言的理解。我读某处，如果你有一个工作的+ =运算符，在你的+运算符中使用它。这是我得到的：

 模板< class T& 
 const Matrix< T> Matrix< T> :: operator +（const Matrix& R）{
 
 Matrix< T> copy（* this）; 
 return copy + = R; 
} 
  

这里是+ =运算符重载：

 模板< class T> 
 const Matrix< T> Matrix< T> :: operator + =（const Matrix& second_matrix）{
 //了解如何抛出错误... 
 if（rows！= second_matrix.getNumRows cols！= second_matrix.getNumCols（））{throwDimension mismatch。;} 
 int i，j; 
 for（i = 0; i< rows; i ++）{
 for（j = 0; j  data [i] [j] + = second_matrix .get（i，j）; 
} 
} 
 return * this; 
} 
  

我可以使用+ =只是罚款（例如，a + = b;返回没有错误）。但是调用+运算符（例如，a = b + c;）会返回：

  test.cpp.out（77055） ：对象的***错误0x300000004：未释放指针
  

为了完整性，这里是我的析构函数：

  template< class T> 
 Matrix< T> ::〜Matrix（）{
 for（int i = 1; i< rows; i ++）{
 delete [] data [i] } 
 delete [] data; 
} 
  

我一直使用C ++几年，有时难以跟踪指针。我希望这是正常的...
任何帮助将是伟大的。谢谢！

编辑：这里是我的拷贝构造函数。它设置为释放数据数组，但我删除了。现在我得到分割错误。

 模板< class T& 
 Matrix< T> :: Matrix（const Matrix< T>& second_matrix）{
 
 rows = second_matrix.getNumRows（）; 
 cols = second_matrix.getNumCols（）; 
 data = new T * [rows]; 
 
 int i，j; 
 for（i = 0; i< rows; i ++）{
 data [i] = new T [cols]; 
} 
 for（i = 0; i  for（j = 0; j  data [i] j] = second_matrix.get（i，j）; 
} 
} 
 
} 
  

方案

运算符+（）不应返回引用类型，因为它是一个保存操作结果的新（本地声明的） p>

I'm implementing my own matrix class in c++ to help me develop my understanding of the language. I read somewhere that if you've got a working += operator, to use it in your + operator. So that's what I've got:

template <class T>
const Matrix<T>& Matrix<T>::operator+(const Matrix<T> &R){

    Matrix<T> copy(*this);
    return copy += R;
}

And here is the += operator overload:

template <class T>
const Matrix<T>& Matrix<T>::operator+=(const Matrix<T> & second_matrix){
    //Learn how to throw errors....
    if (rows != second_matrix.getNumRows() || cols != second_matrix.getNumCols()){throw "Dimension mismatch.";}
    int i,j;
    for (i = 0; i < rows; i++){
        for (j = 0; j < cols; j++){
            data[i][j] += second_matrix.get(i,j);
        }
    }
    return *this;
}

I can use the += just fine (eg, a += b; returns no errors). But calling the + operator (eg, a = b + c;) returns :

test.cpp.out(77055) malloc: *** error for object 0x300000004: pointer being freed was not allocated

Just for completeness, here's my destructor:

template <class T>
Matrix<T>::~Matrix(){
    for (int i = 1; i < rows; i++){
        delete[] data[i]; }
    delete[] data;
}

I've been using C++ for a couple years on and off, and still have trouble sometimes keeping track of pointers. I hope that's normal... Any help would be great. Thanks!

EDIT: here's my copy constructor. It was set to free the data arrays but i removed that. now I get segmentation faults.

template <class T>
Matrix<T>::Matrix(const Matrix<T>& second_matrix){

    rows = second_matrix.getNumRows();
    cols = second_matrix.getNumCols();
    data = new T*[rows];

    int i,j;
    for (i = 0; i < rows; i++){
        data[i] = new T[cols];
    }
    for (i = 0; i < rows; i++){
        for (j = 0; j < cols; j++){
            data[i][j] = second_matrix.get(i,j);
        }
    }

}

解决方案

operator+() should not return a reference type as it is a new (locally declared) instance that holds the result of the operation.

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