Hello,

Let’s assume I have a two-dimensional array and the list of Cartesian indices which allow me to extract some subset of the array elements:

```
A = zeros((6, 9))
ci = CartesianIndices((2:2:6, 3:3:9))
A[ci]
```

Now, having `ci`

, how I can extract the Cartesian indices which correspond separately to the first and second dimensions of the array? If I will define them manually, they will be

```
ci1 = CartesianIndices((2:2:6,))
ci2 = CartesianIndices((3:3:9,))
A[ci1, :]
A[:, ci2]
```

And the other way around, having `ci1`

and `ci2`

, how I can merge them into the original `ci`

?

The last question is related to my earlier post https://discourse.julialang.org/t/combine-cartesianindices-for-effective-cuda-kernels/

Thank you.