Autoarraying

Over on Reddit zeekar wasn’t too happy about Raku’s love of Seq. It’s immutability can be hindering indeed.

my @nums = [ [1..10], ];
@nums[0] .= grep: * % 2;
@nums[0].push(11); # We can't push to a Seq.

I provided a solution I wasn’t happy with. It doesn’t DWIM and is anything but elegant. So while heavily digesting on my sofa (it is this time of the year), the problem kept rolling around in my head. At first I wanted to wrap Array.grep(), but that would be rather intrusive and likely break Rakudo itself. After quite a bit of thinking, I ended up with the question. How can I have indexable container (aka Array) that will turn each value on assignment into an (sub-)Array?

my Array() @foo = [ 1..10, ];
dd @foo;
# Array[Array(Any)] @foo = Array[Array(Any)].new($[1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
@foo[0] .= grep: * % 2;
@foo[1] = 42;
dd @foo;
# Array[Array(Any)] @foo = Array[Array(Any)].new($[1, 3, 5, 7, 9], $[42])

The answer is obvious. By telling the compiler what I want! Coersion-types have become really hard to distinguish from magic.

I wish you all a Merry Christmas and the very best questions for 2024.