将多维数组转换为 C++ 中的指针

Converting multidimensional arrays to pointers in c++(将多维数组转换为 C++ 中的指针)

问题描述

我有一个如下所示的程序:

I have a program that looks like the following:

double[4][4] startMatrix;
double[4][4] inverseMatrix;
initialize(startMatrix) //this puts the information I want in startMatrix

我现在想计算startMatrix的逆并将其放入inverseMatrix.为此，我有一个库函数，其原型如下:

I now want to calculate the inverse of startMatrix and put it into inverseMatrix. I have a library function for this purpose whose prototype is the following:

void MatrixInversion(double** A, int order, double** B)

将 A 的倒数放入 B 中.问题是我需要知道如何将 double[4][4] 转换为 double** 以提供给函数.我试过只是用明显的方式"来做:

that takes the inverse of A and puts it in B. The problem is that I need to know how to convert the double[4][4] into a double** to give to the function. I've tried just doing it the "obvious way":

MatrixInversion((double**)startMatrix, 4, (double**)inverseMatrix))

但这似乎不起作用.这真的是正确的做法吗?

but that doesn't seem to work. Is that actually the right way to do it?

推荐答案

不，没有正确的方法可以专门解决这个问题.double[4][4] 数组不能转换为 double ** 指针.这是实现二维数组的两种替代的、不兼容的方法.需要改变一些东西:函数的接口，或者作为参数传递的数组的结构.

No, there's no right way to do specifically that. A double[4][4] array is not convertible to a double ** pointer. These are two alternative, incompatible ways to implement a 2D array. Something needs to be changed: either the function's interface, or the structure of the array passed as an argument.

执行后者的最简单方法，即使您现有的 double[4][4] 数组与函数兼容，是创建 double 类型的临时索引"数组*[4] 指向每个矩阵中每一行的开头

The simplest way to do the latter, i.e. to make your existing double[4][4] array compatible with the function, is to create temporary "index" arrays of type double *[4] pointing to the beginnings of each row in each matrix

double *startRows[4] = { startMatrix[0], startMatrix[1], startMatrix[2] , startMatrix[3] };
double *inverseRows[4] = { /* same thing here */ };

并传递这些索引"数组

MatrixInversion(startRows, 4, inverseRows);

一旦函数完成工作，您可以忘记 startRows 和 inverseRows 数组，因为结果将放入您原来的 inverseMatrix正确排列.

Once the function finished working, you can forget about the startRows and inverseRows arrays, since the result will be placed into your original inverseMatrix array correctly.

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