What's the "**" operator in perl? I most of the time use R for math, not
familiar with this operation.
Thanks
On Sun, Oct 31, 2021 at 3:38 AM Sean McAfee <eef...@gmail.com> wrote:
> Recently I was golfing the "hyperfactorial," defined for a number 𝑛 as
> 𝑛**𝑛 × (𝑛-1)**(𝑛-1) × (𝑛-2)**(𝑛-2) × ... × 1. I created a quite
> concise Raku function:
>
> { [*] [\*] $_...1 }
>
> The only problem was that this function returns zero for a zero input,
> whereas the hyperfactorial of 0 is supposed to be 1. Of course I could
> have just handled zero as a special case, but I hoped to find something
> comparably short. After a bit of thought I tried reversing both the range
> and the operator:
>
> { [*] [\R*] 1..$_ }
>
> It worked! But I couldn't quite see how. * is commutative, so isn't it
> exactly the same as R*?
>
> It turns out, in Raku it isn't quite the same. On the operators page, I
> found that the R metaoperator produces an operator that reverses the order
> of the arguments, but *also* has the opposite associativity. So, for
> example, [\R*] 1..4 reduces from the right, producing the list (4, 12, 24,
> 24). Somehow I had formed the idea that Raku operators are left-, right-,
> or list-associative, but I was wrong.
>
> Anyway, pretty cool!
>
>
