I want to write a function that operates on one-dimensional multi_array's and use it to modify the columns of a two-dimensional multi_array. I thought that this would be a straightforward application of slicing, i.e., views with dimensional reduction.

Any suggestions?

Attached version of it working, I think.   Not quite what you had in mind since my attachment includes saves the view as a temporary and then passes the view by reference to the function fill_array.