Question

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.

Answer 1

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.