Make broadcasted function return Matrix instead of Array of Arrays

General Usage
1

I have a function returning a (fixed and known-length) array for some input:

function bitlevels(n, x)
    l = reverse(digits(x, base=2))
    [repeat([0], n - length(l)); l]
end

When broadcasting this function to a vector (e.g., bitlevels.(5, [0, 2, 3, 5])), I get an Array of Arrays instead of a Matrix.

I’d assume this has performance penalties due to pointer indirection, when those arrays become large. How can I change my implementation, so that a Matrix instead of an Array of Arrays is returned?

(Or is this actually a bad idea and I’m better off working on Arrays of Arrays?)

2

if your function returns a vector, then broadcasting (by construction) can only return a vector of vector. you either need to cat the resul manually, or you need to map reduce and cat along the way

3

Okay, thanks. So I’ll check the performance, how copying to a matrix compares to working on arrays of arrays.