On Mon, Nov 3, 2025 at 1:31 PM ToddAndMargo via perl6-users <
[email protected]> wrote:
> I guess I am asking what the flattening does.
>
It passes the elements of an array as separate parameters to a function,
rather than passing the array itself as a single parameter.
my @nums = 3, 4, 5;
sub show($x, $y, $z) { say "Got $x, $y, and $z" }
show(1, 2, @nums); # Got 1, 2, and 3 4 5
show(|@nums); # Got 3, 4, and 5
But a function that takes a slurpy array parameter flattens its arguments
automatically, making it pointless to explicitly flatten with a pipe:
sub show2(*@args) { say "Got @args.join(', ')" }
show2(1, 2, @nums); # Got 1, 2, 3, 4, 5
show2(@nums); # Got 3, 4, 5
show2(|@nums); # Got 3, 4, 5
This is why in my other recent response to you, I was able to say this:
my $p = run <ls -la>, dir(test => *.ends-with('.raku'));
And I didn't need to say this, even though it also works:
my $p = run |<ls -la>, |dir(test => *.ends-with('.raku'));
It's because run takes a slurpy list of arguments.
Why is this proper
> my $proc = run(@x, :err, :out)
>
> and this is not
> my $proc = run(@x, :err, :out)
>
Well, I mean...those are identical. But assuming you meant to write |@x in
the second one, it's not "proper" for the same reason this is improper:
my $y = (+$x) ** (+2) - (+5) * (+$x) + (+1);
...compared to:
my $y = $x ** 2 - 5 * $x + 1;
While functionally equivalent, the first is riddled with pointless
complications that will leave a human reader scratching their head.
