Simple casting?

[Taylor R Hillegeist]

On Tuesday, 26 November 2019 at 23:29:12 UTC, Ali Çehreli wrote:
> On 11/26/19 2:08 PM, Taylor R Hillegeist wrote:> On Tuesday, 26 
> November 2019 at 16:33:06 UTC, Timon Gehr wrote:
> >>     int[][] y=x.chunkBy!((a,b)=>a==b).map!array.array;
> >
> >
> > how did you know to do that?
> std.array.array pulls all elemenst of a range and places them 
> inside an array. That is eager but sometimes necessary work. 
> For example, std.algorithm.sort cannot sort just any range 
> because it needs the elements to be layed out as array elements:
>
>   someAlgorithmRange.sort;      <-- Does not work
>   someAlgorithmRange.array.sort <-- Works
>
> Ali

I suppose I'm asking here how did he know to use:
.map!array.array

I in my mind I thought that
.array
would have been enough, it seems like it when looking at the 
original error:

GetAllTriplesExtractFileIrqSplit.d(83):

Error: cannot implicitly convert expression 
`chunkBy(irqSortedSet)` of type

`ChunkByImpl!(__lambda4, ProbePoint[3][])`  <<Its almost to the 
final form
to
`ProbePoint[3][][]`

does this have to do with the collection depth?