I have a generic function which will take in a boost::multi_array of dimension size N. I need to take slices along the M'th < N dimension (known at compile time). I can't figure out how to do this with the multi_array library and associated ranges/array_views. Is there another way to do this rather than building a boost::indices object directly? Besides the sliced dimension, I will always want the entire ranges for the other ones.
I believe the problem is that the index_gen object needs different types as we build the indices in parts. The following code shows what a hardcoded example would look like for N = 4 and M = 3
const std::size_t n_1 = 3;
const std::size_t n_2 = 4;
const std::size_t n_3 = 5;
const std::size_t n_4 = 6;
typedef boost::multi_array<double, 4> array_type;
array_type vals(boost::extents[n_1][n_2][n_3][n_4]);
//...fill the array...
typedef boost::multi_array_types::index_range range;
typedef boost::multi_array_types::index_gen index_gen_type;
//Trying to do this dynamically instead, but in pieces. Note that you need the different autos at each stage since you can't build an index directly?
auto slice_indices2 = boost::indices[range(0,n_1)][range(0,n_2)]; //first dimensions
auto slice_indices3 = slice_indices2[1]; //Slice dimension.... for the 2nd index.
auto slice_indices4 = slice_indices3[range(0,n_4)]; //last dimensions
auto vals_slice3 = vals[ slice_indices4 ]; //Take slices with the final object. This is a proper multi_array view
cout << vals_slice3[0][0][0] << endl;
Thanks, Jesse