Recursivly flatten a multidimensional array

Question

What's the shortest way to flat a multidimensional array?
Here's some examples of what I mean:

# 2D array
my @a = [1,2],[3,4];
say @a».Slip.flat;                # prints (1 2 3 4)
# 3D array
my @b = [[1,2],[3,4]],[[5,6],[7,8]];
say @b».Slip».flat».Slip.flat;    # prints (1 2 3 4 5 6 7 8)
                                  # but needs to know how many dimensions
                                  # there are to flatten

Is it possible to recursively flatten an array of arrays such as @b without writing a sub which recursively descends into it or having any knowledge of the number of its dimensions?
I'm asking this because I trust the compiler (now or in a future implementation) to be able to optimize more an operator-based solution than a sub.

Answer 1

Not sure if there's a more compact way, but

say do gather @b.deepmap(*.take);

should do it.

If you do not care for the order of the flattened result,

say do gather @b>>.take;

might also be an option, though it 'feels' wrong to me to (ab)use hyper operators for side effects...

---

Until proper handling of HyperWhatever slicing suggested by raiph arrives in core, you could add your own sugar @b[**] covering this specific use case via

multi sub postcircumfix:<[ ]>(\SELF, HyperWhatever:D $, *% where !*) {
    gather SELF.deepmap(*.take);
}