Understanding the Boost MultiArray parameters

Question

This is from the Boost docs and compiles without problems.

#include "boost/multi_array.hpp"

int main () {
    // Create a 3D array that is 3 x 4 x 2
    typedef boost::multi_array<double,3> array_type;
    typedef array_type::index index;
    array_type A(boost::extents[3][4][2]);
    return 0;
}

My question is: What is the second template parameter? It's not clear to me from the documentation. This code will only compile if it is set to 3.

Answer 1

It's how many dimensions you need.

boost::extents[3][4][2] // we use 3 dimensions

So if you change this number, you'll have to change this line to.

Answer 2

It is the 'Numeric Dimension' --- i.e. the number of dimensions of your array: three because you have three subscripts on your boost::extents.

Answer 3

It is the number of dimension of the array:

you have change accordingly the ctor call :

array_type A(boost::extents[3][4]);