Question

我正在尝试使用boost :: multi_array为c ++中的模板类编写一些与维度无关的代码（尽管如果其他容器/数据结构更好，我会很高兴听到它）

给定一个维度，我想迭代所有其他维度的整个范围，沿所选维度返回1d视图。这是相当简单的，或者至少它似乎来自增强文档。

在编译时已知数组的维度时，我无法弄清楚如何在数组的所有维度上迭代选定的维度。

有关如何执行此操作的建议吗？

Answer 1

通常你可以用boost :: multi_array来做，下面是一些示例代码来创建3D multi_array的2D视图：

#include "boost/multi_array.hpp"
#include <cassert>
#include <iostream>

int main()
{
    typedef boost::multi_array<double, 3> array_type;
    typedef array_type::index index;

    array_type myArray3D(boost::extents[3][4][2]);

    // Assign values to the elements
    int values = 0;
    for (index i = 0; i != 3; ++i)
    {
            for (index j = 0; j != 4; ++j)
            {
                    for (index k = 0; k != 2; ++k)
                    {
                            myArray3D[i][j][k] = values++;
                    }
            }
    }
    // Verify values
    int verify = 0;
    for (index i = 0; i != 3; ++i)
    {
            for (index j = 0; j != 4; ++j)
            {
                    for (index k = 0; k != 2; ++k)
                    {
                            std::cout << "[" << i << "]";
                            std::cout << "[" << j << "]";
                            std::cout << "[" << k << "] = ";
                            std::cout << myArray3D[i][j][k] << std::endl;
                            assert(myArray3D[i][j][k] == verify++);
                    }
            }
    }

    typedef boost::multi_array_types::index_range range;
    array_type::index_gen indices;

    // Create a new view with 2 dimentions fixing the 2nd dimention to 1
    array_type::array_view<2>::type myView =
    myArray3D[indices[range()][1][range()]];
    std::size_t numDims = myView.size();
    std::cout << "numDims = " << numDims << std::endl;

    for (index i = 0; i != 3; ++i)
    {
            for (index j = 0; j != 2; ++j)
            {
                    std::cout << "[" << i << "]";
                    std::cout << "[" << j << "] = ";
                    std::cout << myView[i][j] << std::endl;
            }
    }

    return 0;
}

迭代boost :: multi_array的维度

1 个答案: