重载[] []运算符 [英] overloading [][] operators in c++

问题描述

我在c ++中编写一个矩阵3x3类。<​​/ p>

glm :: mat3提供通过 [] [] operator 语法。

eg myMatrix [0] [0] = 1.0f; 会将第一行第一列条目设置为 1.0f 。

我想提供类似的访问。我如何重载 [] []运算符 s？

错误：

运算符名称必须声明为函数

  const实数运算符[] []（int row，int col）const 
 {
 //应该为超出范围索引
 return（（row> = 0&& row< = 2）&&（col> = 0&& col< = 2） _data [row] [col]：0.0f; 
} 
  

重载此运算符的正确方法是什么？

解决方案

没有运算符 [] [] ，因此您需要重载 [] 运算符两次：一次在矩阵上，返回 / a>对象，对于返回的代理行为一次：

  // Matrix的运算符[] 
 const row_proxy operator []（int row）const 
 {
 return row_proxy（this，row）; 
} 
 //代理的运算符[] 
 const实数运算符[]（int col）const 
 {
 //代理存储指向矩阵的指针，到第一[]运算符
 return（（this-> row> = 0&& this-> row< = 2）&&（col> = 0&& col = 2））？ this-> matrix-> _data [this-> row] [col]：0.0f; 
} 
  

I'm writing a matrix 3x3 class in c++.

glm::mat3 provides access to matrix data through the [][] operator syntax.
e.g. myMatrix[0][0] = 1.0f; would set the first row, first column entry to 1.0f.

I'd like to provide similar access. How can I overload the [][] operators?

I've tried the following, but I get errors:

operator name must be declared as a function

const real operator[][](int row, int col) const
{
    // should really throw an exception for out of bounds indices
    return ((row >= 0 && row <= 2) && (col >= 0 && col <= 2)) ? _data[row][col] : 0.0f;
}

What's the correct way to overload this operator?

解决方案

There is no operator [][], so you need to overload the [] operator twice: once on the matrix, returning a surrogate object for the row, and once for the returned surrogate row:

// Matrix's operator[]
const row_proxy operator[](int row) const
{
    return row_proxy(this, row);
}
// Proxy's operator[]
const real operator[](int col) const
{
    // Proxy stores a pointer to matrix and the row passed into the first [] operator
    return ((this->row >= 0 && this->row <= 2) && (col >= 0 && col <= 2)) ? this->matrix->_data[this->row][col] : 0.0f;
}

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