c++ - Boost.MultiArray 任意开始和结束索引

Question

我有一个看起来像这样的类。目的是有一个任意的起点和终点，但运算符 [] 映射到索引 0 作为下限。

template <class T>
class Vec : public std::vector<T>
{
public:
    Vec()
    {
        this->reserve(32000);
    }

    Vec(std::string s, int upperbound, int lowerbound)
    {
        SetBounds(s, upperbound, lowerbound);
    }

    void SetBounds(const std::string& s, int upperbound, int lowerbound)
    {
        mys = s;
        ub = upperbound;
        lb = lowerbound;

        std::cout << "resizing Vec for symbol: "
                  << symbol     << " "
                  << upperbound << " "
                  << lowerbound << " "
                  << upperbound - lowerbound << '\n';


        try
        {
           this->resize(ub - lb + 1);
        }
        catch(std::exception& ex)
        {
            std::cout << "Resize Exception: " << ex.what() << "\n";
        }
        catch(...)
        {
            std::cout << "SetBounds exception" << "\n";
        }
    }
public:
    T& operator[] (int idx)
    {
        try
        {
            //std::cout << idx << std::endl;

            return this->at(idx - lb);
        }
        catch(std::exception& ex)
        {
           std::cout << "Access Exception: " << idx << " " << symbol << " " << ex.what() << '\n';
        }
        catch(...)
        {
            std::cout << "Access Exception: " << idx << " "  << symbol << '\n';
        }
    }

private:
    std::string mys;
    int ub;
    int lb;
};

我的问题是，对于 Boost.MultiArray 是否有等效的方法来做到这一点，以便可以为每个维度指定其自己的任意起始和结束索引？

Answer 1

是的。

http://www.boost.org/doc/libs/1_58_0/libs/multi_array/doc/user.html#sec_base

Setting The Array Base

In some situations, it may be inconvenient or awkward to use an array that is zero-based. the Boost.MultiArray components provide two facilities for changing the bases of an array. One may specify a pair of range values, with the extent_range type, to the extent_gen constructor in order to set the base value.

Example

typedef boost::multi_array<double, 3> array_type;
typedef boost::multi_array_types::extent_range range;
// OR typedef array_type::extent_range range;

array_type::extent_gen extents;

// dimension 0: 0-based
// dimension 1: 1-based
// dimension 2: -1 - based
array_type A(extents[2][range(1,4)][range(-1,3)]);

An alternative is to first construct the array normally then reset the bases. To set all bases to the same value, use the reindex member function, passing it a single new index value.