The fundamental problem here seems to be the imprint of Perl's
behaviour on the mental model. Assigning arrays flattens them into a
list of their contents, which then gets used as input to the
assignment. That means that more complicated structures, such as
arrays of arrays need some faking.
Raku approaches arrays as thingies in their own right, so the
subconcious assumptions are no longer valid. Vocalising the actions
of the code, (even if just internally) will probably overlay the old
model in time, (though the palimpsest may show through in unguarded
momants).
On 1/19/21, Ben Davies <kai...@outlook.com> wrote:
> On 2021-01-19 2:18 p.m., Brian Duggan wrote:
>> Hi Folks,
>>
>> I ran into this situation today, which seems counterintuitive:
>>
>> my @one = 1,2,3;
>> my @two = 4,5,6;
>> my @both = @one,@two;
>> my @first = @both[0];
>> say @one.raku;
>> say @first.raku;
>>
>> output:
>>
>> [1, 2, 3]
>> [[1, 2, 3],]
>>
>> I was expecting @first and @one to be the same.
>> I discovered that I could instead write either of these --
>>
>> my (@first) = @both[0];
>> my @first := @both[0];
>>
>> or I could change the @both assignment to be
>>
>> my @both := @one, @two;
>>
>> ..but I wonder if there's an idiomatic approach -- or
>> way of thinking about this -- that makes this flow more
>> intuitive.
>>
>> thanks
>> Brian
>
> Arrays always containerize their values with Scalar ("itemize"). This
> means that when they contain arrays as values, each array will get
> treated like a singular value that happens to be an Array instead of an
> array of values like they normally would elsewhere.
>
> Lists keep their values' containers as-is. These are what the , operator
> returns by default, so one way to leverage containers here is to bind to
> @both like you already discovered:
>
> my @both := @one, @two;
>
> Another is to type @both as a List and assign:
>
> my @both is List = @one, @two;
>
> But List lacks some of the luxuries Array provides over it, such as
> mutability and typed values. What I'd do here is decontainerize @both[0]
> with the <> postfix operator so @both's Array typing can be kept:
>
> my @first = @both[0]<>;
>
>
