动态分配多维数组的方法 [英] A way of allocating multidimensional arrays dynamically

问题描述

致敬..

我在一本书中学习多维数组的动态分配，我找到了一些方法，现在没有问题了。
但是这本书的作者向我们展示了一种方法，但它不能正常工作。这是：

  pbeans = new double [3] [4]; //为3x4数组分配内存
  

这是错误：

 错误C2440：'='：无法从'int（*）[4]'转换为'int *'
  
 
 
 
我应该如何定义 pbeans （如果这种类型的编码合法）？
 
 
解决方案   / div> 
这在我的阵列常见问题中列出：
  double（* pbeans）[4]; 
 pbeans = new double [3] [4]; 
 
 // ... 
 
 delete [] pbeans; 
 
对于C declarator impaired，你可以使用typedef更容易阅读：
  typedef double row [4]; 
 
 row * pbeans; 
 pbeans = new row [3]; 
 
 // ... 
 
 delete [] pbeans; 
 
但是在C ++中，我们更喜欢用裸指针的RAII容器：
  #include< vector> 
 #include< array> 
 
 std :: vector< std :: array< double，4> >豆类（3）; 
  
注意完全没有 delete [] 这使得此解决方案是异常安全的。
 
salute..

I am learning dynamic allocations for multidimensional arrays in a book and I found some ways for that, And now haven't problem in it.
But the author of the book shows us a way, but it doesn't work correctly. It is this:
pbeans = new double [3][4];         // Allocate memory for a 3x4 array
And this is the error:
error C2440: '=' : cannot convert from 'int (*)[4]' to 'int *'
how should i define pbeans ( if this type of coding is legal)?

and what is the problem exactly?

Regards.
解决方案
This is covered in my FAQ on arrays:
double (*pbeans)[4];
pbeans = new double[3][4];

// ...

delete[] pbeans;
For the "C declarator impaired", you could make that more readable with a typedef:
typedef double row[4];

row *pbeans;
pbeans = new row[3];

// ...

delete[] pbeans;
But in C++, we prefer RAII containers over raw pointers:
#include <vector>
#include <array>

std::vector<std::array<double, 4> > beans(3);
Note the complete absence of delete[] which makes this solution exception-safe.

                        
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