> On 2 Apr 2020, at 23:49, Konrad Bucheli via perl6-users
> <perl6-users@perl.org> wrote:
> I have a hash with arrays as value. Out of that I wanted to get a flat list
> with all the entries in the value arrays. My first intuitive attempt was to
> use flat, but somehow that only works with an additional map step:
>
> $ raku
> To exit type 'exit' or '^D'
>> my %hash-with-arrays = a => [1,2], b => [2,3]
> {a => [1 2], b => [2 3]}
>> %hash-with-arrays.values.flat
> ([2 3] [1 2])
>> %hash-with-arrays.values>>.map({$_})
> ((2 3) (1 2))
>> %hash-with-arrays.values>>.map({$_}).flat
> (2 3 1 2)
>>
> $ raku -v
> This is Rakudo version 2020.02 built on MoarVM version 2020.02
> implementing Raku 6.d.
> $
>
> How is that explained?
This is because the array inside the hash is inside a container. You can see
this is you use `dd` to show the contents of a key:
> dd %hash-with-arrays<a>
Array %hash-with-arrays = $[1, 2]
Note the $ prefix in the output. This inhibits automatic iteration of the
array. There is a simple way around it:
> %h.values.map: |*
(1 2 2 3)
This slightly line-noisy solution is short for:
> %h.values.map( { $_.Slip } )
(1 2 2 3)
Aka, "slip" the values into a single stream of values, hence getting the result
you wanted
